Morphology of neurons and axon terminals associated with descending and ascending pathways of the lateral forebrain bundle in Rana esculenta

Summary The cells of origin of afferent and efferent pathways of the lateral forebrain bundle were studied with the aid of the cobalt-filling technique. Ascending afferents originated from the lateral thalamic nucleus, central thalamic nucleus, posterior tuberculum and the cerebellar nucleus. They terminated in the anterior entopeduncular nucleus, amygdala and the striatum. Telencephalic projection neurons, which are related to the lateral forebrain bundle, were located mainly in the ventral striatum and the anterior entopeduncular nucleus, but were not so numerous in the dorsal striatum. Irrespective of their location, most of the neurons projecting axons into the lateral forebrain bundle had piriform or pyramidal perikarya. Long apical dendrites usually arborized in a narrow space, whereas widely arborizing secondary dendrites originated from short dendritic trunks. The other neurons that contributed to the lateral forebrain bundle were fusiform or multipolar cells. Striatal efferents terminated in the pretectal area and in the anterodorsal, anteroventral and posteroventral tegmental nuclei.     

Retinopetal neuronal system in the brain of an air-breathing teleost fish,Channa punctata

Summary Retinopetal neurons were visualised in the telencephalon and diencephalon of an air-breathing teleost fish, Channa punctata, following administration of cobaltous lysine to the optic nerve. The labelled perikarya (n=45–50) were always located on the side contralateral to the optic nerve that had received the neuronal tracer. The rostral-most back-filled cell bodies were located in the nucleus olfactoretinalis at the junction between the olfactory bulb and the telencephalon. In the area ventralis telencephali, two groups of telencephaloretinopetal neurons were identified near the ventral margin of the telencephalon. The rostral hypothalamus exhibited retrogradely labelled cells in three discrete areas of the lateral preoptic area, which was bordered medially by the nucleus praeopticus periventricularis and nucleus praeopticus, and laterally by the lateral forebrain bundle. In addition to a dorsal and a ventral group, a third population of neurons was located ventral to the lateral forebrain bundle adjacent to the optic tract. The dorsal group of neurons exhibited extensive collaterals; a few extended laterally towards the lateral forebrain bundle, whereas others ran into the dorsocentral area of the area dorsalis telencephali. A few processes extended via the anterior commissure into the telencephalon ipsilateral to the optic nerve that had been exposed to cobaltous lysine. However, the ventral cell group did not possess collaterals. In the diencephalon, retinopetal cells were visualised in the nucleus opticus dorsolateralis located in the pretectal area; these were the largest retinopetal perikarya of the brain. The caudal-most nucleus that possessed labelled somata was the retinothalamic nucleus; it contained the largest number of retinopetal cells. The limited number of widely distributed neurons in the forebrain, some with extensive collaterals, might participate in functional integration of different brain areas involved in feeding, which in this species is influenced largely by taste, not solely by vision.     

LOCALIZATION OF GABAERGIC, CHOLINERGIC AND AMINERGIC STRUCTURES IN THE MESOLIMBIC SYSTEM

Abstract— The localization of cholinergic, GABAergic and aminergic structures in the 'mesolimbic' system has been discussed from studies on the topographical distribution of choline acetyltransferase, glutamate decarboxylase and aromatic amino acid decarboxylase in normal rat brain and in brains hemitransected at the level of globus pallidus. The structures analysed included nucleus accumbens, olfactory tubercle, septum, medial forebrain bundle, striatum, substantia nigra, ventral tegmental area and nucleus interpeduncularis.
Choline acetyltranferase was highly concentrated in the nucleus interpeduncularis, but it did also exhibit considerable activity in the nucleus accumbens, the olfactory tubercle and the striatum. The activities did not change after hemitransection. Aromatic amino acid decarboxylase was highly concentrated in the ventral tegmental area, but high activities were also found in the striatum, the nucleus accumbens, the olfactory tubercle and the pars compacta of the substantia nigra. The activity decreased in all areas rostral to the hemitransection. Glutamate decarboxylase was highly concentrated in the dopamine innervated regions, moreso in the limbic structures than in the striatum. Much higher activity was found in the substantia nigra than in the ventral tegmental area. After hemitransection the activity in the substantia nigra was decreased whereas in the ventral tegmental area it was unchanged. Our results thus suggest that dopaminergic cells in the ventral tegmental area do not receive GABAergic fibres from the terminal regions of the ascending dopaminergic fibres. In addition, we found a very high concentration of glutamate decarboxylase in a region traversed by the rostral medial forebrain bundle. Here the activity was mainly confined to the paniculate fraction, probably the synaptosomes. This fraction also displayed a very active high affinity uptake of y-aminobutyric acid.     

Distribution of arginine vasotocin in the brain of the lizard Anolis carolinensis

Summary The distribution of immunoreactive arginine vasotocin (AVT-ir) was determined in the brain of the lizard Anolis carolinensis. Cells and fibers containing AVT-ir were found in the medial septal region, lamina terminalis, lateral forebrain bundle, preoptic area, supraoptic nucleus, anterior hypothalamus, paraventricular nucleus, periventricular nucleus, arcuate nucleus, and ventromedial nucleus of the thalamus. Occasional AVT-ir cells were found in the interpeduncular nucleus. Fibers containing AVT-ir were found in the cortex, around the olfactory ventricle, in the diagonal band of Broca, amygdala area, dorsal ventricular ridge, striatum, nucleus accumbens, septum, ventromedial hypothalamus, lateral hypothalamus, medial forebrain bundle, median eminence, pars nervosa, nucleus of the solitary tract, locus coeruleus, cerebellar cortex (granular layer), dorsal part of the nucleus of the lateral lemniscus, substantia nigra, and myelencephalon. The intensity of AVT-ir staining was, in general, greater in males than in females. Comparison of AVT-ir distribution in A. carolinensis with those previously published for other reptilian species revealed species-specific differences in distribution of AVT.     

Electrophysiological investigation of cortico-hypothalamic relations in cats

Projections of different parts of the orbito-frontal cortex, the basal temporal cortex, and the hippocampus on hypothalamic nuclei were studied by recording focal responses in acute experiments on cats anesthetized with pentobarbital and chloralose. The proreal gyrus was shown to have local projections in the latero-dorsal zones of the preoptic region, in the rostral parts of the medial forebrain bundle, and also in the region of the lateral and posterior hypothalamus with the mammillary bodies. The orbital gyrus projects mainly to the latero-dorsal portions of the forebrain bundle, the latero-ventral part of the preoptic region, and the region of the lateral and latero-dorsal hypothalamic nuclei; projections from the orbital gyrus are relatively diffuse in character. The basal temporal cortex has diffuse projections in the central part of the preoptic region, in the latero-ventral parts of the medial forebrain bundle, and in the lateral mammillary body. No marked foci of activity were found in the hypothalamic structures during hippocampal stimulation. Diffuse projections of the hippocampus were traced in the ventral part of the preoptic region and the ventral regions of the medial forebrain bundle, and also in the lateral hypothalamus and in the lateral mammillary nucleus.A. M. Gor'kii Donetsk Medical Institute. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 358–365, July–August, 1976.     

Distribution of catecholaminergic and serotoninergic systems in forebrain and midbrain of the newt,Triturus alpestris (Urodela)

Summary Mapping of monoaminergic systems in the brain of the newt Triturus alpestris was achieved with antisera against (1) thyrosine hydroxylase (TH), (2) formaldehyde-conjugated dopamine (DA), and (3) formaldehyde-conjugated serotonin (5-HT). In the telencephalon, the striatum was densely innervated by a large number of 5-HT-, DA-and TH-immunoreactive (IR) fibers; IR fibers were more scattered in the amygdala, the medial and lateral forebrain bundles, and the anterior commissure. In the anterior and medial diencephalon, TH-IR perikarya contacting the cerebrospinal fluid (CSF-C perikarya) were located in the preoptic recess organ (PRO), the organum vasculosum laminae terminalis and the suprachiasmatic nucleus. Numerous TH-IR perikarya, not contacting the CSF, were present in the posterior preoptic nucleus and the ventral thalamus. At this level, DA-IR CSF-C neurons were only located in the PRO. In the posterior diencephalon, large populations of 5-HT-IR and DA-IR CSF-C perikarya were found in the paraventricular organ (PVO) and the nucleus infundibularis dorsalis (NID); the dorsal part of the NID additionally presented TH-IR CSF-C perikarya. Most regions of the diencephalon showed an intense monoaminergic innervation. In addition, numerous TH-IR, DA-IR and 5-HT-IR fibers, orginating from the anterior and posterior hypothalamic nuclei, extended ventrally and reached the median eminence and the pars intermedia of the pituitary gland. In the midbrain, TH-IR perikarya were located dorsally in the pretectal area. Ventrally, a large group of TH-IR cell bodies and some weakly stained DA-IR and 5-HT-IR neurons were observed in the posterior tuberculum. No dopaminergic system equivalent to the substantia nigra was revealed. The possible significance of the differences in the distribution of TH-IR and DA-IR neurons is discussed, with special reference to the CSF-C neurons.Abbreviations AM amygdala - CAnt commissura anterior - CH commissura hippocampi - CP commissura posterior - Ctm commissura tecti mesencephali - DH dorsal hypothalamus - DTh dorsal thalamus - FLM fasciculus longitudinalis medialis - Fsol fasciculus solitarius - H habenula - LFB lateral forebrain bundle - ME median eminence - MFB medial forebrain bundle - NID nucleus infundibularis dorsalis - nIP neuropil of nucleus interpeduncularis - NPOP nucleus preopticus posterior - NS nucleus septi - OVLT organum vasculosum laminae terminalis - PD pars distalis - Pdo dorsal pallium - PHi primordium hippocampi - PI pars intermedia - Pl lateral pallium - PN pars nervosa - PRO preoptic recess organ - Ptec pretectal area - PVO paraventricular organ - Ra nucleus raphe - Rm nucleus reticularis medius - SCO subcommisural organ - ST striatum; strm stria medullaris thalami - strt stria terminalis thalami - TM tegmentum mesencephali - TO tectum opticum - TP tuberculum posterius - trch tractus cortico-habenularis - trmp tractus mamillopeduncularis - VH ventral hypothalamus - Vm nucleus motorius nervi trigemini - VTh ventral thalamus - II optic nerve     

Distribution of trigeminothalamic and spinothalamic lamina I terminations in the cat

The distribution in the thalamus of terminal projections from lamina I neurons of the trigeminal, cervical, and lumbosacral dorsal horn was investigated with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) in the cat. Iontophoretic injections were guided by single- and multi-unit physiological recordings. The injections in particular cases were essentially restricted to lamina I, whereas in others they spread across laminae I–III or laminae I–V. The trigemino- and spinothalamic (TSTT) terminations were identified immunohistochemically. In all cases, regardless of the level of the injections, terminal fibers were consistently distributed in three main locations: the submedial nucleus; the ventral aspect of the basal ventral medial nucleus and ventral posterior nuclei; and, the dorsomedial aspect of the ventral posterior medial nucleus. The terminal fields in the submedial nucleus and the ventral aspect of the ventral posterior group were topographically organized. Terminations along the ventral aspect of the ventral posterior group extended posterolaterally into the caudal part of the posterior nucleus and anteromedially into the ventromedial part of the ventral lateral nucleus. In several cases with trigeminal lamina I injections, a terminal labeling patch was observed within the core of the ventral posterior medial nucleus. In cases with spinal lamina I injections, terminations were also consistently found in the lateral habenula, the parafascicular nucleus, and the nucleus reuniens. Isolated terminal fibers were occasionally seen in the zona incerta, the dorsomedial hypothalamus, and other locations. These anatomical observations extend prior studies of TSTT projections and identify lamina I projection targets that are important for nociceptive, thermoreceptive, and homeostatic processing in the cat. The findings are consistent with evidence from physiological (single-unit and antidromic mapping) and behavioral studies. The novel identification of spinal lamina I input to the lateral habenula could be significant for homeostatic behaviors.     

Subcortical projections of the visual cortex in the adult albino rat and during postnatal development

We have investigated the subcortical projections of the rat striate cortex by using the silver-degeneration method and the HRP-technique too. Cortical lesions were made in 60 young animals (1, 4, 5, 6, 7, 10 and 14 days old) and in 6 adult rats. The terminal regions of projection occurred only ipsilateral to the lesions. After passing the internal capsule the degenerating pathway divides into 2 bundles. In the dorsal thalamus one of them runs in caudal direction. The other bundle turns ventrally, reaches the cerebral peduncle and terminates in the pons. The first fibre bundle terminates in the following structures: Nc. reticularis thalami, Nc. lateralis thalami, Nc. lateralis posterior thalami, Corpus geniculatum laterale, pars dorsalis (Cgld), Corpus geniculatum laterale, pars ventralis (Cglv), Nc. praetectalis anterior et posterior and Colliculus superior. The fibers of the second bundle innervate the Nc. lateralis pontis. Fibers from this bundle terminate probably in the Cglv and in the Zona incerta too. By using the HRP-technique it could be demonstrated that the axons terminating in the Cgld originate in layer VI of the area 17. In contrast, the projection to Cglv, Nc. lateralis posterior, Colliculus superior and Nc. lateralis pontis originates from pyramidal cells in layer V. The development of the projection in young animals indicates: Like in adults rats, terminal degeneration is present in all subcortical projection regions at postnatal day (PD) 10. At PD 4-7 we can observe heavily degenerating axons but the terminal degeneration is different. It is remarkable in the "visual" part of the reticular nucleus and iln the Cgld (decreasing from inside to outside). Only a weak terminal degeneration is visible in the pretectal region and in the superior colliculus. At PD 1 the trajectory of degenerating fibres is clearly visible. Signs of terminal degeneration can only be found in the reticular nucleus. It is discussed whether the date of generation of the cortical neurons and the time of the differentiation of the cortical layers is of importance for the time of innervation of the subcortical projection fields. The question when the axons arrive at their terminal region and form there synaptic contacts has not yet been exactly answered. To solve this problem electronmicroscopic investigations are necessary.     

Central connections of the olfactory bulb in the weakly electric fish,Gnathonemus petersii

Summary We have investigated the central connections of the classical olfactory system in the weakly electric fish Gnathonemus petersii using HRP and cobalt labelling techniques. The olfactory bulb projects bilaterally via the medial and lateral olfactory tracts to restricted areas of the telencephalon, namely to its rostromedial, lateral and posterior medial parts. The most extensive telencephalic target is the posterior terminal field, which arcs around the lateral forebrain bundle at levels posterior to the anterior commissure. Projections to the contralateral hemisphere cross in the ventral telencephalon rostral to the anterior commissure and via the posterior dorsal part of the anterior commissure; endings are also present within the anterior commissure. Bilateral projections to the preoptic area, to the nucleus posterior tuberis and to an area in the thalamus are apparent. In all cases, contralateral projections are less extensive than those on the side ipsilateral to the injected bulb. A projection via the medial olfactory tract can be followed to the contralateral bulb. Following injections into the olfactory bulb, retrogradely labelled neurons are found in the contralateral bulb and in six telencephalic areas; they are also present in the periventricular diencephalon and in an area lateral to the nucleus posterior tuberis. The present results support the suggestion that a reduction in olfactory input to the telencephalon occurs together with increased telencephalic differentiation in actinopterygian fishes.     

Autoradiographic distribution of I-galanin binding sites in the rat central nervous system

Galanin (GAL) binding sites in coronal sections of the rat brain were demonstrated using autoradiographic methods. Scatchard analysis of ¹²⁵I-GAL binding to slide-mounted tissue sections revealed saturable binding to a single class of receptors with a Kd of approximately 0.2 nM. ¹²⁵I-GAL binding sites were demonstrated throughout the rat central nervous system. Dense binding was observed in the following areas: prefrontal cortex, the anterior nuclei of the olfactory bulb, several nuclei of the amygdaloid complex, the dorsal septal area, dorsal bed nucleus of the stria terminalis, the ventral pallidum, the internal medullary laminae of the thalamus, medial pretectal nucleus, nucleus of the medial optic tract, borderline area of the caudal spinal trigeminal nucleus adjacent to the spinal trigeminal tract, the substantia gelatinosa and the superficial layers of the dorsal spinal cord. Moderate binding was observed in the piriform, periamygdaloid, entorhinal, insular cortex and the subiculum, the nucleus accumbens, medial forebrain bundle, anterior hypothalamic, ventromedial, dorsal premamillary, lateral and periventricular thalamic nuclei, the subzona incerta, Forel's field H₁ and H₂, periventricular gray matter, medial and superficial gray strata of the superior colliculus, dorsal parts of the central gray, peripeduncular area, the interpeduncular nucleus, substantia nigra zona compacta, ventral tegmental area, the dorsal and ventral parabrachial and parvocellular reticular nuclei. The preponderance of GAL-binding in somatosensory as well as in limbic areas suggests a possible involvement of GAL in a variety of brain functions.     

THE PALM GYNOECIUM

The morphology, anatomy, and histology of the gynoecia at or close to anthesis are described for 20 genera of palms selected to represent different taxonomic alliances and to include major gynoecial types within the family. Palms may have 1–10 carpels, but most have three. Fifteen genera, including 14 coryphoid palms and the monotypic Nypa fruticans, are apocarpous and the remainder, approximately 190, are syncarpous. Fusion of carpels in some gynoecia begins in the base, in others in the styles. Pseudomonomerous pistils occur in several different alliances: the ovarian parts of two carpels are reduced but three usually equal and functional styles and stigmas are present. The carpel is often follicular in shape with the ventral suture open or, more frequently, partially or completely closed. The carpel may be stipitate or sessile and usually has a conduplicate laminar part. Most carpels are spirally and laterally inserted on the receptacle, but the carpel in some unicarpellate genera (e.g., Thrinax) appears terminal. Stipes, ovarian parts, styles, and stigmas vary in structure and development. Septal nectaries which differ in size, in the presence or absence of specialized canals, and in position, characterize all genera of some groups but only some genera of others. Diverse vascular configurations in the bases of gynoecia vary according to the extent of the floral axis, the development of carpellary stipes, and the connation of the carpels and their adnation to the tip of the floral axis. Four types of carpellary vascular systems are present in the genera described: (1) most palm carpels have three major traces consisting of a dorsal bundle and two ventral bundles, and they may also have up to four pairs of lateral bundles or occasionally more; (2) in certain cocosoid palms no ventral bundles can be distinguished, but a dorsal bundle, many parallel lateral bundles, and a row of immature ventral strands vascularize each carpel; (3) carpels of Phytelephas have a dorsal bundle, two pairs of major lateral bundles and about four pairs of shorter lateral bundles, with no identifiable ventral bundles; (4) carpels of Nypa have many dichotomously branched bundles but none that are recognizable as dorsal, ventral, or lateral strands. Additional peripheral bundles or systems may be present in each of the above types. Ovules are supplied by 1–15 bundles. These are derived either from the carpellary stele; from ventral bundles only; from ventral, lateral, and dorsal bundles; or from a combination of these origins. Certain areas of the gynoecia or certain parts of dorsal carpellary walls in some genera are much less mature at anthesis than surrounding tissues. Implications for floral biology and relationships within the palms and of palms to other groups are discussed.     

Distribution of somatostatinlike immunoreactivity in the brain of the little brown bat (Myotis lucifugus)

The distribution of somatostatinlike immunoreactive (SLI) perikarya, axons, and terminals was mapped in subcortical areas of the brain of the little brown bat, Myotis lucifugus, using light microscopic immunocytochemistry. A preponderance of immunoreactivity was localized in reticular, limbic, and hypothalamic areas including: 1) in the forebrain: the bed nucleus of the stria terminalis; lateral preoptic, dorsal, anterior, lateral and posterior hypothalamic areas; amygdaloid, periventricular, arcuate, supraoptic, suprachiasmatic, ventromedial, dorsomedial, paraventricular, lateral and medial mammillary, and lateral septal nuclei; the nucleus of the diagonal band of Broca and nucleus accumbens septi; 2) in the midbrain: the periaqueductal gray, interpeduncular, dorsal and ventral tegmental, pretectal, and Edinger-Westphal nuclei; and 3) in the hindbrain: the superior central and parabrachial nuclei, nucleus incertus, locus coeruleus, and nucleus reticularis gigantocellularis. Other areas containing SLI included the striatum (caudate nucleus and putamen), zona incerta, infundibulum, supramammillary and premammillary nuclei, medial and dorsal lateral geniculate nuclei, entopeduncular nucleus, lateral habenular nucleus, central medial thalamic nucleus, central tegmental field, linear and dorsal raphe nuclei, nucleus of Darkschewitsch, superior and inferior colliculi, nucleus ruber, substantia nigra, mesencephalic nucleus of V, inferior olivary nucleus, inferior central nucleus, nucleus prepositus, and deep cerebellar nuclei. While these results were similar in some respects to those previously reported in rodents, they also provided interesting contrasts.     

Distribution of gastrin-releasing peptide immunoreactivity in the brain of the collared dove (Streptopelia decaocto)

The distribution of immunoreactivity after applying an antibody against gastrin-releasing peptide (GRP) was studied in the brain of the collared dove (Streptopelia decaocto). In the forebrain GRP-immunoreactive (GRP-ir) cells were found in the hyperstriatum accessorium, medial and lateral parts of the neostriatum, corticoidea dorsolateralis and temporoparieto-occipitalis areas, hippocampus, pre- and parahippocampal areas and prepiriform cortex. In the brainstem, GRP-ir cells were restricted mainly to the substantia nigra and ventral tegmental nucleus. Areas with densely packed GRP-ir clusters of varicosities were the medial intermediate hyperstriatum ventrale and lateral septal nucleus; dense GRP-ir neuropil was found in the parolfactory lobe, and in the dorsal half of the intermediate and caudal archistriatum. The ventral lamina medullaris contained many GRP-ir fibers. Forebrain areas devoid of immunoreactivity were the basal nucleus, ectostriatum, rostral archistriatum, most of the paleostriatum augmentatum and the lateral bed nucleus of the stria terminalis. Moderate densities of GRP-ir elements were found in the other telencephalic areas and further in, among others, the preoptic and hypothalamic region, ventral area of Tsai, cerulean nuclei, parabrachial complex, dorsal glossopharyngeal and vagus motor nuclei and medial nuclei of the solitary complex. The observations are compared with data from the literature and the implications for the definition of specific centers within the avian brain are discussed, with emphasis on systems with a role in visceral and motivational functions and in learning.     

Light and electron microscopic studies on the medial forebrain bundle in the rat. ii. nerve terminals from the medial hypothalamus.

After the surgical interruption of connections between the medial and lateral hypothalamus of the rat axonal (transient) and nerve terminal degeneration was shown in the medial forebrain bundle (MFB) with light and electron microscopy. Following 1 mm long parasagittal cuts at various rostro-caudal levels the degeneration pattern within the MFB indicated a certain territoral arrangement of terminating fibres from the medial hypothalamus. After a parasagittal cut through the lateral retrochiasmatic area, degeneration was observed in the full length of the MFB. This suggests that a number of axons connect the medial and lateral hypothalamus through this area. With the aid of a parasagittal cut separating totally the medial and lateral hypothalamus, the degeneration of dendrites in the middle portion of the lateral hypothalamus was also revealed. These proved to derive from cells of the ventromedial nucleus.     

Neuronal pathways to the margin of the hypothalamic median eminence and to the pituitary stalk of the rat. I. A golgi and degeneration study.

The course and termination of nerve fibres approaching the median eminence from lateral direction were studied in Golgi specimens and by the axon-degeneration technique. Varicose nerve fibres could be traced from an area corresponding to the medial and superficial portion of the medial forebrain bundle. They run immediately underneath the free ventral surface of the hypothalamus. Parasagittal knife-cuts placed at various distances (0.5 to 1.4 mm) from the midline resulted in a large number of degenerated axon fragments along the margin of the median eminence, on both sides of the tuberoinfundibular sulcus. Scattered degenerated fragments were found in the lateral part of the palisade zone as well as in the pituitary stalk. No degeneration could be seen in the abo9ve mentioned areas if the cut was as far as 1.8 mm from the midline. Degenerated axon fragments appeared as soon as 5 hours following the lesion indicating that the time course of ultrastructural degenerative alterations is remarkably fast in this fibre system.     

Obesity-inducing amygdala lesions: examination of anterograde degeneration and retrograde transport

Small lesions centered in the posterodorsal region of the medial amygdala resulted in excessive weight gains in female rats. Unilateral lesions were nearly as effective as bilateral lesions in the first 48 h after surgery (+21 to +32 g). Assessment of lesion damage was done by both qualitative evaluation and by a quantitative grid-point counting method. The critical sites for weight gain were the intra-amygdaloid bed nucleus of the stria terminalis and the posterodorsal medial amygdaloid nucleus. Incidental damage to the overlying globus pallidus was negatively related to weight gain. The cupric silver method for demonstrating axonal degeneration was applied to brains with obesity-inducing lesions. A dense pattern of degenerating terminals was found in the lateral septum, amygdala, ventral striatum, and ventromedial hypothalamus. Degeneration in the paraventricular nucleus of the hypothalamus was scarce or absent. Small retrograde tracer injections made in either the intra-amygdaloid bed nucleus of the stria terminalis or in the posterodorsal medial amygdaloid nucleus labeled cells in the amygdala, lateral septum, and hypothalamus, reciprocating the anterograde projections from the amygdala to these areas. The data suggest that subdivisions of the posterodorsal amygdala participate in the regulation of feeding in a manner that is similar to the better-known role of this part of the brain in mediating reproductive behavior. Although topographical differences may exist within the amygdaloid and hypothalamic subdivisions regulating these two sexually dimorphic behaviors, the relays engaged by feeding-related connections and those related to reproduction are remarkably parallel.     

Distribution of trigeminothalamic and spinothalamic lamina I terminations in the cat

The distribution in the thalamus of terminal projections from lamina I neurons of the trigeminal, cervical, and lumbosacral dorsal horn was investigated with the anterograde tracer Phaseolus vulgaris leucoagglutinin (PHA-L) in the cat. Iontophoretic injections were guided by single- and multi-unit physiological recordings. The injections in particular cases were essentially restricted to lamina I, whereas in others they spread across laminae I-III or laminae I-V. The trigemino- and spinothalamic (TSTT) terminations were identified immunohistochemically. In all cases, regardless of the level of the injections, terminal fibers were consistently distributed in three main locations: the submedial nucleus; the ventral aspect of the basal ventral medial nucleus and ventral posterior nuclei; and, the dorsomedial aspect of the ventral posterior medial nucleus. The terminal fields in the submedial nucleus and the ventral aspect of the ventral posterior group were topographically organized. Terminations along the ventral aspect of the ventral posterior group extended posterolaterally into the caudal part of the posterior nucleus and anteromedially into the ventromedial part of the ventral lateral nucleus. In several cases with trigeminal lamina I injections, a terminal labeling patch was observed within the core of the ventral posterior medial nucleus. In cases with spinal lamina I injections, terminations were also consistently found in the lateral habenula, the parafascicular nucleus, and the nucleus reuniens. Isolated terminal fibers were occasionally seen in the zona incerta, the dorsomedial hypothalamus, and other locations. These anatomical observations extend prior studies of TSTT projections and identify lamina I projection targets that are important for nociceptive, thermoreceptive, and homeostatic processing in the cat. The findings are consistent with evidence from physiological (single-unit and antidromic mapping) and behavioral studies. The novel identification of spinal lamina I input to the lateral habenula could be significant for homeostatic behaviors.     

Modulation of cerebral acetylcholine metabolism by the dorsal diencephalic conduction system in the rat

We investigated the effects of interruption of the impulse flow in the habenulopeduncular pathways by local infusion of tetrodotoxin on the acetylcholine and choline content in selected dopamine rich regions in the forebrain and midbrain in rats. The tetrodotoxin infusion caused a marked increase in acetylcholine content in the medial frontal cortex, striatum and ventral tegmental area+interpeduncular nucleus, but not in the limbic area or the substantia nigra, whereas choline content was reduced only in both the striatum and ventral tegmental area+interpeduncular nucleus. There was an increase in 3,4-dihydroxyphenylacetic acid content in the striatum after the manipulation. These findings suggest that the dorsal diencephalic conduction system may be involved in the integration of the activity of cholinergic neurons in the forebrain and midbrain regions and striatal dopanine neurons may play a role in the modulation of cholinergic neurons.     

The area octavo-lateralis in Xenopus laevis

Summary Central projections of afferents from the lateral line nerves and from the individual branches of the VIIIth cranial nerve in Xenopus laevis and Xenopus mülleri were studied by the application of HRP to the cut end of the nerves.Upon entering the rhombencephalon, the lateral line afferents form a longitudinal fascicle of ascending and descending branches in the ventro-lateral part of the lateral line neuropile. The fascicle exhibits a topographic organization, that is not reflected in the terminal field of the side branches. The terminal field can be subdivided into a rostral, a medial and a caudal part, each of which shows specific branching and terminal pattern of the lateral line afferents. These different patterns within the terminal field are interpreted as the reflection of functional subdivisions of the lateral line area. The study did not reveal a simple topographic relationship between peripheral neuromasts and their central projections.Two nuclei of the alar plate with significant lateral line input were delineated: the lateral line nucleus (LLN) and the medial part of the anterior nucleus (AN). An additional cell group, the intermediate nucleus (IN), is a zone of lateral line and eighth nerve overlap, although such zones also exist within the ventral part of the LLN and the dorsal part of the caudal nucleus (CN). Six nuclei which receive significant VIIIth nerve input are recognized: the cerebellar nucleus (CbN), the lateral part of the anterior nucleus, the dorsal medullary nucleus (DMN), the lateral octavus nucleus (LON), the medial vestibular nucleus (MVN) and the caudal nucleus (CN).All inner ear organs have more than one projection field. All organs project to the dorsal part of the LON and the lateral part of the AN. Lagena, amphibian papilla and basilar papilla project to separate regions of the dorsal medullary nucleus (DMN). There is evidence for a topographic relation between the hair cells of the amphibian papilla (AP) and the central projections of AP fibers. The sacculus projects extensively to a region between the DMN and the LON. Fibers from the sacculus and the lagena project directly to the superior olive. Fibers from the utriculus and the three crista organs terminate predominantly in the medial vestibular nucleus (MVN) and in the adjacent parts of the reticular formation, and their terminal structures appear to be organotopically organised. Octavus fiber projections to the cerebellum and to the spinal cord are also described.     

Prevention of hypertension in the SH rat: effects of differential central catecholamine depletion.

Six-hydroxydopamine (6-OHDA) was administered intraventricularly to 6-week-old male spontaneously hypertensive (SH) rats of the Okomoto strain and to normotensive rats of the Kyoto-Wistar strain. In addition, bilateral lateral tegmental lesions were placed in 35-40-day-old SH rats to interrupt ascending noradrenergic pathways. SH rats treated with 6-OHDA did not develop hypertension and had lower heart rates than control rats. Blood pressure and heart rate of Kyoto-Wistar animals were unaffected by the drug treatment. 6-OHDA produced widespread depletion of norepinephrine throughout the CNS of both SH and Kyoto-Wistar rats. Bilateral lateral tegmental lesions interrupted the dorsal noradrenergic bundle and depleted forebrain norepinephrine. These lesions did not prevent the development of hypertension and led to an increased heart rate. It is concluded that 6-OHDA does not produce its effect through a nonspecific lowering of blood pressure, but rather, that it interferes with the expression of the hypertensive syndrome. The lack of effect seen following depletion of forebrain norepinephrine as the result of interruption of the dorsal noradrenergic bundle indicates that the fibers destroyed by this lesion are not essential for the development of genetically determined hypertension.