Characteristics of memory and the functional organization of the hippocampo-reticulo-neocortical complex of the brain in the acute postoperative period

In tests on dogs, rabbits and rats, it has been established that in acute postoperative period, the time of memorizing of conditioned signals (light, tone and metronome) is reduced, the time of realization of conditioned reactions increases, the excitability and the bloodflow of the midbrain reticular formation and Mg-AtPhase activity of pons Varolii raise. In the hippocampus the excitability and local bloodflow lower and the activity of Ca-Mg-ATPhase is enhanced. In the frontal cortex these processes do not change. Functional interrelations of the brain structures in the acute postoperative period are characterized by the weakening of the activating influence of the reticular formation on the frontal cortex and an increase of its suppressive action on the dorsal hippocampus. It is suggested, that the discovered damages in the higher nervous activity are stipulated by the changes in neurochemical organization of the brain.     

Intramedullary projections of the rostral nucleus of the solitary tract in the rat: gustatory influences on autonomic output

The efferent connections of the rostral nucleus of the solitary tract (NTS) in the rat were studied by anterograde transport of Phaseolus vulgaris leucoagglutinin. Rostral to the injection site, fibers travel through the rostral parvocellular reticular formation and deflect medially or laterally around the motor trigeminal nucleus, giving off few terminals in these nuclei and terminate in the parabrachial nucleus. Moderate projections to the peritrigeminal zone, including the intertrigeminal nucleus and the dorsal subcoeruleus nucleus, were observed. Caudally to the injection site, dense innervations from the rostral nucleus of the solitary tract were detected in the parvocellular reticular formation ventral and caudal to the injection site and in the intermediate and ventral medullary reticular formation. The rostral central and ventral subdivisions of the NTS up to the level where the nucleus of the solitary tract abuts the fourth ventricle and the hypoglossal nucleus, receive moderate input from the rostral nucleus of the solitary tract. In general, the projections from the rostral nucleus of the solitary tract were bilateral with an ipsilateral predominance. The caudal part of the nucleus of the solitary tract, the dorsal motor nucleus of the vagus and the facial nucleus were not labeled. It is concluded that medullary rNTS projections participate in oral motor behavior and autonomic control of abdominal organs.     

Sources of cortical,hypothalamic and spinal serotonergic projections: Topical organization in the dorsal raphe nucleus

A study was made of retrograde axon transport of luminescent stains (primulin, fluoro-gold, fast blue, and nuclear yellow) from the spinal cord, the frontal cortex and lateral hypothalamus to various neuron groups of the periventricular gray matter of the midbrain and the dorsal tegmentum of the pons Varolii. Two large groups of serotonergic neurons are localized in the dorsomedial area of the dorsal raphe nucleus where projections to the thoracic segments of the spinal cord originate. Some of these neurons form divergent axon collaterals to the frontal cortex. Our data indicate that the antinociceptive effect of stimulating the "purely analgesic zone" of the midbrain periventricular gray matter may be due to direct involvement of the dorsal raphe nucleus in the descending control of impulsation induced by nociceptive stimulation at the spinal cord level. The neurotransmitter and neuromodulator role of separate cortical and hypothalamic projections of serotonin-containing neurons in the dorsal raphe nucleus is discussed.A. M. Gorky Medical Institute, Donetsk. A. A. Bogomolets Institute of Physiology, Ukrainian Academy of Sciences, Kiev. Translated from Neirofiziologiya, Vol. 24, No. 1, pp. 87–96, January–February, 1992.     

Ascending and descending efferent pathways of the midbrain reticular formation of the cat (radioautographic study)

By means of the anterograde axoplasmic transport technique for a mixture of labelled aminoacids (3H-leucine and 3H-proline), ascending and descending systems of the reticular formation fibers in the cat mesencephalon have been studied. Projections from the mesencephalon reticular formation (MRF) ascend to the subthalamus, lateral, dorsal and periventricular hypothalamus, to the periventricular nuclei of the midline and to the intralaminar nuclei of the thalamus. The descending pathways project to the grey substance surrounding the aqueduct of cerebrum, locus coeruleus, parabrachial region and reticular formation of the pons and medulla oblongata. The projections to the reticular nucleus of the thalamus, ventral nucleus of the external geniculate body and superior colliculi arise from the dorsal half of the MRF, and projections to the striatum, lateral reticular nucleus of the medulla oblongata--from its ventral half. Most of the structures are reciprocally connected with the MRF.     

Role of the reticular formation of the midbrain in the process of formation of background activity of cortex neurons

In strict experimental conditions the basic activity of optic-cortex neurons in the rabbit was depressed after transverse section at the level of the rostral part of the reticular formation of the midbrain. Electrolytic destruction or functional blockage of the midbrain reticular formation (nucleus reticularis tegmenti) produces a decrease in frequency and magnitude in the grouping indexes of the cortex-neuron pulses that manifest the activity in these conditions. Destruction of specific nuclei in the optic pathway (those of the lateral geniculate body and the corpora bigemina) made no substantial change in the nature of the cortex-neuron pulses. Comparison of the parameters of pulsation activity of the same cortex neurons, as recorded before and after functional exclusion of the midbrain reticular formation, revealed that the increase in grouping of these pulses after the reticular formation was blocked induced changes in the intervals between groups of pulses, while the frequency of pulses within the groups remained constant. On the basis of the data obtained we may assume that the midbrain reticular formation plays an important role in generation of the background activity of cortex neurons, being a triggering mechanism that sets off a group of pulses. Distribution of pulses within the group is apparently due to the activity of cortex mechanisms only.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No. 1, pp. 43–51, January–February, 1970.     

Distribution and ultrastructure of pyramidal tract endings in the cat rhombencephalon

The distribution and ultrastructure of terminals of corticofugal fibers in the cat rhombencephalon were investigated under the optical and electron microscopes at different periods (2–6 days) of experimental degeneration evoked by destruction of the sensomotor cortex. It was shown by the Fink–Heimer method that most degenerating fibers are distributed in the reticular nuclei of the pons and medulla. Massive degeneration of corticofugal fibers also was observed in the nuclei of the dorsal columns (nuclei of Goll and Burdach). Most of the degenerating (the "pale" type of degeneration) axo-dendritic and axo-somatic synapses in the gigantocellular reticular nucleus and the nucleus of Goll retained spherical vesicles. Small endings were found on the branches of the dendrites in which degenerative changes were of the "dark" type. The topography of the degenerating elements and axo-axonal synapses was studied in large areas of sections by the coordinate grid method. The dimensions of most degenerating axons in the gigantocellular reticular nucleus were greater (1.5 µ) than those of the degenerating axons (0.5 µ) in the nucleus of Goll. Most endings of pyramidal fibers and axo-axonal synapses are located in the central part of the nucleus of Goll at a depth of 0.5–1.2 mm from the brain surface. The results are discussed in connection with electrophysiological studies of the mechanisms of cortical control over unit activity of the reticular formation of the brain stem and nuclei of the dorsal columns.     

Efferent connections of the centrum medianum of the cat thalamus revealed by autoradiography

Efferent connections of the centrum medianum and parafascicular nucleus of the thalamus (CM-Pf complex) in cats were studied by the method of anterograde axonal transport of tritiated amino acids followed by autoradiography. Projections from CM-Pf ascend to nuclei of the ventral group and nonspecific nuclei of the thalamus, preoptic, dorsal, lateral, and posterior areas of the hypothalamus, and also into the subthalamic region. Descending pathways are formed only by neurons of the caudomedial part of CM-Pf. They project into the pretectal region, superior colliculus, reticular formation, locus coeruleus, region of the ramus communicans, and substantia grisea centralis of the mesencephalon and pons, and also into the nuclei raphe, magnocellular reticular area, and inferior olivary nucleus of the medulla. In agreement with previous observations it was found that the caudomedial part of CM-Pf does not send direct projections into the cortex and striatum.I. P. Pavlov Institute of Physiology, Academy of Sciences of the USSR, Leningrad. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 224–230, March–April, 1984.     

Daily Modifications of 3h-Naloxone Binding Sites in the Rat Brain: A Quantitative Autoradiographic Study

The endogenous opioid peptides, the opiate receptors and several related behaviours, like opioid-mediated analgesia, show daily variations in different animal species including rats. The attempt to correlate the daily rhythm of opiate receptors in the central nervous system (CNS) to opiate related rhythmic phenomena requires an experimental approach with a high anatomical resolution, as the opioid distribution is very heterogeneous. In this paper we present the study of daily variations of 3H-naloxone binding sites in the different regions of the adult male rat brain, performed by means of quantitative autoradiography. Five rats are sacrificed at each investigated time of the day (0200, 0600,1000,1400,1800 and 2200). The ligand is 3H-naloxone(4nM), the quantification is performed by means of densitometric procedures (image analyzer Tesak VDC 501, computer Digital PDP11,3H-microscale). The statistical analysis is performed according to the single Cosinor method and the one-way analysis of variance followed by the multiple range test of Duncan. We analysed 33 different regions of the rat CNS, and the daily variations of opiate receptors are regionally selective. A circadian rhythm is found in the anterior cingulate cortex, hippocampal cortex, periventricular, medial, ventral, reticular and posterior nuclei of the thalamus, rhomboid, gelatinosus and rheuniens nuclei, lateral hypothalamus, locus coeruleus, grey substance of the pons, reticular formation of medulla oblongata, inferior olivary complex, medial part of the nucleus of the solitary tract and nucleus of the spinal tract of the trigeminal nerve. An ultradian rhythm is found in the medial and lateral preoptic areas, in the medial hypothalamus, in the medial and in the lateral nuclei of habenula. No significant variations during 24 hr according to the Cosinor analysis are found in the dorsal and lateral cerebral cortex, striatum, globus pallidus, bed nucleus of the stria terminalis, septal nuclei, lateral nucleus of the thalamus, cochlear nuclei, nucleus of the solitary tract, lateral and caudal parts, dorsal motor nucleus of the vagal nerve, XII and IX nerve nuclei. The amplitude of the daily variations observed ranges from 10 to 40%. Our results demonstrate the high anatomical selectivity of the daily modifications of 3H-naloxone binding sites in the rat CNS. They also indicate that quantitative autoradiography is a suitable and sensitive technique for these studies.     

fMRI signal changes in response to forced expiratory loading in congenital central hypoventilation syndrome.

Congenital central hypoventilation syndrome (CCHS) patients show impaired ventilatory responses to CO2 and hypoxia and reduced drive to breathe during sleep but retain appropriate breathing patterns in response to volition or increased exercise. Breath-by-breath influences on heart rate are also deficient. Using functional magnetic resonance imaging techniques, we examined responses over the brain to voluntary forced expiratory loading, a task that CCHS patients can perform but that results in impaired rapid heart rate variation patterns normally associated with the loading challenge. Increased signals emerged in control (n = 14) over CCHS (n = 13; ventilator dependent during sleep but not waking) subjects in the cingulate and right parietal cortex, cerebellar cortex and fastigial nucleus, and basal ganglia, whereas anterior cerebellar cortical sites and deep nuclei, dorsal midbrain, and dorsal pons showed increased signals in the patient group. The dorsal and ventral medulla showed delayed responses in CCHS patients. Primary motor and sensory areas bordering the central sulcus showed comparable responses in both groups. The delayed responses in medullary sensory and output regions and the aberrant reactions in cerebellar and pontine sensorimotor coordination areas suggest that rapid cardiorespiratory integration deficits in CCHS may stem from defects in these sites. Additional autonomic and perceptual motor deficits may derive from cingulate and parietal cortex aberrations.     

Magnetic resonance imaging in rapid eye movement sleep behavior disorder: Diffusion tensor imaging and voxel-based morphometry

Economo observed in 1930 that many cases of lethargy begin with a severe insomnia and fever followed by a long-lasting hypersomnia. We confirmed this evidence in animal cases where chemical lesions of the preoptic region resulted in severe insomnia accompanied with fever. Moreover, a subsequent pharmacological inhibition of neuronal activity of the posterior ventrolateral hypothalamus caused transient hypersomnia in these insomniac animals. However, vigilance states of the experimental animals returned to normal after several weeks, suggesting that the irreversible Economo’s lethargy may be due to the damage of passing fibers in the ventral hypothalamus. Similarly, chemical lesions of neurons of the midbrain reticular formation did not induce coma nor hypersomnia, which is inconsistent with lesion studies reported by Lindsley et al. using electrolytic coagulation. This fact further supports the importance of passing fibers in the midbrain. In addition, Mauthner in 1890 observed hypersomnia and abnormal eye movements in lethargic patients infected by “nona”, suggesting the implication of the periaqueductal gray in the vicinity of the 3rd nerve. We confirmed this hypothesis: hypersomnia was accompanied by a significant increase in REM sleep after chemical inactivation of a small part of the ventrolateral periaqueductal gray and dorsal portion of the subjacent reticular formation. On the other hand, removal of the tele- and di-encephalon caused an irreversible coma and abolished the daily rhythm of REM. This state of sleep is also regulated by forebrain structures and internal clocks in the suprachiasmatic nucleus.

     

Distribution of choline acetyltransferase and acetylcholinesterase in the nervous system of the dog

Choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activity were determined in 23 selected parts of the dog CNS and 4 parts of the peripheral nervous system. Maximum ChAT activity was found in the caudate nucleus and the ventral roots of the spinal cord. High activity was also present in the thalamus, the pons, the cerebral cortex, the medulla oblongata, the ventral spinal horns and the sciatic nerve. The lowest activity was measured in the cerebellum, the dorsal cord roots and the spinal ganglia. Maximum AChE activity was found in the caudate nucleus and the cerebellum. Relatively high activity was also present in the thalamus, the pons, the medulla oblongata, the grey matter of the spinal cord and the spinal ganglia. The lowest AChE activity was measured in the ventral and dorsal spinal roots.     

Distribution of Neuropeptide Y-Immunoreactive Neurons in the Human Brainstem, Cerebellum, and Cortex During Development

1. Neuropeptide Y is found throughout the central nervous system where it appears to play a wide range of often poorly understood functions. In this study, the distribution of neuropeptide Y immunoreactive (NPY-ir) neurons in the brainstem, cerebellum, and cerebral cortex of human fetuses ranging in age from 11 gestational weeks to term was investigated by immunohistochemistry. 2. The NPY-ir cells were detected in the dorsal and ventral rostral midbrain and the interpeduncular nucleus by 21 weeks and 32 weeks of gestation, respectively. Although no positive cells were found in the pons, the NPY-ir fibers were detected there at 32 gestational weeks. 3. The vagal, hypoglossal, and olivary nuclei of the medulla oblongata contained immunoreactive cells by week 21 and the medullary reticular formation by week 25 of gestation. In most of these locations, both the number and size of neuropeptide Y positive cells were greater at birth and reached maximal values of 100-400 cells per 1 mm2 and 2-5 microm in diameter, respectively. 4. In the cerebellum, numerous NPY-ir horizontal and granule cells, as well as the cells within the dentate nucleus were observed as early as 21 weeks of gestation. 5. The NPY-ir cells were also detected in the developing cerebral cortex, with the earliest activity observed within the temporal cortex at 14 weeks of gestation. By week 21, positive cells appeared in the visual, frontal, sensory, and motor cortices. Most of these cells were bipolar or multipolar in morphology but their numbers at birth were relatively low. 6. Our results show a wide distribution of the NPY-ir cells in the developing human brain and offer supporting evidence for the important modulatory role of NPY in both the fetus and adult.     

Afferent connections of the dorsal magnocellularis area of the cat red nucleus

Location within the brain of retrogradely labeled neurons putting out projections from the dorsal magnocellularis area of the red nucleus was investigated by means of microiontophoretic injection of horseradish peroxidase into the dorsal magnocellularis area of the cat red nucleus. Projections were found from a number of hypothalamic nuclei, the centrum medianum, parafascicular and subthalamic nuclei, zone incerta, Forel's field, nucleus medialis habenulae, pontine and bulbar reticular formation, and the following midbrain structures: the central gray matter, superior colliculus, Cajal's interstitial nucleus, reticular formation, and the contralateral red nucleus. Projections were also identified proceeding from more caudally located structures: the cerebellar fastigial nucleus, facial nucleus, medial vestibular and dorsal lateral vestibular nuclei, and ventral horns of the spinal cord cervical segments. Connections between the substantia nigra and the red nucleus were clarified. Projections to the red nucleus from the cerebral cortex, interstitial and dentate (lateral) cerebellar nuclei, the nucleus gracilis and cuneate nucleus were found, confirming data presented in the literature. Bilateral trajectories of retrogradely labeled fiber systems are described.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 19, No. 6, pp. 810–816, November–December, 1987.     

An analysis of the neuronal processes in the activating brain systems of the rat during the acquisition of an instrumental defense reflex

In chronic experiment, a defensive conditioned reflex was elaborated in rats with electrodes implanted in the reticular oral pons nucleus, cortico-medial group of amygdalar nuclei, ventromedial hypothalamic nucleus and central grey substance of the midbrain. Synchronization of the activity of neuronal groups of emotiogenic formations in the studied brain structures, became enhanced at formation of the conditioned reflex. A dependence was revealed of the level of correlation of limbic neuronal groups activity on functional state of the reticular formation, as well as neurochemical correlation mechanisms. The increase (decrease) of coefficients of correlation of the activity of neuronal ensembles of limbic structures was accompanied by a change of evoked potentials parameters recorded in them.     

A crossed projection from the optic tectum to craniocervical premotor areas in the brainstem reticular formation. An anterograde and retrograde tracing study in the mallard (Anas platyrhynchos L.)

The optic tectum in birds receives visual information from the contralateral retina. This information is passed through to other brain areas via the deep layers of the optic tectum. In the present study the crossed tectobulbar pathway is described in detail. This pathway forms the connection between the optic tectum and the premotor area of craniocervical muscles in the contralateral paramedian reticular formation. It originates predominantly from neurons in the ventromedial part of stratum griseum centrale and to a lesser extent from stratum album centrale. The fibers leave the tectum as a horizontal fiber bundle, and cross the midline through the caudal radix oculomotorius and rostral nucleus oculomotorius. On the contralateral side fibers turn to ventral and descend caudally in the contralateral paramedian reticular formation to the level of the obex. Labeled terminals are found in the ipsilateral medial mesencephalic reticular formation lateral to the radix and motor nucleus of the oculomotor nerve, and in the contralateral paramedian reticular formation, along the descending tract. Neurons in the medial mesencephalic reticular formation in turn project to the paramedian reticular formation. Through the crossed tectobulbar pathway visual information can influence the activity of craniocervical muscles via reticular premotor neurons.     

A well defined spinocerebellar system in the weakly electric teleost fish Gnathonemus petersii. A tracing and immuno-histochemical study.

Long ascending fiber systems were investigated in the spinal cord of a teleost fish, Gnathonemus petersii. Concomitant results of Fink-Heimer degeneration tracing as well as CaBP28K immunohistochemical labelling demonstrate the existence of a well defined direct pathway from the very lowest spinal level to the caudal lobe of the cerebellum. HRP retrograde labelling shows that this pathway originates in a cellular column located in the most ventral part of the lateral column next to the lateral extremity of the ventral horn. From each spinal segment, the large axons of these cells gather and form a strip shaped tract at the periphery of the lateral column immediately dorsal to the cell column from which they originate. The spinal course of these fibers is ipsilateral; they give off a large number of collaterals to the lateral reticular nucleus. Bypassing the trigeminal motor nucleus, the lateral column tract courses dorsally to the paratrigeminal command associated nucleus between the lateral lemniscus and the nucleus preeminentialis and with a ventro-dorsally oriented large loop, turns in the caudal direction and penetrates into the cerebellar caudal lobe. Running caudally in the dorsal granular layer of the caudal lobe, it shifts more and more medially and crosses the midline whilst decussating with the contralateral tract on the dorsal margin of the molecular layer of the caudal lobe. Finally, the tract splits off and terminates throughout the granular layer of the caudal lobe. The main characteristics of this pathway are similar to those of the ventral spinocerebellar tract of higher vertebrates; it conveys information from all spinal levels directly to the contralateral cerebellum. However, it does not seem to receive direct synaptic input from the periphery, since projection of the dorsal root fibers appears to be limited to the dorsal ipsilateral half of the spinal cord. The appearance of such a pathway in a teleost fish is probably related to the existence of a well developed proprioceptive system in this species.     

大白鼠中缝核一氧化氮合酶阳性神经元的组织化学观察

中脑和脑桥部中缝核被认为与睡眠有直接和间接关系的重要脑结构。本文用一氧化氮合酶（ＮＯＳ）组织化学结合荧光组织化学方法证实在中缝核群中,ＮＯＳ阳性神经元主要定位于这两个脑部的中缝核内,ＮＯＳ产生的ＮＯ能使脑血管扩张,参与脑血流的调节。提示这二个脑部中缝核内的ＮＯＳ阳性神经元可能作为多种因素之一,参于睡眠状态下基本脑血流的维持     

Afferent connections to the abducent nucleus in the cat.

The afferent connections to the abducent nucleus in the cat were studied by means of retrograde transport of WGA-HRP after implantations of the tracer in crystalline form. Retrogradely labelled cells were found bilaterally in the medial and descending vestibular nuclei, mainly in their ventral and medial portions, in the rostral part of the ipsilateral gigantocellular reticular nucleus, in the medial part of the contralateral caudal pontine reticular nucleus and bilaterally in the oculomotor nucleus, mainly in its dorsolateral division. Some labelled cells were also found bilaterally in the mesencephalic reticular formation, the periaqueductal grey and the nucleus of the trapezoid body.