Quantitative comparison of the hominoid thalamus. I. Specific sensory relay nuclei.

Studies to date have indicated few differences in sensory perception among hominoids. Sensory relay nuclei in the dorsal thalamus--portions of the medial and lateral geniculate bodies (MGBp, LGBd) and the ventrobasal complex (VB)--in two gibbons, one gorilla, one chimpanzee and three humans were examined for anatomical similarity by measuring and estimating the nuclear volumes, neuronal densities, numbers of neurons per nucleus, and volumes of neuronal perikarya. The absolute volumes of these nuclei were larger in the larger brains; however, with the volume of the dorsal thalamus as a standard, these sensory relay nuclei showed negative allometry. The gibbons had about half as many neurons as did the other hominoids. Although the human VB had slightly more neurons, the numbers of neurons in LGBd and MGBp did not significantly differ between the great apes and humans. The volumetric distribution of the neuronal perikarya were similar among these hominoids. Other thalamic nuclei had much more diverse numbers of neurons and relative frequencies of their neuronal perikarya. The sensory relay nuclei appear to be a group of conservative nuclei in the forebrain. These results suggest that as a neurological base for complex behaviors evolved in hominids, not all parts of the brain changed equally.     

A quantitative comparison of the hominoid thalamus: II. Limbic nuclei anterior principalis and lateralis dorsalis

Structures in the limbic system are commonly thought to be similar in form and function in all mammalian brains. In the study reported here, two thalamic limbic nuclei, N. anterior principles and N. lateralis dorsalis, were compared among a group of extant of extant hominoids. The nuclear volumes, neuronal densities, number of neurons per nucleus, and volumes of neuronal perikarya were measured. Humans have much larger nuclei but the nuclei constitute a similar proportion of the whole thalamus as found in the other hominoids. Whereas the human limbic nuclei were observed to have a decrease in the densities of nerve cells compared with those of the other hominoids, this difference is less than that found in most other thalamic nuclei. Consequently the estimated number of neurons is much higher for humans. The total number of neurons best separates the human limbic nuclei from those of the other hominoids. This preliminary study suggests that during hominid evolution neurons were preferentially added to the limbic nuclei of the thalamus.     

Mapping the Effects of SI Cortex Stimulation on Somatosensory Relay Neurons in the Rat Thalamus: Direct Responses and Afferent Modulation

We have used single-unit recording techniques to map the spatial distribution of the primary somatosensory (SI) cortical influences on thalamic somatosensory relay nuclei in the rat. A total of 193 microelectrode penetrations were made to record single neurons in tracks through the medial and lateral ventroposterior (VPL and VPM), ventrolateral (VL), posterior (Po), and reticular (nRt) thalamic nuclei. Single units were classified according to their (1) location within the nuclei, (2) receptive fields, and (3) response to standardized microstimulation in deep layers of the SI cortical forepaw areas. The SI stimulation produced short-latency (1- to 7-msec) excitatory responses in different percentages of neurons recorded in the following thalamic nuclei: VPL, 42.0%; Po, 25.0%; nRt, 16.4%; VL, 13.6%; and VPM, 9.9%. Within the VPL, the highest proportion of responsive neurons was found in the anterior region. Although most of the VL region was unresponsive, the caudal subregion bordering the rostral VPL showed some responsiveness (13.6% of neurons). In general, the spatial pattern of corticothalamic influences appeared to reciprocate the known thalamocortical connection patterns, but with a heterogeneity that was unpredicted.

The same parameters of SI cortical stimulation were used in studies of corticofugal modulation of afferent transmission through the VPL thalamus. A condition—test (C-T) paradigm was implemented in which the cortical stimulation (C) was delivered at a range of time intervals before test (T) mechanical vibratory stimulation was applied to digit 4 of the contralateral forepaw. The time course of cortical effects was analyzed by measuring the averaged evoked unit responses of thalamic neurons to the T stimuli, and plotting them as a function of C-T intervals from 5 to 50 msec. Of the 20 VPL neurons tested during SI stimulation, the average response to T stimulation was decreased a mean of 36%, with the suppression peaking (at 49% inhibition of the afferent response) about 15 msec after the C stimulus. Considerable rostrocaudal variation was observed, however. Whereas neurons in the rostral VPL (near VL) were strongly inhibited (-69%), neurons in the middle and caudal VPL exhibited facilitations at long and short C-T intervals, respectively. This study establishes a specific projection system from the forepaw region of SI cortex to different subregions of the VPL thalamus, producing specific temporal patterns of sensory modulation.     

Mapping the effects of SI cortex stimulation on somatosensory relay neurons in the rat thalamus: direct responses and afferent modulation

We have used single-unit recording techniques to map the spatial distribution of the primary somatosensory (SI) cortical influences on thalamic somatosensory relay nuclei in the rat. A total of 193 microelectrode penetrations were made to record single neurons in tracks through the medial and lateral ventroposterior (VPL and VPM), ventrolateral (VL), posterior (Po), and reticular (nRt) thalamic nuclei. Single units were classified according to their (1) location within the nuclei, (2) receptive fields, and (3) response to standardized microstimulation in deep layers of the SI cortical forepaw areas. The SI stimulation produced short-latency (1- to 7-msec) excitatory responses in different percentages of neurons recorded in the following thalamic nuclei: VPL, 42.0%; Po, 25.0%; nRt, 16.4%; VL, 13.6%; and VPM, 9.9%. Within the VPL, the highest proportion of responsive neurons was found in the anterior region. Although most of the VL region was unresponsive, the caudal subregion bordering the rostral VPL showed some responsiveness (13.6% of neurons). In general, the spatial pattern of corticothalamic influences appeared to reciprocate the known thalamocortical connection patterns, but with a heterogeneity that was unpredicted. The same parameters of SI cortical stimulation were used in studies of corticofugal modulation of afferent transmission through the VPL thalamus. A condition-test (C-T) paradigm was implemented in which the cortical stimulation (C) was delivered at a range of time intervals before test (T) mechanical vibratory stimulation was applied to digit 4 of the contralateral forepaw. The time course of cortical effects was analyzed by measuring the averaged evoked unit responses of thalamic neurons to the T stimuli, and plotting them as a function of C-T intervals from 5 to 50 msec. Of the 20 VPL neurons tested during SI stimulation, the average response to T stimulation was decreased a mean of 36%, with the suppression peaking (at 49% inhibition of the afferent response) about 15 msec after the C stimulus. Considerable rostrocaudal variation was observed, however. Whereas neurons in the rostral VPL (near VL) were strongly inhibited (-69%), neurons in the middle and caudal VPL exhibited facilitations at long and short C-T intervals, respectively. This study establishes a specific projection system from the forepaw region of SI cortex to different subregions of the VPL thalamus, producing specific temporal patterns of sensory modulation.     

Somato-dendritic synapses in the nucleus reticularis thalami of the rat

In the reticular nucleus of the rat thalamus, about 30% of the synapses are brought about by the perikarya of parvalbumin-immunopositive neurons, which establish somato-dendritic synapses with large dendrites of nerve cells of specific thalamic nuclei. Although the parvalbumin-immunopositive presynaptic structures bear resemblance to goblet-like or calyciform axonal endings, electron microscopic immunocytochemistry and in situ hybridization revealed that these structures are parts of the perikaryal cytoplasm studded with synaptic vesicles. In about 15% of the somato-dendritic synapses, axons are seen to be in synaptic contact with the parvalbumin-immunoreactive perikaryon. Double immunohistochemical staining revealed that the parvalbumin immunoreactive presynaptic perikarya and dendrites contained GABA. It is assumed that the peculiar somato-dendritic synaptic complexes subserve the goal of filtration of impulses arriving at the reticular nucleus from various thalamic nuclei, thus processing them for further sampling.     

Afferent connections of the basolateral division of the amygdaloid complex of the cat brain

Injection of horseradish peroxidase into the basal macrocellular and lateral nuclei of the amygdaloid complex (BLAC) in the cat brain has revealed their rich thalamic afferentation. On the BLAC there are massive projections of: a) nuclei of the middle line of the precommissural pole of the dorsal thalamus (anterior parts of the paratenial, interanteromedial and reunial nuclei), as well as the whole anterior paraventricular nucleus, medial part of the ventral posteromedial nucleus; b) postcommissural nuclei of the dorsal thalamus; some "nonacustical" nuclei of the internal geniculate body (ventrolateral nucleus, medial and macrocellular parts and the most caudal end of the internal geniculate body). Rather essential are projections of the "posterior group nuclei", those of the suprageniculate nucleus, of some parts of the ventral thalamus (subparafascicular nucleus, marginal and peripeduncular nuclei) and parabrachial nucleus. Scattered single projections are obtained from all hypothalamic parts (most of all the ventromedial nucleus), reticular nuclei of the septum, substantia innominata, substantia nigra, truncal nuclei of the raphe. Variety of the dorsal thalamic nuclei, sending their fibers to the BLAC reflects variety of sensory information, that gets here, according to its modality, degree of its differentiation and integrity. A number of the dorsal thalamus nuclei, owing to abundance of labelled neurons, can be considered as special relay thalamic nuclei for the BLAC resembling corresponding relay nuclei for the new cortex.     

Ultrastructure of neurons in the ventromedial nucleus or the hypothalamus in ovariectomized rats with or without estrogen treatment

Summary The fine structure of the ventrolateral and dorsomedial subdivisions of the ventromedial nucleus (VMN) of the hypothalamus was examined in ovariectomized/control and ovariectomized/estrogen-treated rats to compare neurons of these areas to other neurons (specifically the ventrolateral thalamus), and to determine the effects of estrogen on these cells. The neurons of the VMN contain a large nucleus with a prominent nucleolus, rough endoplasmic reticulum (RER), polysomes, a Golgi complex, coated, uncoated and dense-cored vesicles, lysosome-like bodies, inclusion bodies, multivesicular bodies, whorl bodies and myelin figures. Similar organelles were present in the neurons of the ventrolateral thalamus, although polysomes were more prominent, and the cells lacked dense-cored vesicles in the perikarya. Differences in the cells of the VMN between ovariectomized/control and ovariectomized/estrogen-treated rats included a more conspicuous stacking of the RER and greater number of dense-cored vesicles in the estrogen-treated group in both the ventrolateral and dorsomedial subdivisions. In both areas the differences were statistically significant, although more marked in the ventrolateral subdivision. In both VMN subdivisions, the increased stacking of the RER could be correlated with the greater number of dense-cored vesicles and may reflect increased biosynthesis of a secretory product.Supported by grants from the National Institutes of Health (1 R01 NS15889-01) to R.S.C. and (HD-05751) to D.W.P.     

The trajectory of sensory pathways from the lamina terminalis to the insular and cingulate cortex: a neuroanatomical framework for the generation of thirst

The pathways involved in the emotional aspects of thirst, the arousal and affect associated with the generation of thirst and the motivation to obtain satiation, have been studied but remain poorly understood. Rats were therefore injected with the neurotropic virus pseudorabies in either the insular or cingulate cortex. After 2 days of infection, pseudorabies-positive neurons were identified within the thalamus and lamina terminalis. In a separate group of rats, the retrograde tracer cholera toxin subunit b (CTb) was used in combination with either isotonic (0.15 M NaCl) or hypertonic (0.8 M NaCl) saline (1 ml/100 g body wt ip). Rats injected with CTb in the insular cortex and stimulated with hypertonic saline had increased numbers of Fos/CTb double-positive neurons in the paraventricular, rhomboid, and reuniens thalamic nuclei, whereas those rats injected with CTb in the cingulate cortex and challenged with hypertonic saline had increased numbers of Fos/CTb double-positive neurons in the medial part of the mediodorsal, interanteromedial, anteromedial, and ventrolateral part of the laterodorsal thalamic nuclei. Rats injected with CTb in the dorsal midline of the thalamus and challenged with hypertonic saline had increased numbers of Fos/CTb double-positive neurons within the organum vasculosum of the lamina terminalis (OVLT), median preoptic nucleus, and insular cortex but not the subfornical organ. A small proportion of the CTb-positive neurons in the OVLT were immunopositive for transient receptor potential vanilloid 1, a putative osmoresponsive membrane protein. These results identify functional thalamocortical pathways involved in relaying osmotic signals to the insular and cingulate cortex and may provide a neuroanatomical framework for the emotional aspects of thirst.     

The neuronal organization of the dentate nucleus of the cerebellum

The intracellular activity of the neurons of the dentate nucleus was studied in cats anesthetized with Nembutal by means of their antidromic and synaptic excitation through stimulation of the red nucleus (RN) and the ventrolateral nucleus of the thalamus (VL), as well as the sensomotor cerebral cortex (CC) and the peripheral nerves of the posterior and anterior extremities. Several functionally delimited groups of neurons were isolated and studied. Efferent neurons, antidromically activated from nuclei of the brain stem, which did not react to stimulation of the peripheral nerves were placed in group I. Group II neurons were synaptically activated from the nuclei of the brain stem, and in a majority of cases also reacted to stimulation of the peripheral nerves and CC. Cells with a rhythmic background activity, which did not react to any of the types of stimulation used, comprised group III. Group IV was made up of neurons having the properties of intermediate neurons with a selective reaction to stimulation of a specific peripheral nerve or which experience broad convergence of the effects of different afferent impulsations.L. A. Orbeli Institute of Physiology, Academy of Sciences of the Armenian SSR, Erevan. Translated from Neirofiziologiya, Vol. 3, No. 2, pp. 154–165, March–April, 1971.     

Reorganization of the vestibular-thalamic projections following injury of the cerebellar interpositus and deiters vestibuar nuclei

Plastic reorganization of the vestibular-thalamic system was studied in adult cats. It was shown, that preliminary (3 months before) injury of the cerebellar contralateral nucleus interpositus or lateral vestibular nucleus of Deiters leads to reorganization of vestibular-thalamic projections. Ipsilateral projections to the ventrolateral nucleus of thalamus arised from vestibular nuclear complex since the pattern of normal representations to mentioned thalamic nucleus were changed. The peculiarities of distribution and morphological structure of vestibular neurons forming new projections to the ventrolateral thalamic nucleus were studied as well.     

Unit responses of the ventral posterior and ventral lateral thalamic nuclei to electrical stimulation of the thalamic reticular nucleus

A microelectrode investigation was made of responses of 72 physiologically identified neurons of the ventral posterior (VP) and 116 neurons of the ventral lateral (VL) thalamic nuclei to electrical stimulation of the reticular (R) thalamic nucleus. Mainly those neurons of VP and VL (73.7 and 86.2% respectively) which responded to stimulation of the first motor area and nucleus interpositus of the cerebellum responded to stimulation of R; 19.8% of VL neurons tested responded to stimulation of R by an antidromic action potential with latent period of 0.5–2.0 msec and 46.6% of neurons responded by orthodromic excitation; 23% of orthodromic responses had a latent period of 0.9–3.5 msec and 77% a latent period of 4.0–21.0 msec; 19.8% of VL neurons tested were inhibited. Among IPSPs recorded only one was monosynaptic (1.0 msec) and the rest polysynaptic. It is postulated that both R neurons are excitatory and that the inhibition which develops in VL neurons during stimulation of R are connected mainly with activation of inhibitory interneurons outside the reticular nucleus.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 9, No. 5, pp. 477–485, September–October, 1977.     

刺激兔丘脑不同核团和胼胝体引起的膈神经放电效应

实验在33例清醒、肌肉麻痹和切断双侧迷走神经的家兔上进行,观察了刺激丘脑不同核团(VIL,VL,VPM 和 MI)和胼胝体纤维以激活皮层时膈神经的放电效应。当在吸气相(膈神经放电时)给予上述核团及胼胝体纤维电脉冲刺激,可使膈神经放电短暂抑制,随后的呼气相缩短、吸气相提前出现。如果在呼气相刺激上述核团,也能使该呼气时相缩短,随后的吸气时相提前出现。当在皮层接受 VL 投射的局部区域给予回苏灵后,再刺激 VL,皮层诱发电位增大,除使原先的膈神经放电效应更为明显外,还可在呼气相刺激时引起膈神经即刻的短暂放电。以上实验结果提示,当用回苏灵使皮层活动加强后,刺激丘脑 VL 引起的膈神经放电效应明显增强。损毁红核或切断皮层下行传导束但保留皮层脊髓束后,刺激丘脑引起的膈神经放电效应均不受影响,表明传入冲动激活皮层后引起的膈神经放电效应可能主要经皮层脊髓束下传,而皮层红核脊髓束不起重要作用。     

Properties of thalamocortical cells identified by antidromic stimulation in the ventrolateral and ventrobasal thalamic nuclei in rats

The physiological and pharmacological properties of thalamocortical neurons, identified by electrical antidromic stimulation of the frontoparietal cortex, were studied in the ventrobasal and ventrolateral thalamic nuclei in urethane anaesthetized rats. The spontaneous activity and conduction velocity of these neurons were similar in both nuclei. At both sites, thalamocortical neurons could be excited through iontophoretic application of acetylcholine and muscarinic or nicotinic agonists. Despite the known differences in thalamic organization of the two species, these properties are quite similar to those described in cat by other authors.     

In Vivo Optogenetic Control of Striatal and Thalamic Neurons in Non-Human Primates

Electrical and pharmacological stimulation methods are commonly used to study neuronal brain circuits in vivo, but are problematic, because electrical stimulation has limited specificity, while pharmacological activation has low temporal resolution. A recently developed alternative to these methods is the use of optogenetic techniques, based on the expression of light sensitive channel proteins in neurons. While optogenetics have been applied in in vitro preparations and in in vivo studies in rodents, their use to study brain function in nonhuman primates has been limited to the cerebral cortex. Here, we characterize the effects of channelrhodopsin-2 (ChR2) transfection in subcortical areas, i.e., the putamen, the external globus pallidus (GPe) and the ventrolateral thalamus (VL) of rhesus monkeys. Lentiviral vectors containing the ChR2 sequence under control of the elongation factor 1α promoter (pLenti-EF1α -hChR2(H134R)-eYFP-WPRE, titer 10⁹ particles/ml) were deposited in GPe, putamen and VL. Four weeks later, a probe combining a conventional electrode and an optic fiber was introduced in the previously injected brain areas. We found light-evoked responses in 31.5% and 32.7% of all recorded neurons in the striatum and thalamus, respectively, but only in 2.5% of recorded GPe neurons. As expected, most responses were time-locked increases in firing, but decreases or mixed responses were also seen, presumably via ChR2-mediated activation of local inhibitory connections. Light and electron microscopic analyses revealed robust expression of ChR2 on the plasma membrane of cell somas, dendrites, spines and terminals in the striatum and VL. This study demonstrates that optogenetic experiments targeting the striatum and basal ganglia-related thalamic nuclei can be successfully achieved in monkeys. Our results indicate important differences of the type and magnitude of responses in each structure. Experimental conditions such as the vector used, the number and rate of injections, or the light stimulation conditions have to be optimized for each structure studied.     

6-OHDA毁损黑质致密部对大鼠PPN和VL神经元放电活动的影响

目的：观察6-羟多巴胺单侧毁损黑质致密部多巴胺神经元后,脚桥核（PPN）和丘脑腹外侧核（VL）神经元自发放电活动的变化,探讨帕金森病（PD）的发病机制。方法：应用玻璃微电极细胞外记录法,观察对照组和PD组PPN和VL神经元的放电频率和放电形式的变化。结果：对照组和PD组大鼠PPN放电频率分别为（8．31±0．62）Hz和（10．70±0．85）Hz,PD组放电频率明显高于对照组（P〈0．05）。和对照组相比,PD组PPN的不规则和爆发式放电神经元构成比例明显增多（P〈0．01）,同时规则放电频率增加（P〈0．01）。对照组和PD组大鼠VL的放电频率分别为（6．25±0．54）Hz和（5．67±0．46）Hz,两组间没有显著性差异。VL神经元放电形式表现为不规则和爆发式放电,两组间构成比也没有明显差异,但PD组爆发式神经元放电频率明显降低（P〈0．01）。结论：PD状态下,PPN神经元活动增强,PPN可能参与了PD的病理生理过程,VL神经元放电可能受PPN神经元投射的调节。     

Mesotocin and vasotocin in the brain of the lizard Gekko gecko

Summary The distribution of mesotocin and vasotocin was studied in the brain of the lizard Gekko gecko with antisera specific for either peptide. Both mesotocinergic and vasotocinergic perikarya are found in the paraventricular and supraoptic nuclei of the hypothalamus, whereas vasotocinergic neurons are exclusively present in the bed nucleus of the stria terminalis and in a cell group of the rhombencephalon. The distributional pattern of the mesotocinergic fibers corresponds closely to that of the vasotocinergic fibers. However, throughout the entire brain the mesotocinergic innervation is less dense than the vasotocinergic innervation. No sex differences are present in the mesotocinergic fiber system.Abbreviations acc nucleus accumbens - bst bed nucleus of the stria terminalis - bv blood vessel - dB diagonal band of Broca - dc dorsal cortex - dth dorsolateral thalamic nucleus - lc lateral cortex - me median eminence - oc optic chiasma - ot optic tract - pag periaqueductal grey - pvn paraventricular nucleus - rc rhombencephalic cell group - sep septum - son supraoptic nucleus - tect mesencephalic tectum - vth ventrolateral thalamus     

Aminergic control of neuronal firing rate in thalamic motor nuclei of the rat

The effects induced on neuronal firing by microiontophoretic application of the biological amines noradrenaline (NA) and 5-hydroxytryptamine (5-HT) were studied "in vivo" in ventral-anterior (VA) and ventrolateral (VL) thalamic motor nuclei of anaesthetized rats. In both nuclei the amines had a mostly depressive action on neuronal firing rate, the percentage of units responsive to NA application (88%) being higher than to 5-HT (72%). Short-lasting (less than 2 min) and long lasting (up to 20 min) inhibitory responses were recorded, the former mostly evoked by NA and the latter by 5-HT ejection. In some cases 5-HT application had no effect on the firing rate but modified the firing pattern. NA-evoked responses were significantly more intense in VL than in VA neurons. Short-lasting inhibitory responses similar to NA-induced effects were evoked by the alpha2 adrenergic receptor agonist clonidine and to a lesser extent by the beta adrenergic receptor agonist isoproterenol. Inhibitory responses to 5-HT were partially mimicked by application of the 5-HT(1A) receptor agonist 8-hydroxy-2(di-n-propylamino)tetralin (8-OH-DPAT) and of the 5-HT2 receptor agonist alpha-methyl-5-hydroxytryptamine (ALPHA-MET-5-HT). The latter evoked excitatory responses in some cases. Both 5-HT agonists were more effective on VA than on VL neurons. The effects evoked by agonists were at least partially blocked by respective antagonists. These results suggest that although both 5-HT and NA depress neuronal firing rate, their effects differ in time course and in the amount of inhibition; besides aminergic modulation is differently exerted on VA and VL.     

The thalamus in the motor system.

The ventrolateral (VL) and anterior (VA) are the main thalamic relay for cerebellar and pallidal efferents going to the motor cortex. Four aspects of the function of these nuclei are briefly considered. (1) It is well known that these thalamic structures are not a simple relay on the way to the motor cortex, but that they have a gating function for the cerebellar afferents. The gating mechanism is active during slow-wave sleep, with deafferentation and with the use of various anesthetics. Possibly, it might play a role in the central organization of movement. (2) The organization at the unitary level of the projections between VL and motor cortex is examined and their role in the command of motor synergies through the motor cortex is strongly suggested. (3). It appears that unitary activity of VL neurons is not only related to movement but also to postural changes associated with movement. (4) The sensory input to VL nucleus is briefly analyzed. The inefficacy of exteroceptive stimulation in awake animals, in contrast with the effect of the same stimulation in anesthetized preparations, is discussed.     

A fluorescence microscopic study of the distribution of monoamines in the hypothalamus of the cat

Three distinct groups of monoamine (MA)-containing nerve cell bodies have been visualized in the hypothalamus and preoptic area of the cat by means of the Falck-Hillarp fluorescence histochemical technique. First, numerous small-sized catecholamine (CA) type neurons were disclosed within the ventral half of the periventricular area in the supraoptic and middle hypothalamic regions. The round to oval neurons of this medio-ventral group were more especially abundant around the base of the third ventricle, within the arcuate and supraopticus diffusus nuclei. Numerous medium-sized CA perikarya identified as the dorsal group, were also mapped out in the dorsal and posterior hypothalamic areas. Finally, a small population of both CA and serotonin (5-hydroxytryptamine, 5-HT)-containing neurons was disclosed within the lateral area of the middle and mammillary hypothalamic regions. These multipolar or elongated neurons which compose the lateral group were lying either along the ventrolateral surface of the hypothalamus or around the ventrolateral aspect of the fornix. In addition to these three MA cell groups, a few cells displaying a fluorescence of the CA type were also visualized in the so-called “dorsal chiasmatic nucleus” after α-methyl-dopa treatment. High density of CA axon terminals were found, on the other hand, in the external layer of the median eminence, in the dorsomedial, paraventricular, supraoptic and suprachiasmatic nuclei, and also within nucleus interstitialis of stria terminalis. In the present study, however, it was not possible to identify with certainty any concentration of 5-HT axon terminals in the cat hypothalamus. Therefore, except for the lateral cell group which could be peculiar to the cat, the topographical distribution of MA nerve cell bodies and axon terminals in the hypothalamus of the cat appears similar to the morphological organization of the MA neuronal elements in the hypothalamus of the rat.     

Osteocalcin- and Osteopontin-Containing Neurons in the Rat Hind Brain

Immunohistochemistry for osteocalcin (OC) and osteopontin (OPN) was performed to know their distributions in the hind brain of adult rats. OC- and OPN-immunoreactivity (-ir) were detected in neuronal cell bodies, including perikarya and proximal dendrites and the neuropil. In the cranial nerve motor nuclei, numerous OC- and OPN-immunoreactive (-ir) neurons were detected. The neuropil in the cranial motor nuclei mostly showed strong OC- and OPN-staining intensity. The cranial nerve sensory nuclei and other relay and modulating structures in the lower brain stem also contained various numbers of OC- and OPN-ir neurons. The staining intensities in the neuropil were varied among these regions. In the cerebellar cortex, Purkinje cells and granule cells showed OPN-ir but not OC-ir. However, OC- and OPN-ir neurons were abundantly distributed throughout the cerebellar nuclei. The neuropil in the cerebellar nuclei showed moderate OC-ir and strong OPN-ir staining intensities. These findings indicate that the distribution patterns of OC- and OPN-ir neurons were similar in many structures within the hind brain. OC may play a role in modulating neuroprotective function of OPN.