Immunohistochemical differentiation of electrophysiologically defined neuronal populations in the region of the rat hypothalamic paraventricular nucleus.

Intracellular recording and labeling were combined with neurophysin immunohistochemistry to study neurons in the paraventricular nucleus region of the rat hypothalamus. Neuronal membrane properties were examined in hypothalamic slices, and cells were labeled by injecting biocytin or Lucifer yellow. Slices were then embedded, sectioned, and immunohistochemically processed for neurophysin. Immunoreactivity patterns, and in some cases counterstaining, enabled determinations of the cytoarchitectonic positions of recorded cells to be made. Recorded cells were divided into three types according to their electrophysiological characteristics. The first type lacked low-threshold Ca2+ spikes and displayed linear current-voltage relations, a short time constant, and evidence for an A current. These were relatively large cells that were typically immunoreactive for neurophysin and were situated near other neurophysin-positive neurons. The second type had relatively small low-threshold potentials that did not generate bursts of Na+ spikes. These cells had heterogeneous current-voltage relations and intermediate time constants. They did not label for neurophysin, and most were located in the parvicellular subregion of the paraventricular nucleus. The third type had large low-threshold Ca2- spikes that generated bursts of Na+ spikes, and these cells had nonlinear current-voltage relations and long time constants. These neurons were dorsal or dorsolateral to the paraventricular nucleus and were not immunoreactive for neurophysin. These results indicate that paraventricular magnocellular neurons lack low-threshold potentials, whereas paraventricular parvicellular neurons display low-threshold potentials that generate one or two action potentials. Neurons that fire spike bursts from low-threshold potentials are adjacent to the paraventricular nucleus, confirming earlier reports.     

Comparison of the spatial distribution of seven types of neuroendocrine neurons in the rat paraventricular nucleus: Toward a global 3D model

The paraventricular nucleus of the hypothalamus (PVH) coordinates neuroendocrine, autonomic, and behavioral responses to help maintain energy and body water balance. The rat paraventricular nucleus has three major divisions: descending with axonal projections to somatomotor‐behavioral and autonomic circuitry, magnocellular neuroendocrine with projections directly to the posterior pituitary, and parvicellular neuroendocrine with projections to the median eminence for controlling anterior pituitary hormone secretion. The present work was undertaken to provide high‐resolution mapping of spatial relationships among the two magnocellular neuroendocrine and five parvicellular neuroendocrine neuron types throughout the nucleus. Double immunohistochemical labeling for two neuron types combined with retrograde labeling to identify neuroendocrine neurons positively was used in individual sections spaced 45 μm apart, along with a grid transfer method for reducing plane of section artifacts when comparing staining pattern data between animals. The results indicate that whereas each neuroendocrine neuron phenotype displays a unique distribution pattern, there is extensive partial overlap in a complex pattern between small “hot spots” with a relatively high density of a particular neuron type and few if any other phenotypes. In addition, the distribution of non‐neuroendocrine neurons staining with each of the markers (but not retrogradely labeled) was mapped and compared with each other and with the neuroendocrine neuron populations. This spatial organization raises important questions about the differential functional regulation of individual—and perhaps sets of—neuroendocrine motor neuron populations in the PVH by synaptic mechanisms and by less traditional mechanisms like dendritic neurotransmitter release and gap junctions within and between neuron types. J. Comp. Neurol. 516:423–441, 2009. © 2009 Wiley‐Liss, Inc.     

Effects of aging on the size,density, and number of rhesus monkey lateral geniculate neurons

Visual abilities decline during aging, and many of these declines are due to neural changes in the retina or brain. We have begun studies of the monkey visual system to investigate the location and nature of these changes as well as to answer general questions about the effects of aging on neural structure and function. We began with the dorsal lateral geniculate nucleus (LGN) because it is the main structure through which visual information passes on the way to cortex and because the parallel parvicellular and magnocellular pathways are most easily identified and studied in the LGN. In the present experiment, we determined the sizes, densities, and numbers of LGN neurons in young-adult (5 to 12.5 years) and old (23 to 27.5 years) rhesus monkeys. The measures were corrected for tissue shrinkage, and stereological procedures were used that yield unbiased estimates. In young-adult monkeys, neuron densities were lower in the magnocellular layers (about 14,000/mm³) than in the parvicellular layers (23,000/mm³). Neuron density increased about 28% from anterior to posterior in both types of layers. There was an average of approximately 1,267,000 neurons in the parvicellular layers and 148,000 neurons in the magnocellular layers; however, there was substantial variability (1.9-fold) among five brains studied. Aging produced a statistically significant decrease in neuron density in both the magnocellular (29% average decrease) and parvicellular (41% average decrease) layers. However, there was no significant loss of neurons. Rather, the density decrease was due to a small (nonsignificant) decrease in the number of neurons combined with a small (nonsignificant) increase in LGN volume. The increase in LGN volume was due to a significant increase in neuron soma-size and proportional increases in the volume of glial cells, blood vessels, and neuropil. These results, together with those of other studies, suggest that the effects of aging on the primate visual pathway from retina through striate cortex are relatively subtle. It is possible that the major neural changes occur more centrally. Alternatively, individual differences in the effects of aging may require much larger samples or prior screening to observe consistent changes. © 1993 Wiley-Liss, Inc.     

Regulation of cardiac sympathetic afferent reflex by GABA(A) and GABA(B) receptors in paraventricular nucleus in rats

The aim of the present study was to determine the role of GABA_A and GABA_B receptors in paraventricular nucleus (PVN) in regulating cardiac sympathetic afferent reflex (CSAR). Under urethane (800 mg/kg) and α-chloralose (40 mg/kg) anesthesia, renal sympathetic nerve activity (RSNA), mean arterial pressure (MAP) and heart rate (HR) were recorded in sinoaortic-denervated and cervical-vagotomized rats. CSAR was evaluated based in the response of RSNA to epicardial application of capsaicin (0.3 nmol) or bradykinin (1 nmol). Bilateral PVN microinjection of the GABA_A receptor agonist isoguvacine (10 nmol) attenuated CSAR, while the GABA_B receptor agonist baclofen (1 nmol) abolished CSAR. Both isoguvacine and baclofen greatly decreased baseline RSNA and MAP. The GABA_A receptor antagonist gabazine (0.1 nmol) had no significant effect on CSAR, but the GABA_B receptor antagonist CGP-35348 (10 nmol) enhanced CSAR. Gabazine caused greater increases in baseline RSNA and MAP than CGP-35348. Vigabatrin (10 nmol), a selective GABA-transaminase inhibitor which increases endogenous GABA level, abolished CSAR, and decreased baseline RSNA, MAP and HR. The effects of vigabatrin were antagonized by combined gabazine (0.1 nmol) and CGP-35348 (10 nmol). The results indicate that activation of either GABA_A or GABA_B receptors in the PVN inhibits CSAR, while blockage of GABA_B receptors in the PVN enhances CSAR. Endogenous GABA in the PVN could have an important role in regulating CSAR.     

A Golgi analysis of the primate globus pallidus. I. Inconstant processes of large neurons, other neuronal types, and afferent axons

The present paper is a Golgi study, with high-power lenses, of the primate globus pallidus. Two kinds of inconstant processes of large neurons are first described: complex endings and thin processes. Complex endings are thick apparatuses terminally located on dendrites having many appendages of various types. Contacts were observed not only between striatal axons and these complex endings but also between complex endings and the soma, dendritic stems, dendritic portions or complex endings of other large pallidal neurons. Thin processes were usually beaded, very thin, and arose from any part of the dendritic tree. Contacts were seen between them and soma or dendrites of other large neurons. These thin processes were very similar to initial axonal collaterals and together constitute a common pool of processes. Complex endings and thin processes were essentially observed in the lateral nucleus of the pallidum where they apparently are evenly distributed inside the nucleus but randomly distributed on individual neurons. Two neuronal types other than large pallidal neurons were isolated: the smallest were considered to be local circuit neurons, while intermediate-sized neurons might be the origin of a particular efference. Many striatal axons gave no branches over long distances and collaterals were of two types and most frequently were short (less than 50 micron). Larger axonal arborization were rarely encountered. In addition to parallel contacts, numerous very short ones were observed. All these contacts between striatal axons and dendrites of large pallidal neurons seem to be irregularly distributed.     

Hypothalamic and brainstem sources of pituitary adenylate cyclase-activating polypeptide nerve fibers innervating the hypothalamic paraventricular nucleus in the rat

The hypothalamic paraventricular nucleus (PVN) coordinates major neuroendocrine and behavioral mechanisms, particularly responses to homeostatic challenges. Parvocellular and magnocellular PVN neurons are richly innervated by pituitary adenylate cyclase-activating polypeptide (PACAP) axons. Our recent functional observations have also suggested that PACAP may be an excitatory neuropeptide at the level of the PVN. Nevertheless, the exact localization of PACAP-producing neurons that project to the PVN is not understood. The present study examined the specific contribution of various brain areas sending PACAP innervation to the rat PVN by using iontophoretic microinjections of the retrograde neuroanatomical tracer cholera toxin B subunit (CTb). Retrograde transport was evaluated from hypothalamic and brainstem sections by using multiple labeling immunofluorescence for CTb and PACAP. PACAP-containing cell groups were found to be retrogradely labeled from the PVN in the median preoptic nucleus; preoptic and lateral hypothalamic areas; arcuate, dorsomedial, ventromedial, and supramammillary nuclei; ventrolateral midbrain periaqueductal gray; rostral and midlevel ventrolateral medulla, including the C1 catecholamine cell group; nucleus of the solitary tract; and dorsal motor nucleus of vagus. Minor PACAP projections with scattered double-labeled neurons originated from the parabrachial nucleus, pericoeruleus area, and caudal regions of the nucleus of the solitary tract and ventrolateral medulla. These observations indicate a multisite origin of PACAP innervation to the PVN and provide a strong chemical neuroanatomical foundation for interaction between PACAP and its potential target neurons in the PVN, such as parvocellular CRH neurons, controlling physiologic responses to stressful challenges and other neuroendocrine or preautonomic PVN neurons.     

Medial preoptic and hypothalamic neuronal activity during sexual behavior of the male monkey

Neuronal activity changes in the medial preoptic area of the male monkey were related to the commencement of sexual behavior, penile erection and the refractory period following ejaculation.Increased neuronal activity in the dorsomedial hypothalamic nucleus was found to be synchronized to each mating act.The involvement of medial preoptic neurons in sexual arousal, initial penile erection and that of dorsomedial hypothalamic neurons in the copulatory act are suggested by the present findings.     

Functional and anatomic differentiation between parvicellular and magnocellular regions of red nucleus in the monkey

Single unit recording in awake monkeys was used to search for functional differences between the two divisions of the red nucleus, and anatomical tracing of WGA-HRP was used to investigate inputs to the two divisions. We studied a total of 323 units in 4 red nuclei of two monkeys. Recording sites were identified in histological sections by the locations of lesions and the reconstruction of electrode tracks. Of the units in the RNm 98.5% discharged in high frequency bursts during movement. Only 52% showed reliable responses to somatosensory stimulation, and the responses observed were weaker than the movement-related discharge. None of the units recorded in the RNp showed strong movement-related discharge, and 51% were completely unresponsive during both motor and sensory tests. A dorsolateral group of medium-sized cells that overlaps the rostral half of the main RNm and the caudal pole of RNp appears to represent an extension of the magnocellular region. Retrograde transport of WGA-HRP indicated that some of these cells are rubrospinal neurons. Furthermore, the discharge properties of dorsolateral neurons are like the main RNm neurons, except for lower discharge rates and smaller spike amplitudes. Mouth movements are strongly represented in the dorsolateral region. Anterograde transport of WGA-HRP from the motor cortex demonstrated dense terminal label in RNp as contrasted with light label in RNm. Retrograde transport of WGA-HRP from RNm labeled many more cells in the cerebellar interpositus nucleus than in motor cortex. We concluded that input to RNm from the cerebellum is the likely source of the strong movement-related activity recorded from cells in the RNm. The absence of appreciable movement-related activity in parvicellular red nucleus provides a clear functional distinction between this division and the magnocellular division of the red nucleus.     

Juxtacapsular nucleus of the stria terminalis of the adult rat: extrinsic inputs, cell types, and neuronal modules: a combined Golgi and electron microscopic study

This study unravels the microscopic organization of the juxtacapsular nucleus of the bed nuclei of the stria terminalis (Ju) by using silver impregnation and electron microscopic techniques. Examination of Golgi-impregnated specimens demonstrates that the Ju has precise boundaries primarily determined by a conical condensation of fibers of the stria terminalis (StT) around the nucleus. The internal capsule, ansa peduncularis, and medial forebrain bundle together with the StT provide extrinsic afferents to the neuropil of the Ju. Two main neuron types are found in the Ju: interneurons (including basket and neurogliaform cells) and projection neurons (bipolar and small pyramidal cells). The bipolar cell type accounts for about 80% of the sampled neurons. Short-axon neurons located within the dorsal part of the Ju send descending fibers that appear to terminate on the bipolar neurons, suggesting the existence of vertically oriented functional units within the nucleus. With the electron microscope, Ju neurons are seen in clusters of two or three neurons coupled by gap junctions. The neuropil contains numerous dendrites, axons, myelinated axons, and several types of synaptic interactions, including axospinous, axoshaft, and axosomatic. Within the neuropil, Ju neurons appear to be presynaptically modulated by axoaxonal interactions. The present findings suggest a model wherein bipolar neurons represent the output system of the Ju controlled by the interneurons, which would, in turn, be modulated by collaterals arising from the tributary fiber tracts. Additional neural interaction between Ju neurons utilizes gap junction-mediated electrotonic coupling.     

Comparison of photoreceptor spatial density and ganglion cell morphology in the retina of human,macaque monkey,cat, and the marmoset Callithrix jacchus

We studied the relationship between the morphology of ganglion cells and the spatial density of photoreceptors in the retina of two Old World primates, human and macaque monkey; the diurnal New World marmoset Callithrix jacchus; and the cat. Ganglion cells in macaque and marmoset were labelled by intracellular injection with Neurobiotin or by Dil diffusion labelling in fixed tissue. Cone photoreceptor densities were measured from the same retinas. Supplemental data for macaque and data for human and cat were taken from published studies. For the primates studied, the central retina is characterised by a constant numerical convergence of cones to ganglion cells. Midget ganglion cells derive their input, via a midget bipolar cell, from a single cone. Parasol cells derive their input, via a midget bipolar cell, from a single cone. Parasol cells derive their input from 40–140 cones. Outside the central retina, the convergence increases with eccentricity. The convergence to beta cells in the cat retina is very close to that for parasol cells in primate retina. The convergence of rod photoreceptors to ganglion cells is similar in human, macaque, and marmoset, with parasol cells receiving input from 10–15 times more rods than midget cells. The low convergence of cones to midget cells in human and macaque retinas is associated with distinctive “clusters” in midget cells' dendritic fields. Convergence in marmoset is higher, and the clusters are absent. We conclude that the complementary changes in photoreceptor density and ganglion cell morphology should be considered when forming linking hypotheses between dendritic field, receptive field, and psychophysical properties of primate vision. © 1996 Wiley-Liss, Inc.     

A Golgi study of the human neostriatum: neurons and afferent fibers

The neostriatum of 20 adult humans was examined in Golgi-Kopsch and rapid Golgi preparations. At least five types of neurons and four types of afferent fibers are described. Neurons of medium size with spine-rich dendrites (spiny type I) are the most frequent type. These cells exhibit a greater morphological diversity than those previously studied in the monkey. Also, quantitative data show that, compared to the monkey, spiny type I neurons in man have a greater somal size and dendritic field radius. Although the types of spines are similar, the mean density and radial distribution of spines along dendrites differ in the two species. Morphologic features of the axon, which is usually long with extensive collateral branches, suggest that more than one process from the axon may be efferent. Medium to large neurons with sparsely spined dendrites (spiny type II) differ from type I neurons in having a poorer branching and greater radial spread of their dendrites and a lower density of spines. They also differ from spiny type I neurons in their distribution and relative proportion of various spine types. The axon of the spiny type II neuron is long and has collaterals which are poorly arborized in comparison to those of spiny type I cells. Aspiny neurons are of medium (aspiny type I) and large (aspiny type II) size. They have varicose, curved dendrites and a short axon which arborizes mostly within the dendritic field. A group of smaller neurons with more variable dendritic morphology is also seen. Observations suggest that in the human brain the proportion of medium-sized aspiny neurons and small neurons may be greater than in other species.     

Morphology of retinal ganglion cells in a New World monkey,the marmoset Callithrix jacchus

We studied the morphology of retinal ganglion cells in a diurnal New World primate, the marmoset Callithrix jacchus. This species is of interest as a model for primate vision because it has good behavioural visual acuity, and the retina and subcortical visual pathways are very similar to those of Old World monkeys and humans. Ganglion cells were labelled by placing small crystals of the carbocyanin dye Dil into the optic fibre layer, or by intracellular injection of neurobiotin. Two main classes of ganglion cell were labelled. We call these Group A cells and Group B cells: they are respectively homologous to parasol and midget cell classes. Group A and Group B cells show similar patterns of dye coupling, dendritic stratification and dendritic field size as their counterparts in Old World monkeys and humans. A third group of cells, which we call Group C, is morphologically heterogeneous. Examples corresponding to wide-field ganglion cell types described in Old World primates were encountered. One subgroup of C cells has a morphology very similar to that of the small bistratified (blue-on) cell described in macaque retina, suggesting that this functional pathway is common to all primates. As for other New World monkeys, the marmoset shows a sex-linked polymorphism of cone pigment expression, such that all males are dichromats and the majority of females are trichromats. No systematic differences in Group B cells were seen between male and female retinas, suggesting that trichromacy is not accompanied by specific changes in ganglion cell morphology. © 1996 Wiley-Liss, Inc.     

GABA(B) receptor-activation inhibits GABAergic synaptic transmission in parvocellular neurones of rat hypothalamic paraventricular nucleus

The paraventricular nucleus of the hypothalamus contains three classes of neurones: (i) magnocellular and (ii) parvocellular neurosecretory neurones and (iii) nonendocrine projection neurones. The present study aimed to determine whether functional GABA(B) receptors are present on axon terminals that synapse with parvocellular neurosecretory and nonendocrine paraventricular neurones and to determine how activation of GABA(B) receptors control GABAergic input to these neurones. Whole-cell recordings were performed in coronal hypothalamic slices of the rat containing the paraventricular nucleus. GABA(A) receptor-mediated inhibitory postsynaptic currents (i.p.s.c.) were isolated pharmacologically in the presence of antagonists of glutamatergic ionotropic receptors. We found that baclofen, an agonist of GABA(B) receptors, decreased the frequency of spontaneous and miniature i.p.s.c. It also decreased the amplitude of evoked i.p.s.c. These effects were suppressed by CGP55845A, a competitive antagonist of GABA(B) receptors. CGP55845A also increased the frequency of miniature i.p.s.c. and the amplitude of evoked i.p.s.c., suggesting that, in physiological conditions, presynaptic GABA(B) receptors exert a tonic inhibition on GABA release. Baclofen had no effect on GABA-evoked postsynaptic currents, suggesting that the baclofen-dependent suppression of GABAergic i.p.s.c. was exclusively due to a presynaptic action of the agonist. Our data indicate that GABA(B) receptors are present on axon terminals of GABAergic presynaptic neurones contacting parvocellular neurosecretory and nonendocrine paraventricular neurones, and suggest that GABA(B) receptors exert a tonic inhibition of GABA release from GABAergic terminals. Activation of these receptors causes disinhibition of parvocellular neurosecretory and nonendocrine paraventricular neurones.     

Morphological study of the rostral interstitial nucleus of the medial longitudinal fasciculus in the monkey,Macaca mulatta by Nissl,Golgi, and computer reconstruction and rotation methods

We have studied the morphology of silver-impregnated neurons (rapid Golgi technique) in the rostral interstitial nucleus of the medial longitudinal fasciculus (riMLF), a center involved in the control of vertical and torsional saccadic eye movements. This morphological study of riMLF neurons in the rhesus monkey was undertaken to further our understanding of the functional circuitry of the oculomotor system. Our study employed Nissl, Golgi, and computer- assisted methods. The cytoarchitectonic boundaries of the riMLF and its relationships to neighboring structures were determined in both Nissl and Golgi preparations. Five (I–V) distinct morphological types of riMLF neurons were distinguished in the Golgi impregnations on the basis of soma size, dendritic size, numbers of primary dendrites, number of dendritic branch points, as well as form, number, and distribution of dendritic appendages. Type I neurons impregnated most frequently and had the most extensive and highly branched dendritic tree. Type II neurons displayed thick dendrites with complex dendritic appendages, but the dendritic tree was much more compact than that of type I cells. Type III and type V cells had fusiform somas and relatively unbranched dendritic trees but differed greatly in size as well as dendritic morphology. The type IV cell was the smallest neuron and had many characteristics of the local interneurons found in other thalamic, subthalamic, hypothalamic, and midbrain centers. The type V was the largest neuron, least frequently impregnated, and found only at rostral riMLF levels. Digitized reconstructions of each type of neuron were rotated by the computer, which revealed that the dendritic trees of types I, III, and V occupy a disk-like compartment in the riMLF neuropil. In contrast, the trees of types II and IV occupy a roughly spherical compartment. We suggest that three of the cell types are well suited for specific purposes: type II cells for receiving, topographically organized inputs that contain spatial information, type I cells for short-lead burst neuron output to the motor neurons or other premotor centers, and type IV cells for inhibitory inputs to type I cells. © 1994 Wiley-Liss, Inc.     

Modulation of neuronal activity by reward identity in the monkey subthalamic nucleus

The subthalamic nucleus (STN) has been argued to be an important component of reward‐sensitive basal ganglia circuitry. This view is especially supported by the behavioral changes observed after STN inactivation, which could reflect impairments in the motivational control of action. However, it is still unclear how the STN integrates reward information and to what extent such integration correlates with behavior. In this study, the response properties of STN neurons in monkeys performing reaching movements with a cue predicting the identity of an upcoming liquid reward (juice or water) were investigated. Although the timing of movements reliably indicated that monkeys had greater motivation for juice than water, rarely did task‐related changes in neuronal activity depend on the nature of the expected reward. Conversely, when presented with a choice of selecting a response that leads to juice or water delivery, animals showed a clear preference for juice and more than half of the neurons were differentially modulated dependent on the reward obtained, mostly after the monkeys's overt choice of action. Under such circumstances, an increase in activity specifically followed the action outcomes across the population of neurons when monkeys failed to choose the juice reward. These results indicate that STN neurons encode whether or not a preferred reward had been received when a choice between response alternatives is required. This differential neuronal activity might reflect the participation of the STN in evaluating the reward value of chosen actions, thus highlighting its contribution to decision‐making processes.     

Topography of the afferent connectivity of area 17 in the macaque monkey: a double-labelling study

The various structures afferent to area 17 (or V1) of the macaque monkey have widely differing retinotopic organizations. It is likely that these differences are reflected in the topographic organizations of the projections from these structures to area V1. We have investigated this issue by placing side-by-side injections of two retrograde fluorescent tracers, fast blue and diamidino yellow, in V1. By examining the extent of mixing of the two populations of singly labelled cells and the presence of doubly labelled cells, in different structures, we have characterized the topography of each projection in terms of the size of its axonal arborization and the amount of convergence and divergence. The afferents from the lateral geniculate nucleus (LGN) and from the pulvinar are organized in a point-to-point fashion. The maximum extent of axonal arborization of these afferents is 0.5 mm and these projections demonstrate little scatter (i.e., neighboring LGN neurons project to adjacent regions of V1). The other two subcortical structures examined, the claustrum and the intralaminar nuclei, demonstrate a much larger scatter and wider axonal arborizations in their projections to V1 than do the LGN and pulvinar. Two-dimensional reconstructions were made of the distribution of labelled neurons in extrastriate cortical areas. Using the separation between patches of labelled cells and transitions in myelin-stained sections, we have identified seven separate cortical regions containing labelled cells. Two of these can be identified as area V2 and the middle temporal visual area (MT). Three other regions correspond to areas V3, V3A and V4t. Finally, two more regions of labelling have been distinguished that belong to area V4. These results demonstrate that, at least within the central 6 degrees of visual field, all the presently known extrastriate visual cortical areas project to V1. This result is interesting in view of the fact that only a few extrastriate cortical areas are reported to receive afferents from V1. Three groups of cortical areas can be distinguished on the basis of the characteristics of their cortical connections to V1. The first group contains area V2, V3, and the posterior region of V4. These areas project to V1 with infra- as well as supragranular layer neurons and show limited axonal arborization and scatter in the projection. The second group consists of two regions of labelling in the superior temporal sulcus corresponding to V4t and MT and another on the annectant gyrus (V3A). These regions contain almost exclusively infragranular labelling and show wide axonal arborization and scatter in their projections to V1.(ABSTRACT TRUNCATED AT 400 WORDS)     

Organization of galanin-immunoreactive inputs to the paraventricular nucleus with special reference to their relationship to catecholaminergic afferents

Immunohistochemical and axonal transport techniques were used to characterize the origin and distribution of galanin-immunoreactive inputs to the paraventricular (PVH) and supraoptic (SO) nuclei of the hypothalamus in the rat. In the parvicellular division of the PVH, the most prominent inputs were confined to the anterior and periventricular parts of the nucleus rostrally and the dorsal and ventral medial subdivisions caudally; the galaninergic inputs to the magnocellular division of PVH and SO were very sparse and were preferentially distributed to regions containing predominantly oxytocinergic neurons. A combined retrograde transport-immunohistochemical method was employed to identify sources of these projections. Galanin immunoreactivity was found to coexist with dopamine-beta-hydroxylase (DBH) immunoreactivity in subsets of retrogradely labeled neurons of the A1 and A6 (locus coeruleus) catecholamine cell groups; no evidence was adduced for the presence of galanin in adrenergic (i.e., phenylethanolamine-N-methyltransferase-positive) neurons that project to the PVH. Apart from minor contributions from the mesencephalic raphe nuclei, no other brainstem cell groups contributed to the galaninergic innervation of the PVH. In the forebrain, the most prominent grouping of doubly labeled cells was centered in the rostral part of the dorsomedial nucleus of the hypothalamus (DMH), though significant numbers were also found in the lateral hypothalamic area, the arcuate nucleus, and the medial preoptic area. In experiments designed to define the subnuclear specificity of some galanin-containing inputs to the PVH, iontophoretic deposits of the anterogradely transported plant lectin, Phaseolus vulgaris-leucoagglutinin (PHA-L), were placed in the A1 and A6 cell groups and in the DMH. Sections through the PVH were prepared so as to allow colocalization of anterogradely transported PHA-L and galanin immunoreactivity in individual fibers and varicosities. Consistent with the retrograde transport data, the greatest degree of galanin-PHA-L correspondence was seen after lectin deposits in the DMH, and over 80% of the doubly labeled varicosities were confined to the anterior, periventricular, and medial parvicellular subdivisions of the nucleus. The galanin-containing projection from the locus coeruleus was most circumscribed, with the vast majority of doubly labeled varicosities confined to the periventricular and adjoining aspects of the anterior and medial parvicellular subdivisions.(ABSTRACT TRUNCATED AT 400 WORDS)     

Age-related accumulation of Marinesco bodies and lipofuscin in rhesus monkey midbrain dopamine neurons: relevance to selective neuronal vulnerability

Parkinson's disease (PD) is characterized by degeneration of nigrostriatal dopamine (DA) neurons. Although aging is a primary risk factor for PD, its role in DA neuron degeneration remains unknown. Neurodegeneration in PD is not uniform throughout the ventral midbrain: the ventral tier of the substantia nigra (vtSN) is most vulnerable, whereas the dorsal tier (dtSN) and ventral tegmental area (VTA) are relatively resistant. We studied young (9-10 years old), middle-aged (14-17 years old), and old-aged (22-29 years old) rhesus monkeys to identify factors potentially underlying selective vulnerability and their association with aging. We focused on markers relevant to the ubiquitin-proteasome (UPS) and lysosome systems. Unbiased stereological counting was performed on tyrosine hydroxylase-positive (TH+) neurons and TH+ neurons containing Marinesco bodies (TH+MB) or lipofuscin (TH+lipo), markers of UPS or lysosomal activity, respectively. TH+ neuron numbers were inversely correlated with advancing age specifically in the vtSN, not the dtSN or VTA. TH intensity decreased throughout the ventral midbrain with increasing age, an effect exacerbated in the vtSN. TH+MB neurons were localized in the vulnerable vtSN of old monkeys. The number of MBs per cell increased with age, and TH intensity of TH+MB neurons decreased in middle age. Conversely, TH+lipo neurons were primarily found in the resistant dtSN and VTA. These data suggest that particular age-related changes localize to DAergic subregions relevant to degenerative patterns in PD. Furthermore, the results begin to characterize the nature of the link between aging and PD, and they support the concept that aged monkeys represent a valuable model for studying specific events preceding PD.     

银杏内酯B对大鼠下丘脑室旁核神经元自发放电的影响

目的研究银杏内酯B（GinkgolideB，BN52021）对静息状态下的下丘脑脑片室旁核神经元自发放电活动的影响。方法应用细胞外记录单位放电技术。结果（1）在27个下丘脑室旁核神经元放电单位给予银杏内酯B（0．1，1，10μmol／L）2分钟，有26个放电单位（96．30％）放电频率明显降低，且呈剂量依赖性；（2）预先用0．2mmol／L的L—glutamate（L-Glu）灌流下丘脑脑片，8个放电单位放电频率明显增加，表现为癫痫样放电，在此基础上灌流银杏内酯B（1μmol／L）2分钟，其癫痫样放电全部被抑制；（3）预先用L型钙通道开放剂BayK8644灌流8个下丘脑脑片，8个放电单位（100％）全部放电增加，在此基础上灌流银杏内酯B（1μmol／L）2分钟，8个放电单位（100％1放电频率明显减低（4）在8个下丘脑室旁核神经元放电单位上，银杏内酯B（1μmol／L）的抑制效应可被广泛钾通道阻断剂（tetraethylammonium，TEA）1mmol／L完全阻断。结论银杏内酯B（GinkgolideB，BN520211可抑制下丘脑室旁核神经元自发放电，并可抑制由L—glutamate诱发的神经元放电。提示银杏内酯B对心血管中枢神经元通过降低其活动而具有一定程度的保护作用，这种作用可能与银杏内酯B抑制L型钙通道有关，而且可能与延迟整流型钾通道（delayed rectifier potassium channel，KDR）有关。     

Cytochemical study on the effect of aluminum on neuronal Golgi apparatus and lysosomes

Summary Ultracytochemical reactions for enzymatic markers were applied to study the effect of aluminum on some cell organelles of neurons in the Ammon cortex and spinal cord in rabbits. The results showed that aluminum caused an appearance of secondary lysosomes and an increase in the number of lysosomes. The latter finding was endorsed by statistical analysis of Ammon neurons using a two-sidedt-test. Concomitantly, decrease of the intensity of the rection for thiamine pyrophosphatase (TPPase) and nucleoside diphosphatase (NDPase) in the Golgi apparatus was found. The reaction for NDPase in the endoplasmic reticulum remained unchanged. Cytochemical reactions for alkaline phosphatase and Mg²⁺-activated adenosine triphosphatase in the plasmalemma of neurons were negative both in control and in aluminum-treated animals.Our data point to the activation of the system of intracellular digestion and suppression of the enzymatic activities (NDPase, TPPase) of the Golgi apparatus in CNS neurons of rabbits treated with aluminum.Supported in part by a grant from the Aluminum Association