Female sexual behaviour: roles of gonadal hormones in the Syrian hamster

The sexual behaviour of ovariectomized female hamsters was examined after treatment with oestrogen alone and after the addition of progesterone. Both the proceptive and receptive components of behaviour were recorded at four oestrogen dose levels; progesterone dose was kept constant. Oestrogen alone caused dose-dependent increases in proceptive behaviour and, at the higher dose levels, a small increase in receptivity. The addition of progesterone increased proceptive behaviour in females primed with the lower dose of oestrogen but not the higher. Receptivity was markedly increased in all animals but the intensity of lordosis was oestrogen-dose dependent.     

A Golgi analysis of neuronal organization in the medial cerebellar nucleus of the rat.

The neurons of the medial cerebellar nucleus of the rat were studied with several variants of the Golgi technique. Using the criteria of somatic size, dendritic pattern and location, seven cell types were designated within the nucleus. Large multipolar neurons were most prominent in dorsal portions of the nucleus while small multipolar and fan-shaped neurons predominate ventrally. The rostral and caudal halves of the medial nucleus differ in their neuronal orientation. There is a caudolateral to rostromedial cellular orientation in the caudal portion of the nucleus, and a caudomedial to rostrolateral orientation in the rostro-ventral part of the medial nucleus. The large multipolar neurons of the rostro-dorsal region display no special orientation. In addition to these rostral and caudal architectural differences, there are several longitudinal zones within the medial nucleus previously reported in Nissl preparations (Beitz &; Chan-Palay, 1978). The medial and lateral elliptical zones are comprised predominantly of neurons of the nuclear boundary, fan-shaped neurons and small bipolar neurons. The round cell central zone, by contrast, is comprised primarily of small and large multipolar neurons and bouquet neurons.We conclude that the medial cerebellar nucleus consists of several distinct regions each with a characteristic arrangement of its constituent cells and that these regions correspond to those previously reported as having different physiological functions.     

The cytoarchitecture of the adult human parabrachial nucleus: a Nissl and Golgi study

The parabrachial nucleus (PBN) plays important roles in numerous autonomic functions and in pain modulation. In different animal species, three main regions of the PBN have been identified: the m-PB, the l-PB, and the Kolliker-Fuse nucleus (KF). The KF has not been identified in humans. The present study used Nissl and Golgi-Cox material and morphoquantitative methods to investigate the cytoarchitectural organization of the adult human PBN, paying particular attention to neuronal features endowed with functional significance, i. e. the arborization of the neurons. The PBN neuron population is made up of elements which are heterogeneous in size, shape and dendritic arborization, and grouped into two regions, the lateral and medial PBN (l- and m-PB). It has been suggested that some large sized neurons located in the ventral region of the m-PB might be the counterpart of the KF. In the m-PB the fusiform neurons are the most numerous cells; in the l-PB the multipolar neurons prevail, and are particularly numerous in the dorsal l-PB. Since the dendritic arborization is generally the main target of afferent projections to a neuron, it is possible that the l-PB, and in particular its dorsal region, might be the main site for the endings of afferences to the human PBN.     

Taste responses of neurons in the hamster solitary nucleus are modulated by the central nucleus of the amygdala

Previous studies have shown a modulatory influence of forebrain gustatory areas, such as the gustatory cortex and lateral hypothalamus, on the activity of taste-responsive cells in the nucleus of the solitary tract (NST). The central nucleus of the amygdala (CeA), which receives gustatory afferent information, also exerts descending control over taste neurons in the parabrachial nuclei (PbN) of the pons. The present studies were designed to investigate the role of descending amgydaloid projections to the NST in the modulation of gustatory activity. Extracellular action potentials were recorded from 109 taste-responsive cells in the NST of urethan-anesthetized hamsters and analyzed for a change in excitability following electrical and chemical stimulation of the CeA. Electrical stimulation of the CeA orthodromically modulated 36 of 109 (33.0%) taste-responsive NST cells. An excitatory response was observed in 33 (30.28%) cells. An initial decrease in excitability to electrical stimulation of the CeA, suggestive of postsynaptic inhibition, was observed in three (2.75%) NST taste cells. NST cells modulated by the CeA were significantly less responsive to taste stimuli than cells that were not. Many of these cells were under the modulatory influence of the contralateral CeA (28/36 = 77.8%) as well as the ipsilateral (22/36 = 61.1%); 14 (38.9%) were excited bilaterally. Latencies for excitation were longer after ipsilateral than after contralateral CeA stimulation. Microinjection of DL-homocysteic acid (DLH) into the CeA mimicked the effect of electrical stimulation on each of the nine cells tested: DLH excited eight and inhibited one of these electrically activated NST cells. Application of subthreshold electrical stimulation to the CeA during taste trials increased the taste responses of every CeA-responsive NST cell (n = 7) tested with this protocol. These effects would enhance taste discriminability by increasing the signal-to-noise ratio of taste-evoked activity.     

Aberrant neuronal physiology in the basal nucleus of the amygdala in a model of chronic limbic epilepsy

Limbic epilepsy is a chronic condition associated with a broad zone of seizure onset and pathology. Studies have focused mainly on the hippocampus, but there are indications that changes occur in other regions of the limbic system. This study used in vitro intracellular recording and histology to examine alterations to the physiology and anatomy of the basal nucleus of the amygdala in a rat model of chronic limbic epilepsy characterized by spontaneously recurring seizures. Epileptic pyramidal neuron responses evoked by stria terminalis stimulation revealed hyperexcitability characterized by multiple action potential bursts and no evident inhibitory potentials. In contrast, no hyperexcitability was observed in amygdalar neurons from kindled (included as a control for seizure activity) or control rats. Blockade of ionotropic glutamate receptors unmasked inhibitory postsynaptic potentials in epileptic pyramidal neurons. Control, kindled and epileptic inhibitory potentials were predominantly biphasic, with fast and slow components, but a few cells exhibited only the fast component (2/12 in controls, 0/3 in kindled, 3/10 in epileptic). Epileptic fast inhibitory potentials had a more rapid onset and shorter duration than control and kindled. Approximately 40% of control neurons exhibited spontaneous inhibitory potentials; no spontaneous inhibitory potentials were observed in neurons from kindled or epileptic rats. A preliminary histological examination revealed no gross alterations in the basal amygdala from epileptic animals.These results extend previous findings from this laboratory that hyperexcitability is found in multiple epileptic limbic regions and may be secondary to multiple alterations in excitatory and inhibitory efficacy. Because there were no differences between control and kindled animals, the changes observed in the epileptic animals are unlikely to be secondary to recurrent seizures.     

Development and hormonal regulation of mast cells in the Harderian gland of Syrian hamsters

Summary The morphological features and relative number of mast cells per mm² were studied in the Harderian glands of male and female Syrian hamsters (Mesocricetus auratus) under different experimental conditions. The structural and ultrastructural characteristics of Harderian mast cells corresponded to those of connective tissue mast cells. The Harderian glands from female hamsters contained more mast cells than those of male hamsters. A subcutaneous implant of testosterone (2 mg/24 mg beeswax) resulted in a rapid decrease in the number of recognizable mast cells 6 h after the implantation. Neither orchidectomy nor ovariectomy significantly altered the relative number of mast cells. However, the daily subcutaneous injection of 20 IU of human chorionic gonadotropin during 20 days resulted in a significant decrease of identifiable mast cells. The administration of another steroid such as progesterone or the induction of states of hypo- and hyperthyroidism did not alter the distribution of mast cells in the Harderian glands of female Syrian hamsters.     

Golgi type II interneurons in the neuronal circuit of the monkey lateral geniculate nucleus

Summary Total excision of areas 17-18-19 in the monkey leads to disappearance of relay cells and corticogeniculate axon terminals in the LGN (lateral geniculate nucleus). The few remaining neurons can be safely considered as Golgi type II cells. Electron microscopic examination of such material revealed small ovoid neurons and synaptic clusters encapsulated by glia. Within the cluster there were the characteristic axon terminal of retinal origin, and a peculiar light and large profile with features of both axons (small, flattened synaptic vesicles) and dendrites (many microtubules, endoplasmic cisterns and free ribosomes) in varying proportions. These elements were also present within the heavily gliotic general neuropil and, in longitudinal section, showed segments with strongly dendritic features, and others with vesicles either scattered or grouped near synaptic specializations. Similar profiles were also seen in normal LGN. Light microscopic examination of Golgi series from adult normal monkeys revealed two types of interneurons in the LGN, both having extremely thin axons which could not correspond in size to the ambiguous profiles described above. The latter could well match the appendages so frequently shown by the dendrites of one of the interneuron types. These findings suggest that the synapses in the glomeruli of LGN previously defined as axo-axonic may in fact be between optic axon terminals and the dendritic profiles with synaptic vesicles delineated in this study. Thence, the role of the Golgi type II interneuron could be interpreted at least in part as lateral inhibition.This research was supported in part by U.S.P.H.S. Grants MH-02261 and K3-EY-16, 865. The technical assistance of Mr. David Kahn and Miss Rosemary Lang is gratefully acknowledged.     

Immunohistochemical localization of antioxidant enzymes in adult Syrian hamster tissues and during kidney development.

Tissues from adult Syrian hamsters were studied with immunoperoxidase techniques using polyclonal antibodies to three antioxidant enzymes (copper, zinc and manganese forms of superoxide dismutase, and catalase). Tissues from labile organs, in which cell renewal is prominent (uterus, intestine, and transitional epithelium of the urinary tract), showed strong antioxidant enzyme immunostaining in differentiated cells but not in stem cells. In stable organs, in which cell renewal occurs at a high rate only in response to injury (kidney and adrenal), each cell type showed a specific pattern of antioxidant enzyme immunostaining. In permanent organs (brain and heart), antioxidant enzymes were regionally specific markers. Axons of the cerebellum showed more intense antioxidant enzyme staining than those of the cerebral cortex; in the heart, atria stained more intensely than ventricles. Germ cells of the testis resembled cell renewal systems in their antioxidant enzyme-immunostaining pattern: spermatogonia were negative, whereas spermatozoa were strongly positive. The tubules of the kidney showed no antioxidant enzyme immunostaining until after birth. Our results suggest that there is a prominent role for antioxidant enzymes in cell differentiation during development and cell renewal.     

The perineuronal net in the fastigial nucleus of the rat cerebellum. A Golgi and quantitative study

Summary The morphological study of the rat fastigial nucleus with the Golgi-Rio Hortega method showed the presence of glial perineuronal nets surrounding the large neurons, but not the small ones. This perineuronal net appeared as a mesh of tenuous glial processes which covers the neuronal perikarya and proximal dendrites. The small alveolate compartments in this mesh seem to correspond to the holes for the synaptic boutons. Our results also indicate that the perineuronal net is derived from interneuronal protoplasmic and velate astrocytes.Using camera lucida drawings of this perineuronal net we have made a quantitative estimation of the size and density of synaptic boutons on these large neurons. The average numerical density of synaptic boutons was about 19 per 100 m² of the neuronal surface, the mean area of the synaptic holes being 2.5 m². Furthermore, the quantitative data evidence that about 52.5% of the neuronal surface is presumably occupied by synaptic boutons whereas the remaining 47.5% is covered by the glial processes of the perineuronal net.Semithin sections prepared from thick Golgi sections were used for the cytological study of the neurons surrounded by this glial pericellular network. The possible functional significance of the perineuronal net in the regulation of synaptic transmission in the fastigial cerebellar nucleus is briefly discussed.     

The bed nucleus of the stria terminalis in the Syrian hamster: subnuclei and connections of the posterior division

The bed nucleus of the stria terminalis is a key part of a ring of cells extending between the centromedial amygdala and bed nucleus of the stria terminalis referred to as the extended amygdala. The present study describes the architecture of the bed nucleus of the stria terminalis and the connections of subnuclei in posterior bed nucleus of the stria terminalis. The hamster bed nucleus of the stria terminalis is readily allotted to anterior and posterior divisions separated by the fibers of the body of the anterior commissure. The anterior division has four subnuclei: anteromedial, anterointermediate, anterolateral, and anteroventral. Within the posterior division, there are three distinct regions: posteromedial, posterointermediate, and posterolateral. In hamsters, the posterior bed nucleus of the stria terminalis contributes to male sexual behavior, particularly chemoinvestigation. Moreover, the posterior bed nucleus of the stria terminalis is part of a neural circuit essential for mating, including the medial amygdaloid nucleus and medial preoptic area. The connections of bed nucleus of the stria terminalis, posteromedial part, bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posterolateral part were visualized by co-injection of anterograde (Phaseolus vulgaris leucoagglutinin) and retrograde (cholera toxin B) tract tracers. The bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posteromedial part have dense bidirectional connections with medial amygdaloid nucleus and cortical amygdala via the stria terminalis and ventral amygdalofugal pathway. These subnuclei also maintain bidirectional connections with steroid-concentrating areas including lateral septum, medial preoptic area, hypothalamus, and periaqueductal gray. The bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posteromedial part receive projections from the subiculum and send projections to deep mesencephalic nuclei. By contrast, the bed nucleus of the stria terminalis, posterolateral part is connected with the central amygdala, lateral hypothalamus, subthalamic nucleus, nucleus accumbens, substantia innominata, substantia nigra and thalamus. Thus, the bed nucleus of the stria terminalis, posterointermediate part and bed nucleus of the stria terminalis, posteromedial part have similar connections with areas involved in social behaviors. The bed nucleus of the stria terminalis, posterolateral part maintains connections with areas involved in motivational circuits. This supports the concept of distinct circuits within the extended amygdala which differentially link the centromedial amygdala and bed nucleus of the stria terminalis.     

Synaptic organization of the dorsal lateral geniculate nucleus in the adult hamster

Summary The synaptic organization of the sector of the dorsal lateral geniculate nucleus has been examined by electron microscopy in normal adult hamsters and in adult hamsters subjected to unilateral eye enucleation or intravitreal injection of horseradish peroxidase.Two types of neuropil are apparent. Islands of complex neuropil partially enclosed by astrocyte processes (synaptic glomeruli) are surrounded by a sea of simpler non-glomerular neuropil. The latter is dominated by small axon terminals with spherical synaptic vesicles and Gray type 1 axodendritic contacts (SR-boutons) and also contains axon terminals with flattened synaptic vesicles (F-boutons). The glomerular neuropil contains (i) exclusively postsynaptic dendrites and dendritic protrusions of presumptive projection cells; (ii) pre- and postsynaptic pleomorphic-vesiclecontaining P-boutons (interpreted as appendages of the dendrites of interneurons); (iii) large axon terminals containing spherical synaptic vesicles and large pale mitochondria (R-boutons) which were experimentally identified as retinal terminals and which are presynaptic to both projection cell dendrites and P-boutons at Gray type 1 contacts; (iv) F-boutons (minority component). F-boutons and P-boutons are presynaptic to both projection cell dendrites and P-boutons and P-boutons are the intermediate elements of various serial synapses including triplet (triadic) synapses. Medium-large terminals with spherical synatpic vesicles and dark mitochondria (RLD-boutons) which were commonly invaginated by dendritic spines of projection cells in small glomerulus-like formations were also identified. The origin of RLD-boutons is unknown but SR-boutons probably derive chiefly from ipsilateral visual cortex and possibly also from superior colliculus, and non-glomerular F-boutons probably originate in the ipsilateral thalamic reticular nucleus.No differences in synaptic organization were found between the part of the nucleus which receives uncrossed retinal input and the part which receives crossed input, nor were differences seen in the size, fine structure or relationships between the terminals of identified crossed and uncrossed retinal axons.     

Development of the rabbit visual cortex: A quantitative Golgi analysis

Summary The horizontal and vertical components of the positions of both eyes of rhesus monkeys were measured during periods of binocularly stable eye positions (eye pauses) while the animals fixated a small target. Differences between monocular and binocular viewing, as well as effects of target size and background illumination, were assessed and found to be comparable to similar measures for humans. The scatter of eye position for either eye during binocular viewing had a standard deviation of 6–8 min arc in the horizontal and 7–13 min arc in the vertical meridia. Measurements of vergence and vertical misalignment, taken from binocular positional disparity, showed that for nearly 60% of eye pause time the eyes were misaligned on the fixation target by more than 7 min arc along both horizontal and vertical axes. In addition, the line of gaze during the trial was found to follow certain idiosyncratic tendencies for each monkey, although the positional variability remained relatively constant throughout the fixation trial. These observations suggest that during binocular fusion and stereopsis a mechanism exists that dynamically compensates for the relatively large shifts in retinal image position during fixation.Supported by NIH Grant EY02966     

A Golgi Type II neuron in trigeminal nucleus oralis: a Golgi study in the rat

This Golgi study identifies a class of small neurons in trigeminal nucleus oralis (Vo) that satisfies all the morphological criteria for a Golgi Type II neuron. The cylindrical-shaped dendritic arbor extends up to 500 micron in the rostrocaudal axis and is confined to Vo. The unmyelinated axon generates a highly branched collateral axonal plexus within or near the dendritic tree and it does not project out of Vo. This Golgi Type II neuron is considered to be an inhibitory interneuron and probably participates in a variety of inhibitory phenomena known to occur in Vo.     

The hypoglossal nucleus of the primate: a Golgi study

The neurons of the hypoglossal nucleus were examined in Golgi preparations of adult macaque and squirrel monkeys. Two distinct types of neurons were found. The first type was a large multipolar cell which was typical of the majority of the neurons of the nucleus. Its soma ranged in size from 18 to 50 micrometers and numerous dendrites emerged from it. The dendritic spread of these neurons was within the ipsilateral nucleus, across the midline into the contralateral hypoglossal nucleus, or out into the adjacent reticular formation. The second type of neuron was a small cell. The soma of this neuron was oval in shape, measured less than 20 micrometers in its largest diameter, and gave off only two or three dendrites which remained within the nucleus.     

Dendritic changes in the basal nucleus of Meynert and in the diagonal band nucleus in Alzheimer's disease--a quantitative Golgi investigation

Golgi-impregnated reticular neurons and multipolar giant neurons, the two main classes of neurons in the basal nucleus of Meynert and in the diagonal band nucleus, were investigated morphometrically in five cases of Alzheimer's disease, and compared to controls. Both degenerative as well as regenerative neuronal changes were observed in cases of Alzheimer's disease. Degenerative changes such as irregular swellings and the fragmentation of dendrites are most pronounced on reticular neurons but can also be detected to a lesser extent on multipolar giant neurons. Regenerative changes are restricted to reticular neurons. They are characterized by the appearance of perisomatic filopodia, by an increase in the size of cell soma, by an increase in the degree of dendritic arborization and spatial extension of the dendritic tree. These regenerative changes are probably signs of a compensatory mechanism which might be induced by degeneration in this area.     

Immunohistochemical localization of glutathione-S-transferase and glutathione peroxidase in adult Syrian hamster tissues and during kidney development.

Tissues from adult Syrian hamsters were studied with immunoperoxidase techniques using polyclonal antibodies to glutathione-S-transferase (rat liver and human placental enzymes) and human erythrocyte glutathione peroxidase. Most tissues immunostained similarly with these antibodies. Most notable was the cytoplasmic staining of mesenchyme tissues, especially smooth muscle, by all three antibodies. Epithelial cells stained distinctively, but usually less intensely than mesenchyme. Epithelial cells from all levels of the gastrointestinal tract, respiratory epithelium, transitional epithelium, and epidermis all showed strong staining with these antibodies. Other epithelial cell types were usually positive but showed less dramatic staining. Most epithelial tissues showed both nuclear and cytoplasmic staining; some also showed cell-surface (eg, cilia) staining. The role of these enzymes in cell differentiation of a stable organ was studied by immunostaining the kidney during its development. Early stroma (13- and 15-day fetuses) of the kidney (metanephric mesenchyme) showed strong cell-surface staining for glutathione transferases and moderate staining for glutathione peroxidase; renal tubules (which are epithelial cells) at this stage were negative for these markers. As renal tubules differentiated, first cytoplasm and then nuclei stained moderately, suggesting that glutathione-S-transferases and glutathione peroxidase are markers of both mesenchymal cells, including embryonic mesenchyme, and terminal differentiation of at least some epithelial cells.     

The main olfactory system mediates pheromone-induced fos expression in the extended amygdala and preoptic area of the male Syrian hamster

Copulation in male hamsters is stimulated by exposure to vaginal secretions of conspecifics. These pheromones also stimulate fos expression in neural areas that regulate copulation including: the medial nucleus of the amygdala, the bed nucleus of the stria terminalis, and the preoptic area. The pheromones in vaginal secretions are detected by both the main and accessory olfactory systems. However, the accessory system plays the greater role in the regulation of mating behavior and has direct connections with the medial nucleus of the amygdala and bed nucleus of the stria terminalis. The goal of the present study was to determine which system mediates the effect of pheromones on the stimulation of more central areas by deafferenting these systems in experienced male hamsters before exposure to vaginal secretions. Destruction of the receptors in the main olfactory system with zinc sulfate eliminated the increase in fos immunoreactivity in the amygdala, bed nucleus of the stria terminalis and preoptic area following exposure to sexually stimulating pheromones. Deafferentation of the accessory olfactory system by removing the vomeronasal organ had no effect on pheromone-induced fos expression in these areas.We conclude that neurons expressing fos following exposure to vaginal secretions are stimulated via the main olfactory system and are not associated with the expression of copulatory behavior.