Ida Gerendai

Neuronal Labeling in the Rat Brain and Spinal Cord from the Ovary Using Viral Transneuronal Tracing Technique

In the present investigations the viral transneuronal labeling method, which is able to reveal hierarchial chains of central nervous system (CNS) neurons, was applied to identify sites in the CNS connected with the ovary and presumably involved in the control of ovarian functions. Pseudorabies virus was injected into the ovaries of rats and a few days later (at various times after the injection) the spinal cord and brain were examined for virus-infected neurons from the ovary. The virus-labeled nerve cells were identified by immunocytochemistry using polyclonal antiviral antibody. Virus-labeled neurons were detected both in the spinal cord and the brain. In the spinal cord such elements were observed in the intermediolateral cell column, in the dorsal horn close to the marginal zone and in the central autonomic nucleus. In the medulla oblongata and pons, neurons of several nuclei and cell groups (area postrema, nucleus of the solitary tract, dorsal vagal complex, nucleus ambiguus, paragigantocellular nucleus, parapyramidal nucleus, A1, A5 and A7 cell groups, caudal raphe nuclei, locus ceruleus, subceruleus nucleus, Barrington’s nucleus, Kölliker-Fuse nucleus) were found to be transneuronally labeled. In the mesencephalon, the ventrolateral part of the periaqueductal gray matter contained virus-labeled neurons. In the diencephalon, a very intensive cell body labeling was observed in the hypothalamic paraventricular nucleus and a few virus-infected neurons could be detected in the lateral and dorsal hypothalamus, in the arcuate nucleus, zona incerta, perifornical area and in the anterior hypothalamus. Concerning the telencephalic structures, virus-labeled cells were found in the bed nucleus of the stria terminalis and in the central amygdala nucleus. These findings provide the first neuromorphological evidence for the existence of a multisynaptic neuronal pathway between the ovary and the CNS, and give a detailed account of the structures involved in this pathway.

Unilateral ovariectomy-induced luteinizing hormone-releasing hormone content changes in the two halves of the mediobasal hypothalamus

The luteinizing hormone-releasing hormone (LHRH) content of the two halves of the mediobasal hypothalamus (MBH) has been studied two weeks after unilateral or bilateral ovariectomy (OVX) in the rat. In control animals, the LHRH content of the right-side MBH was higher than that of the left side. Right-side OVX induced a significant increase in LHRH content on the right-side MBH while left-side OVX was followed by elevated LHRH content on the left-side MBH. In contrast, bilateral OVX induced a significant decrease on the right-side MBH. The observation that unilateral OVX induced increased LHRH content in the ipsilateral half of the MBH to OVX, supports the view that a neural pathway might connect the ovary and the MBH.

The hypothalamic levels of the endocannabinoid, anandamide, peak immediately before the onset of puberty in female rats

Several data suggest that the endogenous cannabinoid system plays a role in neuroendocrine regulation in adult individuals, although the information on its involvement in peri-pubertal processes is scarce. In the present study, we have examined the ontogeny (from postnatal day [PND] 5 up to adulthood) of hypothalamic and anterior pituitary contents of anandamide (arachidonyl-ethanolamide, AEA). We observed that the content of AEA in the hypothalamus was low at PND5, PND15 and PND25, but it markedly increased (approximately 3-fold) immediately before the puberty (on the day of 1st proestrus), to return to intermediate values immediately after the vaginal opening (day of 2nd proestrus) and, eventually, adulthood. By contrast, no consistent differences were observed in AEA levels in the anterior pituitary. These results demonstrate the occurrence of a parallelism between the peri-pubertal events and a rise in the hypothalamic content of AEA immediately before the puberty, which might indicate that this endocannabinoid may be involved in the onset of puberty in rats.

Participation of a Pure Neuronal Mechanism in the Control of Gonadal Functions

The present review summarizes the data on the existence of a neural connection between the gonads and the central nervous system. As an experimental model the development of compensatory ovarian hypertrophy following unilateral ovariectomy was studied. Unilateral ovariectomy or orchidectomy resulted in a higher cellular activity in the hypothalamic arcuate neurons contralateral to hemigonadectomy and an increased luteinizing hormone‐releasing hormone content in the medio‐basal hypothalamus ipsilateral to the removed gonad. Local treatment of the remaining ovary with 6‐hydroxy‐dopamine prevented the development of compensatory ovarian hypertrophy after unilateral ovariectomy. Hemitransection of the spinal cord contralateral to hemigonadectomy, different unilateral hypothalamic deafferentations of the medio‐basal hypothalamus as well as unilateral lesion of the medial preoptic area or of the arcuate nucleus blocked the compensatory ovarian growth when the brain surgery was on the same side as ovariectomy. Furthermore, in hypophysectomized + unilaterally ovariectomized rats a less severe ovarian atrophy occurred than in animals solely with hypophysectomy. All these data favour the view that – besides the hormonal control – a pure neuronal mechanism is also involved in the regulation of gonadal functions.

Hemigonadectomy-Induced Unilateral Changes in the Protein-Synthesizing Activity of the Rat Hypothalamic Arcuate Nucleus

The effect of unilateral ovariectomy on the protein-synthesizing activity of the hypothalamic arcuate and dorsomedial nucleus on both sides was studied in vivo as well as in vitro. Four weeks after the removal of 1 ovary, there was a significant increase in labelled amino acid incorporated into the arcuate neurons contralateral to the removed ovary as compared to those incorporated into the nerve cells of the nucleus on the ipsilateral side. In the dorsomedial nucleus, there was no difference between the 2 sides. On the basis of the present findings, the existence of a neural pathway between the ovary and the hypothalamic arcuate nucleus is assumed.

Identification of CNS neurons involved in the innervation of the epididymis: A viral transneuronal tracing study

Cell groups of the spinal cord and the brain transsynaptically connected with the epididymis (caput, cauda) were identified by means of the viral transneuronal tracing technique. Pseudorabies virus was injected into the caput or the cauda epididymidis, and after survival times 4 and 5 days, the spinal cord and brain were processed immunocytochemically. Virus-labeled neurons could be detected in the preganglionic sympathetic neurons (lower thoracic and upper lumbar segments) and following virus injection into the cauda epididymidis, also in the sacral parasympathetic nucleus (L6-S1). Virus-infected perikarya were present in several brain stem nuclei (lateral reticular nucleus, gigantocellular and paragigantocellular nucleus, A5 noradrenergic cell group, caudal raphe nuclei, locus coeruleus, Barringtons nucleus, nucleus of the solitary tract, periaqueductal gray) and in the diencephalon (hypothalamic paraventricular nucleus, lateral hypothalamus). At the longer survival time, some telencephalic structures also exhibited virus-labeled neurons. The distribution of infected neurons in the brain was similar after virus injection into the caput or cauda epididymidis; however, earlier onset of infection was observed after inoculation into the cauda. The present findings provide the first morphological data on a multisynaptic circuit of neurons innervating the epididymis and presumably involved in the control of epididymal functions. reserved.

Recent findings on the organization of central nervous system structures involved in the innervation of endocrine glands and other organs; observations obtained by the transneuronal viral double-labeling technique.

This review summarizes the data obtained with the aid of the recently introduced dual viral tracing technique, which uses isogenic recombinants of pseudorabies virus that express unique reporter gene. This approach made possible to explore simultaneously neural circuits of two organs. The results of these studies indicate: (1) there are neurons innervating exclusively a given organ; (2) left-sided predominance in the supraspinal innervation of the endocrine glands (adrenal, ovary) studied, so far; (3) viral co-infection of neurons, i.e., special neuronal populations coexist in different brain areas that are transsynaptically connected with both paired endocrine and non-endocrine organs, endocrine glands and non-endocrine organs, and organs of bodily systems other than the endocrine one. The number of common neurons seems to be related to the need of coordinating action of different systems. The data on co-infection of neurons suggest that the central nervous system has the capacity to coordinate different organ functions via common brain neurons providing supraspinal innervation of the organs.

Transneuronal labelling of nerve cells in the CNS of female rat from the mammary gland by viral tracing technique

Using the viral transneuronal tracing technique, the cell groups in the CNS transneuronally connected with the female mammary gland were detected. Lactating and non-lactating female rats were infected with pseudorabies virus injected into the mammary gland. The other group of animals was subjected to virus injection into the skin of the back. Four days after virus injection, infected neurons detected by immunocytochemistry, were present in the dorsal root ganglia ipsilateral to inoculation and in the intermediolateral cell column of the spinal cord. In addition, a few labelled cells could be detected in the dorsal horn and in the central autonomic nucleus (lamina X) of the spinal cord. At this survival time several brain stem nuclei including the A5 noradrenergic cell group, the caudal raphe nuclei (raphe obscurus, raphe pallidus, raphe magnus), the A1/C1 noradrenergic and adrenergic cell group, the nucleus of the solitary tract, the area postrema, the gigantocellular reticular nucleus, and the locus coeruleus contained virus-infected neurons. In some animals, additional cell groups, among others the periaqueductal gray and the red nucleus displayed labelling. In the diencephalon, a significant number of virus-infected neurons could be detected in the hypothalamic paraventricular nucleus. In most cases, virus-labelled neurons were present also in the lateral hypothalamus, in the retrochiasmatic area, and in the anterior hypothalamus. In the telencephalon, in some animals a few virus-infected neurons could be found in the preoptic area, in the bed nucleus of the stria terminalis, in the central amygdala, and in the somatosensory cortex. At the longer (5 days) survival time each cell group mentioned displayed immunopositive neurons, and the number of infected cells increased. The pattern of labelling was similar in animals subjected to virus inoculation into the mammary gland and into the skin. The distribution and density of labelling was similar in lactating and non-lactating rats. The present findings provide the first morphological data on the localization of CNS structures connected with the preganglionic neurons of the sympathetic motor system innervating the mammary gland. It may be assumed that the structures found virus-infected belong to the neuronal circuitry involved in the control of the sympathetic motor innervation of the mammary gland.

Cerebral neurons involved in the innervation of both the adrenal gland and the ovary: A double viral tracing study

Previous studies using the viral transneuronal tracing technique demonstrated central autonomic circuits involved in the innervation of the adrenal gland and the ovary. Since the pattern of infection of central nervous system structures is similar after virus inoculation of the adrenal gland and the ovary, and, on the other hand, it is well documented that the activity of the hypothalamo-pituitary-adrenal axis exerts an inhibitory effect on the reproductive system, we investigated whether there are neurons that are transneuronally connected both with the adrenal gland and the ovary. The central circuitry involved in the innervation of the left adrenal and the left ovary was studied in individual rats by dual transneuronal tracing using isogenic recombinant strains (BDG and DS-RED) of Bartha strain of pseudorabies virus. Dual-infected neurons were detected in the ventrolateral medulla, nucleus of the solitary tract, caudal raphe nuclei, A5 cell group, and hypothalamic paraventricular nucleus. The results indicate that there are neurons in the central nervous system that contribute to the transneuronal innervation of both the adrenal gland and the ovary. The data suggest a new type of interaction, i.e. interaction at cellular level that might be involved in regulatory processes integrating the functional activity of the two organs.

Further data on the existence of a neural pathway from the adrenal gland to the hypothalamus

SummaryThe effect of unilateral adrenalectomy on the incorporation of tritiated leucine into the ventromedial nucleus of both sides of the rat hypothalamus was studied by light- and electron-microscopical autoradiography. The left adrenal had been removed and 14 days later labeled amino acid was given intravenously. Rats were killed 5, 30, 60 and 120 min after isotope administration. Following unilateral adrenalectomy there is a marked difference in the autoradiographic reaction of both sides of the hypothalamic ventromedial nucleus. On the right side the number of autoradiographic silver grains is much higher than on the left side, the difference being statistically significant for each animal and for each time interval. In accordance with previous findings the data suggest the existence of a neural pathway from the adrenal gland to the hypothalamus.