Effects of dehydroepiandrosterone on ovarian cystogenesis and immune function.

The purpose of the present report was to study the possible relationship between ovarian functionality and the immune response during cystogenesis induced by androgenization with dehydroepiandrosterone (DHEA). Daily injection of DHEA (6 mg/kg body weight) for 20 consecutive days induced ovarian cysts in BALB/c mice. As markers of ovarian function, serum estradiol (E) and progesterone (P) and the ovarian inmunomodulator prostaglandin E (PGE) were analyzed.

Changes of melanin-concentrating hormone related to LHRH release in the median eminence of rats.

The present research was carried out to study the distribution of melanin-concentrating hormone (MCH) fibers in the median eminence of rats and to evaluate if changes in the MCH content of the median eminence could be related to the release of LHRH. Immunocytochemical studies in the median eminence of males and estrous females showed the presence of MCH fibers, mainly in its internal layer. Diestrous and proestrous animals displayed MCH immunoreactivity in both the internal and external layers of the median eminence.

Neural control of the compensatory increase of testosterone in hemicastrated adult male rats.

It is unclear why the concentration of testosterone increases in the testicular vein after hemicastration without corresponding alteration in gonadotropins. The present work was undertaken to examine whether the testosterone levels could be modified by denervation of the testis in adult rats. Both systemic and testicular blood samples were collected either immediately before or 6 and 24 hours after hemicastration from the rats two weeks after denervation of either inferior spermatic nerves (ISN) or ISN plus superior spermatic nerves (ISN-SSN).

Peptidergic innervation of blood vessels and interstitial cells in the testis of the cat.

We studied the innervation of the cat testis using a panel of antisera against the following neuronal markers: protein gene product 9.5 (PGP), neuropeptide Y, C-terminal peptide of neuropeptide Y, galanin, vasoactive intestinal peptide (VIP), calcitonin gene-related peptide, and substance P. Immunoreactivity against PGP, a general neuronal label, demonstrated the arrangement of fibers from the superior spermatic nerve (SSN) in the testicular pedicle and the cephalic testicular pole, and those of the inferior spermatic nerve (ISN) along the vas deferens and the inferior testicular ligament.

[Vasoactive intestinal polypeptide induced prolactin release is model dependent in free-moving rats].

Our previous experiments in vitro showed that the stimulating effects of vasoactive intestinal polypeptide (VIP) on pituitary (PRL) depended on the endocrinal status of the animals. The present investigation was to determine whether the effect of VIP varied in vivo with changes of different physiological conditions. For infusion of VIP (5 micrograms/100 g body weight) and collection of blood sample, all the animals were cannulated with silicon tube into jugular vein 2-3 d before the experiments.

Melanin-concentrating hormone stimulates the release of luteinizing hormone-releasing hormone and gonadotropins in the female rat acting at both median eminence and pituitary levels.

The purpose of this study was to investigate whether melanin-concentrating hormone (MCH) acts directly on the median eminence and on the anterior pituitary of female rats regulating LHRH and gonadotropin release. In addition, immunohistochemistry was used to examine the density and distribution of MCH-immunoreactive fibers in the median eminence of proestrous rats. MCH-immunoreactive fibers were found in both the internal and external layers of the median eminence and in close association with hypophysial portal vessels.

Growth Hormone (GH) but not IGF-I-Secretion is Stimulated in Aged Rats by Chronic Hexarelin and GHRP-6 administration.

The present studies were designed to investigate in aged rats (22-24 months old) the effectiveness and specificity of acute hexarelin (HEXA) administration on the release of growth hormone (GH), the minimal dose of the peptide that produces the maximal GH secretion and the effects of long term treatment with HEXA or growth hormone releasing peptide (GHRP-6) on plasma levels of GH and IGF-1. To select the appropriate anesthetic to obtain serial blood samples, the GH releasing activity of HEXA (30 µg/kg i.v.

Differential effects of superior and inferior spermatic nerves on testosterone secretion and spermatic blood flow in cats.

It has been postulated that testosterone secretion is partially regulated by signals from the spermatic nerves. To further examine this hypothesis in vivo, the superior (SSN) or the inferior (ISN) spermatic nerves were stimulated electrically (varying intensity, 25 Hz, 0.2 msec, 10 min) in anesthetized cats, determining the testosterone concentration and the blood flow in the spermatic vein.

Testicular denervation-induced nuclear changes in Leydig cell of hemicastrated adult rats.

In the adult male rat, hemicastration (HC) induces a remarkable enhancement of testosterone secretion from the Leydig cells of the remaining testis. We have observed previously that the denervation of inferior spermatic nerves inhibits this enhancement. The present experiments were designed to assess morphometrically whether or not this change had a cytological correlate in Leydig cells.

Involvement of Catecholestrogens in the release of pituitary hormones.

Catecholestrogens (CE), natural metabolic products of 17ß-estradiol and estrone, were assayed in anterior and posterior pituitary lobes and in the median eminence of the rat. The highest CE values were found in the median eminence and the lowest in the anterior pituitary. The CE concentrations in pars nervosa and pars intermedia of the posterior pituitary were quite similar.

Monoaminergic and peptidergic contributions of the superior and the inferior spermatic nerves to the innervation of the testis in the rat.

Sections of the rat testis and whole-mounts of the testicular capsule were studied microscopically using the glyoxylic acid-induced fluorescence method, to detect monoamines, and immunohistochemical procedures for the detection of immunoreactivities to protein gene-product 9.5 (PGP 9.5), the C-terminal accompanying peptide of neuropeptide Y (CPON), and vasoactive intestinal polypeptide (VIP).

Serotonin, a neurotransmitter involved in the regulation of luteinizing hormone release.

The involvement of serotonin (5-HT) in the regulation of LH secretion is discussed on the basis of experimental and physiological models. The role of 5-HT on low amplitude pulsatile LH release in male rats is not yet clear, in spite of the fact that recent results suggest a weak permissive role. In ovariectomized rats, 5-HT expresses a negative influence on the increased rate of LH release, which is converted into a stimulatory effect by pretreatment of the animals with E2.

Effect of bilateral denervation of the immature rat testis on testicular gonadotropin receptors and in vitro androgen production.

We have studied the effect of superior spermatic nerve (SSN) section on testicular gonadotropin receptors and in vitro androgen production by immature rat testis. Bilateral testicular denervation had no effect on testicular weight, serum androgens, LH, FSH and PRL levels. Denervation resulted in a significant inhibition of hCG stimulated in vitro androgen production.

Epidermal growth factor stimulates thyrotropin secretion in the rat.

The present work studied the effects of epidermal growth factor (EGF) on the release of thyrotropin (TSH) and prolactin (PRL) from perifused pituitary glands of 200-gram male Wistar rats. Each pituitary gland, cut into halves, was placed in a chamber of a perifusion system connected to a peristaltic pump which conveyed the perifusion medium (Medium 199, pH 7.3, Gibco, USA) from a reservoir to a chamber at a flow rate of 100 microliters/min.

Suckling-induced changes of vasoactive intestinal peptide concentrations in hypothalamic areas implicated in the control of prolactin release.

The present study was designed to investigate whether the vasoactive intestinal peptide (VIP) concentration in hypothalamic nuclei, dorsal raphe nucleus (DR) and pituitary lobes of lactating rats changes in physiological situations when prolactin (PRL) secretion is stimulated (suckling) or inhibited (pup separation). In addition VIP levels in blood plasma were determined in both situations. Acute suckling induced changes in VIP concentration only in the rostral part of the anterior hypothalamic (rAHN) and the paraventricular (PVN) nuclei of all the brain areas examined.

[The effect of epidermal growth factor on thyrotropin secretion in rats].

The present work studied the effects of epidermal growth factor (EGF) on the secretion of thyrotropin (TSH) from perifused pituitaries of 200 g body weight male Wistar rats. After decapitation the neural lobe was discarded and the anterior pituitary was transferred to a chamber of a perifusion system connected to a peristaltic pump which conveyed the perifusion medium (Medium 199) through a reservoir to a chamber at a flow rate of 100 microliters/min. Individual chambers were filled with 600 microliters of medium and placed in a water bath at 37 degrees C.

Catecholamine distribution in adult rat testis.

Catecholamine distribution in the adult rat testis was examined using a sensitive radioenzymatic method. Norepinephrine was present in the capsule and the interstitial fluid, in higher concentrations than dopamine, while in the interstitial cell preparations only norepinephrine was found. Epinephrine was undetectable in all testicular compartments investigated.

Serotonergic innervation of the rat testis.

The presence of 5-hydroxytryptamine (5-HT) was determined by h.p.l.

Dorsal raphe lesion alters the estrous cycle and the preovulatory gonadotropin release.

The purpose of this study was to examine the role that the dorsal raphe (DR)-median eminence (ME) serotonergic projection may have in the proestrous gonadotropin and prolactin (PRL) release. DR electrolytic lesions were performed in cycling rats during the first day of diestrus. The effect of DR lesions after 48-72 h of survival (short-term lesioned animals) or after 35-40 days of survival (long-term lesioned animals) on estrous cyclicity, preovulatory gonadotropin and PRL releasing pattern, ovulation and serotonin (5-HT) content of the ME were studied.

Serotonergic terminals in the anterior hypothalamic nucleus involved in the prolactin release during suckling.

The present studies were designed to localize within the hypothalamus and neighboring areas the serotonergic terminals which are implicated in suckling-induced PRL release. The initial experiments were performed to characterize the circulating hormone profile induced by suckling in lactating rats, previously separated from their pups. Five minutes of suckling induced an increase in serum PRL only.

Serotonin induces gonadotrophin release through stimulation of LH-releasing hormone release from the median eminence.

The effects of serotonin (5-HT) on the release of gonadotrophins and LH-releasing hormone (LHRH) were examined in an in-vitro perifusion system using median eminences and/or anterior pituitaries obtained from male or pro-oestrous female rats. Animals were killed by decapitation between 12.00 and 13.

Dopamine enters lactotrophs and reaches their secretory granules.

The presence of dopamine in the lactotroph cell, as well as in isolated prolactin secretory granules, was demonstrated by means of an histochemical reaction for electron microscopy. Biochemical assays further confirmed the presence of dopamine in the secretory granules. Autoradiographic preparations examined by light microscopy showed dopamine internalization in dispersed anterior pituitary cells.

Serotonin stimulates gonadotrophin release by acting directly on the median eminence.

The study examined the effect of serotonin (5-HT) on gonadotrophin release and its tissue site of action using a sequential double chamber perifusion system. Cycling female rats were killed between 12.00 and 13.

Origin and termination of dorsal raphe-median eminence projection.

The origin and termination of the dorsal raphe (DR)-median eminence (ME) projection were studied by combining well-limited small electrolytic lesions of different parts of the DR, the axonal degeneration and the serotonin content in the median eminence. Our results show that the rostral third of the DR is a source of serotonergic innervation to the ME and that the rest of the nucleus does not contribute to this projection. The light microscopy study revealed that degenerating fibers occupy the internal layer of the ME.