Demonstration of a 2d LH-RH neurosecretory system in the duck hypothalamus]

Using immunocytochemical techniques with an anti-LH-RH immuneserum, evidence of two neuronal systems secreting LH-RH has been shown in the Duck hypothalamus. In addition to the previously described system, located in the preoptic nucleus, a second system could be demonstrated in the infundibular nucleus. The perikarya of the infundibular LH-RH producing neurons were significantly smaller than those of the preoptic neurons. On the other hand, under the experimental conditions used, the infundibular system had approximately five times less LH-RH secreting neurons than the preoptic system, and its perikarya appeared less heavily loaded in IR LH-RH. The LH-RH containing axons from both neuronal populations ran down to the external layer of the median eminence, where they ended in close contact with the capillaries of the hypophysial portal system.     

Inhibition of LH-RH induced release of gonadotropins by substance P in cultured rat anterior pituitary cells]

Using anterior pituitary cells cultured for 7 days and then incubated for 4 hrs, substance P, an undecapeptide, inhibited the stimulatory effect of LH-RH on the release of LH-RH on the release of LH and FSH. This inhibitory effect, which was similar for both gonadotropins was only observed when the adenopituitary cells were put in culture at DI and Proestrus stages of the oestrous cycle. Furthermore substance P partly inhibited the basal release of FSH at DI and DII stages but did never affected that of LH.     

Comparison of the time courses of luteinizing hormone (LH) secretion rates during continuous stimulation by LH-releasing hormone (LH-RH) in vivo and in vitro

Summary The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization.     

Comparison of the time courses of luteinizing hormone (LH) secretion rates during continuous stimulation by LH-releasing hormone (LH-RH) in vivo and in vitro

The patterns of LH secretion during constant stimulation of the pituitary glands of estradiol-treated ovariectomized rats with a maximally stimulating amount of LH-RH in vivo and in vitro correspond with each other qualitatively and quantitatively. In vitro the changes with time of the LH secretion rate are somewhat retarded, especially the occurrence of desensitization.     

Immunohistochemical detection of a substance resembling growth hormone-releasing factor in the brain of the rainbow trout (Salmo gairdneri)

We studied the distribution of an immunoreactive substance resembling growth hormone-releasing factor (GRF) in the hypothalamus and pituitary gland of the rainbow trout by immunofluorescence methods. The GRF-like immunoreactive perikaryon was observed in colchicine-treated fish. The majority of GRF-containing neurons were located in the nucleus lateral tuberis; others were located in the caudal part of the preoptic nucleus of the hypothalamus. The GRF-like immunoreactive neuronal processes projected into the pars distalis via the pars nervosa of the pituitary gland. The distribution of the GRF-like immunoreactive substance in the hypothalamus and pituitary gland suggests that GRF plays a physiological role in the regulation of growth hormone release from the pituitary gland of rainbow trout, as it does in mammals.     

The hypothalamus and the neurobiology of drug seeking

The hypothalamus is a neural structure critical for expression of motivated behaviours that ensure survival of the individual and the species. It is a heterogeneous structure, generally recognised to have four distinct regions in the rostrocaudal axis (preoptic, supraoptic, tuberal and mammillary). The tuberal hypothalamus in particular has been implicated in the neural control of appetitive motivation, including feeding and drug seeking. Here we review the role of the tuberal hypothalamus in appetitive motivation. First, we review evidence that different regions of the hypothalamus exert opposing control over feeding. We then review evidence that a similar bi-directional regulation characterises hypothalamic contributions to drug seeking and reward seeking. Lateral regions of the dorsal tuberal hypothalamus are important for promoting reinstatement of drug seeking, whereas medial regions of the dorsal tuberal hypothalamus are important for inhibiting this drug seeking after extinction training. Finally, we review evidence that these different roles for medial versus lateral dorsal tuberal hypothalamus in promoting or preventing reinstatement of drug seeking are mediated, at least in part, by different populations of hypothalamic neurons as well as the neural circuits in which they are located.     

Immunohistochemical detection of a substance resembling growth hormone-releasing factor in the brain of the rainbow trout (Salmo gairdneri)

Summary We studied the distribution of an immunoreactive substance resembling growth hormone-releasing factor (GRF) in the hypothalamus and pituitary gland of the rainbow trout by immunofluorescence methods. The GRF-like immunoreactive perikaryon was observed in colchicine-treated fish. The majority of GRF-containing neurons were located in the nucleus lateral tuberis; others were located in the caudal part of the preoptic nucleus of the hypothalamus. The GRF-like immunoreactive neuronal processes projected into the pars distalis via the pars nervosa of the pituitary gland. The distribution of the GRF-like immunoreactive substance in the hypothalamus and pituitary gland suggests that GRF plays a physiological role in the regulation of growth hormone release from the pituitary gland of rainbow trout, as it does in mammals.     

Insulin acts on the hypothalamic glucose-facilitated neurons to induce hyperglycemia and hyperinsulinemia in the rat

Microinjection of insulin (0.04-0.12 IU/microliter) into the anterior hypothalamus or the lateral hypothalamus, but not the ventromedial hypothalamus of the rat brain, caused a dose-dependent rise in blood glucose and in serum insulin. The majority (71.5%) of the glucose-facilitated neurons recorded in the lateral hypothalamic area were excited by intracerebral injection of insulin. The data indicate that insulin acts on the hypothalamic glucose-facilitated neurons to induce hyperglycemia and hyperinsulinemia. It is unknown whether insulin normally reaches the hypothalamic area, or how it might do so.     

Effects of gonadotropin-releasing hormone (LH-RH) on the pars distalis and testis of the Skipper frog,rana cyanophlyctis (Schn.)

Summary Administration of LH-RH to adult male Skipper frogs resulted in marked hypertrophy and degranulation of basophils-2 (B2) in the pars distalis of the pituitary and a significant increase in their nuclear and cellular area. Concomitantly, there is a significant increase in the relative weight of the testes, in the number of cell nests containing secondary spermatogonia and primary spermatocytes, and in the nuclear diameter of the Leydig cells. There is also an increase in the ⁵-3-hydroxysteroid dehydrogenase and glucose-6-phosphate dehydrogenase activities in the Leydig cells. The results indicate that the B2 cells are gonadotrops and the hormone(s) secreted by B2 cells regulate the spermatogenetic and steroidogenic activity of the testis inR. cyanophlyctis.The free gift of LH-RH from NIH is gratefully acknowledged. Authors are grateful to CSIR, New Delhi, for the award of a SRF to the first author and to Karnatak University, Dharwad for providing laboratory facilities.     

Topographic localisation of insulinogenic and insulinoprival areas in the hypothalamus

Summary Electrical stimulation of hypothalamic areas through stereotaxically implanted electrodes were carried out in conscious male rhesus monkeys. There was a significant increase in immunoreactive insulin (IRI) following lateral hypothalamus (LHA) stimulation. An opposite response was obtained from ventromedial hypothalamus (VMH). Thus, insulinogenic and insulinoprival responses were obtained from feeding and satiety, suggesting a significant role of insulin in the regulation of food intake.     

Topographic localisation of insulinogenic and insulinoprival areas in the hypothalamus.

Electrical stimulation of hypothalamic areas through stereotaxically implanted electrodes were carried out in conscious male rhesus monkeys. There was a significant increase in immunoreactive insulin (IRI) following laterla hypothalamus (LHA) stimulation. An opposite response was obtained from ventromedial hypothalamus (VMH). Thus, insulinogenic and insulinoprival responses were obtained from feeding and satiety, suggesting a significant role of insulin in the regulation of food intake.     

Insulin acts on the hypothalamic glucose-facilitated neurons to induce hyperglycemia and hyperinsulinemia in the rat

Microinjection of insulin (0.04–0.12 IU/l) into the anterior hypothalamus or the lateral hypothalamus, but not the vertromedial hypothalamus of the rat brain, caused a dose-dependent rise in blood glucose and in serum insulin. The majority (71.5%) of the glucose-facilitated neurons recorded in the lateral hypothalamic area were excited by intracerebral injection of insulin. The data indicate that insulni acts on the hypothalamic glucose-facilitated neurons to induce hyperglycemia and hyperinsulinemia. It is unknown whether insulin normally reaches the hypothalamic area, or how it might do so.This work was supported by grants from the National Science Council (Taipei, Taiwan, Republic of China).     

Age variation in the increase of hypothalamic and brain stem contents of phenylethanolamine m-octopamine and p-octopamine in spontaneously hypertensive rats (SH Kyoto).

Phenylethanolamine, m-octopamine and p-octopamine contents were determined as a function of age in the hypothalamus and brain stem of spontaneously hypertensive rats and controls Wistar Kyoto. In hypothalamus, the content of the 3 amines was 2--4-fold greater for the SH rats. In the brain stem, the phenylethanolamine and p-octopamine contents were 2--3-fold greater in SH rats but 5--6-fold higher in the case of m-octopamine. The difference appears at 3 weeks and correlates the blood pressure with the increase of age. The significance of these findings is discussed.     

The effects of lesions in several zones of the brain on cell multiplication in the glandular epithelium of the rat small intestine]

Radio-frequency lesions of tubero-infundibular region of the hypothalamus are followed by a significant increase of the mitotic rate in the small intestine glandular epithelium in rats. This increase does not occur when radio-frequency lesions are located in the anterior and posterior hypothalamus, in the dorsomedial thalamus and in the cerebral hemispheres.     

Effect of an LH-RH antagonist on reproductive status of immature female rats.

Administration of the LH-RH antagonist, D-Phe2-D-Ala6-LH-RH (Wy-18, 185) to immature female rats from days 25--35 of age was without significant effect on day of vaginal opening (puberal onset), weights of the ovaries, uteri and anterior pituitary, and on ovarian histology on autopsy day 39.     

Altered brain cholinergic enzymes activity in the genetically obese rat

Genetically obese male Zucker rats (fa/fa) and their lean littermates (Fa/-) were used in this experiment. Fourteen-week-old obese and lean littermates were sacrificed and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) enzymes were assayed in specific brain regions. The assays of these enzymes indicate that obese animals had a significantly lower ChAT activity in the cerebellum, pons, and cerebral cortex and a significant increase in ChAT activity in the thalamus and hypothalamus. Meanwhile, the cerebral cortex, cerebellum, midbrain, thalamus and hypothalamus of the obese animals showed significantly higher AChE activity than their lean littermates. It was concluded from this study that obesity may be associated with changes in the enzymes of the brain cholinergic system.     

Effects of castration, estradiol and testosterone on tubulin levels of the medial basal hypothalamus and the adenohypophysis of the rat.

Tubulin levels of the medial basal hypothalamus (MBH) were greater in male than in female rats. Orchidectomy brought about a decrease of MBH tubulin concentration, whereas testosterone injection augmented it in the MBH and adenohypophysis. Estradiol administration augmented MBH tubulin and protein concentration.     

The hypothalamic somatostatinergic pathways mediate feeding behavior in the rat

The level of somatostatin in the hypothalamus was higher in satiated rats than in hungry rats. Elevating hypothalamic somatostatin levels by administering somatostatin into the hypothalamus produced a decrease in food intake, whereas lowering hypothalamic somatostatin levels by administering cysteamine into the peritoneal cavity produced an increase in food intake in rats.     

Effects of ovariectomy on the oxidative metabolism of the central nervous system and adrenal glands in female hamster (Mesocricetus auratus)

We have studied the influence of ovariectomy on the oxidative activity of hypophysis, hypothalamus, posterior cortex, septal area, amygdala and adrenal glands, in female hamsters, because their neuroendocrine behavior seems to differ from that of rats. Our results show a decreasing the O2 uptake in the hypothalamus and adrenal glands and an increase in the rest of the structures.     

Effects of ovariectomy on the oxidative metabolism of the central nervous system and adrenal glands in female hamster (Mesocricetus auratus)

Summary We have studied the influence of ovariectomy on the oxidative activity of hypophysis, hypothalamus, posterior cortex, septal area, amygdala and adrenal glands, in female hamsters, because their neuroendocrine behavior seems to differ from that of rats. Our results show a decreasing the O₂ uptake in the hypothalamus and adrenal glands and an increase in the rest of the structures.