摘要:

The hypogonadal mouse, which lacks gonadotropin-releasing hormone, has been suggested as an animal model of Kallmann’s syndrome, one symptom of which is hyposmia. We have determined the metabolic activity of the olfactory system, in normal and hypogonadal mice, using [14C]-2-deoxyglucose quantitative autoradiography. In the olfactory lobes, deoxyglucose uptake was greatest in the glomerular and granule cell layers and low in the olfactory nerve layer and bulb core. The pattern of uptake was similar in both hypogonadal and normal mice breathing filtered air. Exposure of normal mice to ethyl acetoacetate significantly increased deoxyglucose uptake in the olfactory nerve layer and glomerular layer, but not in the granule cell layer. Several foci of intense metabolic activity were produced, apparently corresponding to small groups of activated glomeruli. There were no changes in the secondary or tertiary projections of the olfactory system. In hypogonadal mice, ethyl acetoacetate failed to increase the number of foci and the density of labelling in the olfactory nerve layer and glomerular layer. These data show that the functional activity of the olfactory system in hypogonadal mice breathing air is apparently normal. However, the olfactory response to ethyl acetoacetate is significantly less in hypogonadal mice. Whether this is due to their lack of gonadotropin-releasing hormone requires further experimentatio

ISSN:0028-3835    

DOI:10.1159/000124947

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

The aim of the present study was to determine which of the anterior or posterior efferents of the suprachiasmatic nucleus (SCN) predominantly act for the maintenance of estrous cycle in female rats. A small knife (0.8 mm in radius) was used for anterior (ASD), posterior (PSD) and complete suprachiasmatic deafferentations (CSD). The rats subjected to CSD were divided into two groups, the first group bearing lesions on the medial preoptic nucleus (MPN; group CSD-MPN-L) and the other group bearing no lesions on the MPN (group CSD). For reference, anterior hypothalamic deafferentation (AHD) was carried out using a large knife (2.0 mm in radius). All rats with AHD or CSD-MPN-L and some of CSD rats showed persistent estrus, but all animals with ASD or PSD resumed regular estrous cycles after transient irregular periods. Ovaries of AHD, CSD and CSD-MPN-L rats contained very few, if any, corpora lutea, while the number of corpora lutea in ASD or PSD rats was not significantly different from that of sham-operated controls. Immunohistochemical examination revealed that in AHD rats LHRH immunoreactivity in the median eminence was markedly reduced as compared with that of sham-operated controls. In contrast, in ASD, PSD, CSD and CSD-MPN-L rats, the LHRH immunoreactivity in the median eminence was similar to that of sham-operated controls. These results indicate that estrous cycle and spontaneous ovulation can be maintained if about half of the SCN projections, either from the anterior or posterior routes, are left intact and that persistent anovulatory estrus induced by CSD is not due to the interruption of LHRH fibers, but is simply due to the complete isolation of the SCN from other parts of the brain. Additional observations on wheel-running activity showed that the behavioral circadian rhythm was abolished in CSD and CSD-MPN-L rats. Estrogen-induced daily LH surges were not observed in CSD and CSD-MPN-L rats. Progesterone-induced LH surge was not prevented, but was significantly reduced in CSD animals. However, in CSD-MPN-L rats the rise in LH level after progesterone treatment failed to occur. These results suggest that the SCN exerts its influence, through its anterior and/or posterior routes, on the neural mechanism participating in the positive feedback effect of estrogen.

ISSN:0028-3835    

DOI:10.1159/000124948

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

Hypothalamic lesions of serotoninergic afferents following bilateral stereotoxic injections of the neurotoxin 5,7-dihydroxytryptamine (5,7-DHT) into the region of the ventromedial hypothalamus enhanced the effects of hormonally induced lordosis responding in both male and female rats. However, similarities and differences in the enhanced responsiveness to ovarian hormones were observed between the sexes. Compared with sham-lesioned controls, lesioned males displayed elevated lordosis responding to estradiol (E) priming alone, as well as to priming with E followed by progesterone (P). On the other hand, lesioned females displayed elevated lordosis in response to E priming alone, but were not different from controls in a synergistic facilitation of lordosis by P after E priming. With respect to receptivity, neither lesioned nor control males displayed ear-wiggling and hop-darting in response to E + P, whereas both lesioned and control females were proceptive following this treatment. Therefore, hypothalamic lesions following 5,7-DHT increase lordosis, but fail to unmask in males the responsiveness to E + P priming mediating proceptive behaviours by females. Further, the levels of lordosis responding displayed by lesioned males are lower than those of either lesioned or control females after E + P priming, as well as those of lesioned females after E priming alone, thus indicating that other inhibitory mechanisms continue to operate in the lesioned males.

ISSN:0028-3835    

DOI:10.1159/000124949

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

Distribution and staining intensities of growth hormone releasing factor (GRF) and somatostatin (SRIF) were examined in young (3 months of age) and old (24 months of age) male rats of Sprague-Dawley strain, using the PAP immunocytochemical procedure. Some animals of each age group were intraventricularly injected with colchicine to demonstrate immunoreactive neuronal perikarya. GRF-immunoreactive intensities of old rats were markedly reduced in the median eminence as compared with those of young rats. No remarkable difference could be detected between SRIF immunoreactivities in the young and old animals, since intensive SRIF immunoreactivities were found in the external layer of the median eminence of both groups of animals. Between two age groups injected with colchicine, we also found no difference in the distribution and staining intensities of immunoreactive perikarya of GRF and SRIF in the hypothalamus and also detected no significant difference in total neuron numbers of each peptide. These findings suggest that the synthesis and/or release of GRF in GRF-containing neurons are decreased, though GRF-containing neurons themselves remain alive and have the capacity to synthesize GRF.

ISSN:0028-3835    

DOI:10.1159/000124950

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

To determine whether neuroexcitatory amino acids may play a role in generating intermittent hypothalamic GnRH release, the effect of N-methyl-D-aspartate (NMDA) receptor blockade on pulsatile LH secretion was examined in male rats. The ability of the NMDA receptor antagonist, DL-2-amino-5-phosphonopentanoic acid (AP5), to inhibit activation of the hypothalamic-pituitary gonadotroph axis that follows peripheral administration of NMDA, was first established in intact rats. Subsequently, acutely castrated rats (n = 12) bearing venous catheters received four consecutive intravenous injections of AP5 (3.75 mg/injection/rat; approx. 13.6 mg/kg BW/injection) at 15-min intervals. Blood samples were collected at 10-min intervals for 1 h before and 2 h after initiation of AP5 treatment, and plasma LH concentrations were determined by RI A. For control purposes, norvaline, an amino acid structurally related to AP5, was administered to a second group of animals (n = 7) in a quantity (2.25 mg/injection/rat; approx. 8.2 mg/kg BW/injection) equimolar to that of the NMDA receptor antagonist. A third group of animals (n = 8) received only saline, the vehicle employed to inject AP5 and norvaline. AP5, but not norvaline, resulted in a marked suppression of pulsatile LH secretion. These findings suggest that neuroexcitatory amino acids acting at the NMDA receptor may play a physiological role in generating the intermittent mode of hypothalamic GnRH release.

ISSN:0028-3835    

DOI:10.1159/000124951

出版商:S. Karger AG    

年代:1988

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000124952

出版商:S. Karger AG    

年代:1988

数据来源: Karger

摘要:

The distributions of somatocrinin (GHRF) and neuropeptide Y (NPY) immunoreactivities were compared in the infundibular area of the human hypothalamus. About 40% of the arcuate GHRF-stained perikarya were found to costain for NPY, while in the peripheral neurovascular zone of the median eminence the two stainings appeared dissociated. Therefore, it is concluded that a wide population of hypothalamic neurons producing a GHRF-related peptide does not project to the pituitary portal plexus and is thus not involved in the direct neurohemal control of the pituitary somatotropic secretion.

ISSN:0028-3835    

DOI:10.1159/000124953

出版商:S. Karger AG    

年代:1988

数据来源: Karger