摘要:

Lesions were made in various hypothalamic and preoptic regions in sexually mature female and male goldfish. Destruction of the pituitary stalk, and lateral anterior hypothalamic tract areas caused ovulation and increased serum gonadotropin levels. Destruction of the entire preoptic region or a major part of the anterior nucleus preopticus periventricularis also caused ovulation and increased serum GtH levels. Lesions in other locations were ineffective. The results indicate that a gonadotropin release-inhibitory factor (GRIF) probably originates in the anterior preoptic region, and reaches the pituitary via pathways in the lateral preoptic and lateral anterior hypothalamic regions, and the pituitary stalk. The preovulatory surge of gonadotropin secretion may be regulated by release from inhibition exerted by GRIF in goldfish.

ISSN:0028-3835    

DOI:10.1159/000123064

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effects of immobilization stress on the activity of the adrenaline-forming enzyme, phenylethanolamine N-methyltransferase (PNMT), have been studied in discrete areas of the rat brain stem and hypothalamus. The changes in brain PNMT activity varied with the duration of the stress, were localized to a few brain areas, and the direction of the change varied with the area considered. PNMT was increased after acute immobilization in several areas of the brain stem: A2 area, the anterior part of the nucleus tractus solitarius, and the locus coeruleus. After 7 days of stress, significantly increased PNMT activity was found only in the A2 area and in the cerebellum. In the anterior hypothalamic nucleus, immobilization stress repeated for seven days resulted in a significant decrease in methyltransferase activity. These results implicate discrete, localized adrenaline-forming neurons in the central regulation of the stress response.

ISSN:0028-3835    

DOI:10.1159/000123065

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The purpose of this study was to determine which specific structures within the medial preoptic-anterior hypothalamic area are necessary to maintain cyclic ovulation in the rat, and to define the deficit(s) in the feedback regulation of gonadotropin secretion associated with lesions that result in anovulation. Large (∼1.1 mm dia.) or small (∼0.7 mm dia.) electrolytic lesions were placed in several loci within preoptic, anterior hypothalamic and suprachiasmatic areas in regularly cycling adult female rats. Large lesions which included the suprachiasmatic nuclei (SCN) induced an anovulatory condition characterized by persistent vaginal cornification and polyfollicular ovaries (persistent estrus). Large or small lesions which included the medial preoptic nucleus (MPN), a small periventricular column of cells located immediately caudal to the organum vasculosum of the lamina terminalis (OVLT), also induced persistent estrus. Lesions placed elsewhere within the medial preoptic-anterior hypothalamic area never induced persistent estrus but were frequently associated with repeated periods of prolonged diestrus separated by brief periods of vaginal cornification. These prolonged diestrous intervals appeared to be related to spontaneous luteal activation following ovulation rather than impaired folliculogenesis. LH and FSH surges induced by sequential administration of estradiol benzoate and progesterone (P) were completely abolished only by lesions which included the MPN. Small lesions involving only the MPN and OVLT or the MPN and caudally adjacent loci in the suprachiasmatic region were as effective in this respect as larger lesions encompassing most of the preoptic-suprachiasmatic region from the diagonal band of Broca to the rostral pole of the SCN. On the other hand, P-induced gonadotropin surges were never completely blocked by SCN lesions, although the magnitude of the surge was highly variable and frequently attenuated compared to controls. It is concluded that both the MPN and SCN are required for the long-term maintenance of spontaneous cyclic ovulation in the rat. However, the characteristically dissimilar deficits in P-induced gonadotropin release associated with lesions of one or the other of these structures indicate that these nuclei may play different roles in the regulation of gonadotropin surges. It is suggested that neural elements indispensable for phasic gonadotropin release are located within and/or immediately adjacent to the MPN. The SCN may influence phasic gonadotropin release indirectly, by regulating circadian rhythms which govern the responsiveness of other neural elements to hormonal stim

ISSN:0028-3835    

DOI:10.1159/000123066

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

We measured the concentration of oxytocin and vasopressin in microdissected areas of the hypothalamus and posterior pituitary in weanling and adult female rats. Oxytocin concentration was significantly less in adult rats as compared to weanling rats in the supraoptic nucleus, median eminence, and retrochiasmatic area with no significant differences in vasopressin content. This may indicate differences in hypothalamic-neurohypophyseal pathways in adult and weanling rats. There was a significantly greater concentration of oxytocin in the adult rat in the paraventricular nucleus, suprachiasmatic nucleus, anterior hypothalamic nucleus, and posterior pituitary, again with no significant difference in vasopressin concentration. Our results are consistent with a role for sexual maturation in increasing synthesis of oxytocin in specific hypothalamic nuclei resulting in increased storage of oxytocin in the posterior pituitary.

ISSN:0028-3835    

DOI:10.1159/000123067

出版商:S. Karger AG    

年代:1980

数据来源: Karger