摘要:

The effect of pinealectomy (PX) and sham-pinealectomy (SPX) on the calculated concentration of NaCl in the total volume of fluid drunk per day ([NaCl]i) in female rats offered a free choice between water and 3% NaCl solution was measured. In normal rats the [NaCl]i increases after attainment of sexual maturity. The increase can be accelerated by neonatal PX. Neonatal ‘masculinization’ of female rats by testosterone propionate (TP2) removes the increase of [NaCl]i in adult females and suppresses the acceleration due to PX. Neonatal SPX interferes with this decreasing effect of TP2 in adult female rats. The role of the pineal gland in the regulation of water and salt intake is discussed in relation to sex differences, sexual maturation and neonatal str

ISSN:0028-3835    

DOI:10.1159/000122393

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The effects of acute stress on norepinephrine (NE) and dopamine (DA) concentrations and of repeated stress on tyrosine hydroxylase (TH) activity were measured in individual hypothalamic nuclei and other rat brain regions. A microdissection technique and radioisotopic enzymatic assays enabled these studies to be performed. NE and DA concentrations were reduced and TH activity increased selectively in the arcuate nucleus. These results suggest that the arcuate nucleus may be selectively involved in the stress response and support the hypothesis that catecholamìnes in the medial basal hypothalamus mediate certain of the neuroendocrine changes observed in stress

ISSN:0028-3835    

DOI:10.1159/000122394

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The effects of dorsal, ventral, and near-total hippocampal lesions upon both rhythmic and stress-induced corticosterone secretion in adult male rats were examined. All hippocampally-damaged, cortically-damaged, and intact rats showed rhythmic corticosterone secretion as measured in 4 blood samples for each animal taken at 6-h intervals at least 1 week apart. There were no significant differences among the groups. In addition, there were no significant differences in the amount of stress-induced corticosterone across experimental groups.

ISSN:0028-3835    

DOI:10.1159/000122395

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Intravenous injection of the synthetic tripeptide (PyroGlu-His-Pro-NH2: TRH) effected the prompt release of TSH and prolactin (PRL) from the pituitary of the goitrous rat. Plasma TSH and PRL levels increased 2-3-fold within 1 min after the injection of 0.4 and 2 µg TRH. Intravenous injection of 20 µg of L-thyroxine (T4) induced repletion of TSH to supranormal levels in the adenohypophysis of goitrous rats without a significant change in PRL stores. The acute administration of TRH (2 and 50 µg) to rats after pituitary TSH rebound resulted in a simultaneous increase in circulating levels of the pituitary hormones; this was correlated with the prompt and vigorous extrusion of secretory granules from the pituitary cells. PRL content of the pituitary increased. A relationship was found in rats between the amount of TRH ingested in drinking water and plasma levels of PRL and TSH; hormonal stores in the adenohypophysis usually declined. Ingestion of large amounts of TRH (1,700 µg daily for 8 and 14 days) by the euthyroid rat resulted in a 2–3-fold elevation of the plasma TSH level. In PTU(propylthiouracil)-treated rats ingesting approximately the same amount of TRH, a plasma TSH increase failed to occur. The oral ingestion of TRH for 22–27 days by goitrous, TSH-rebounded rats resulted in a significant diminution in the circulating levels of TSH and PRL, and in ultrastructural manifestations suggestive of impaired release by the adenohypophysis. It is concluded that the acute administration of TRH causes the rapid release of TSH and PRL from the pituitary of the chronically hypothyroid rat. The intensity of the response to TRH is enhanced after pituitary TSH rebound, and synthesis of PRL appears to be augmented. Chronic oral administration of TRH to the goitrous rat results in a diminished release of the pituitary hormones, despite ample stores in th

ISSN:0028-3835    

DOI:10.1159/000122396

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The effects of electrical stimulation of the medial preoptic area (MPO) upon unit firing in the periventricular arcuate nucleus, and that of the dorsal hippocampus (DHPC) on medial septo-preoptic and arcuate (ARC) neurons, were investigated in Wistar and Sprague-Dawley female rats throughout the 4-day estrous cycle. Unit activity was recorded using stereotaxically-oriented tungsten microelectrodes under light urethane anesthesia. Repetitive stimulation of monophasic square waves varying only in current intensity was used. The following results were obtained: (a) An increase in activity of all ARC neurons recorded was induced by MPO stimulation on each day of the estrous cycle, (b) The minimum current (threshold) effective in increasing activity in the ARC neurons varied throughout the estrous cycle; the lowest threshold was observed in proestrus and the highest on the first day of diestrus. Also, the threshold current of MPO stimulation required to increase ARC activity was found to be elevated after ovariectomy and markedly reduced to the levels of the prcestrous animal by estrogen treatment, (c) Stimulation of the DHPC (field CA3) increased activity in the medial septum but decreased activity in the MPO. Two pools of neurons, one increased and one decreased by DHPC stimulation, were observed in the ARC. (d) Variation in the threshold hippocampal stimulation during the estrous cycle was observed in the response of MPO and ARC neurons (the stimulation was effective only in proestrus and estrus), but not in that of medial septal neurons, (e) In addition, the spontaneous activity of septal, MPO, and ARC neurons was increased at proestrus or after estrogen injection. The present results suggest that plasma levels of estrogen play an essential role in the cyclic process of the regulation of ovulation by way of the selective facilitation of neuronal excitability in specific functional neural pathways.

ISSN:0028-3835    

DOI:10.1159/000122397

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The effect of pretreatment with α-methyl-p-tyrosine (α-MT) on the basal levels of plasma growth hormone (GH) and the responses to chlorpromazine (CPZ) were investigated in urethane-anesthetized rats with either complete hypothalamic deafferentation (CD.), hypothalamic ablation (H.A.) or sham operation (Sham). Basal GH levels were high in C.D. rats, intermediate in H.A. rats, and low in Sham rats without any pretreatment. Pretreatment with α-MT caused a significant increase in basal GH levels in both C.D. and Sham rats, but not in H.A. rats. GH release following the intravenous injection of CPZ, which was observed in C.D. and Sham rats without α-MT pretreatment, was blunted by treatment with α-MT. In H.A. rats CPZ failed to stimulate the secretion of GH regardless of α-MT pretreatment. Neither the injection of L-DOPA nor L-DOPA affected basal GH levels in non-α-MT pretreated C.D. rats. However, plasma GH levels significantly decreased following the injection of L-DOPA but not L-DOPA in C.D. rats pretreated with α-MT. These findings suggest that the injection of CPZ causes an enhancement of GH release by inhibiting the catecholaminergic (dopaminergic) mechanism, which is active within the basal medial hypothalamus (BMH) and plays an inhibitory role in GH secretion. They also suggest that the extrahypothalamic inhibitory neural pathway, which is connected to the BMH and is interrupted by hypothalamic deafferentation, is not catecholam

ISSN:0028-3835    

DOI:10.1159/000122398

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

No significant change in hypothalamic TRH content was found in rats during acute (5–240 min) exposure to cold (5 °C), in spite of rapid and sustained elevations in plasma TSH and thyroxine. Plasma PRL rose markedly in the first 15 min, but returned to normal thereafter. Chronic exposure to cold (32 days) was characterized by elevated plasma and pituitary levels of both TSH and PRL in the presence of an unaltered hypothalamic TRH content. If increased TRH release from the hypothalamus occurs during exposure to cold, as suggested by the pituitary-thyroid stimulation, either it is compensated for by an equal rise in synthesis, or the extra amount released is negligible in comparison with the hypothalamic content of TRH. The acute PRL response to exposure to cold may be related to an acute TRH release but could also result from the accompanying stress response acting by a mechanism independent of T

ISSN:0028-3835    

DOI:10.1159/000122399

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Sodium glutamate infused into the 3rd ventricle is a potent stimulus of ACTH release, as shown by the rise in plasma corticosterone levels. Glutamate failed to consistently increase the plasma corticosterone level in rats with deafferentation of the medial basal hypothalamus (MBH). We suggest that intraventricular glutamate interferes with central nervous function outside the MBH and stimulates ACTH release via afferent neural pathways.

ISSN:0028-3835    

DOI:10.1159/000122400

出版商:S. Karger AG    

年代:1975

数据来源: Karger