摘要:

A brain site of melatonin action has been determined for the white-footed mouse (Peromyscus leucopus). Melatonin-beeswax implants releasing small quantities of melatonin (<100 ng/day) caused a 50% reduction in reproductive tract weight relative to controls (p < 0.025) with 83% of these animals having an imperforate vagina, when implanted in the anterior hypothalamic nuclei (AH) and suprachiasmatic nuclei (SCN). Subcutaneous implants had little effect. Implants in the AH and SCN also had a pronounced effect on both lipid-free interscapular brown fat and nesting behavior. Mice implanted in these regions exhibited a 59% increase in interscapular brown fat and 65% more nesting than controls (both p < 0.01). These results suggest that melatonin acts at a region in the anterior hypothalamus which controls photoperiodic adjustments.

ISSN:0028-3835    

DOI:10.1159/000123269

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Plasma corticosterone levels were determined by protein-binding assay at 2- and 5-min intervals after systemic or neurogenic stress. The same corticosterone (B) profile was observed after hemispherectomy as in intact pigeons, exhibiting episodic increase including several successive peaks after stress application. Hypothalamic stimulation of ACTH injection resulted in a simpler adrenocortical response, analogous to the first peak of the response to stress. Posterolateral deafferentation of the hypothalamus unabled neurogenic stress to promote any plasma B increase and significantly altered the response to systemic stress since only the first peak of B occurred. Such a single peak response to both systemic and neurogenic stresses was observed after surgical interruption of neural connections between hypothalamic and thalamic structures without interferring with posterior afferents to the basal hypothalamus. The role of thalamic-hypothalamic interrelationships in modulating the stress-induced adrenocorticotropic activity is discussed.

ISSN:0028-3835    

DOI:10.1159/000123270

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Hypothalamic dopamine-β-hydroxylase (DBH) activity and plasma luteinizing hormone (LH) concentrations were analyzed in female C57BL/6 mice aged 2–4, 7–8, 12–13, and 16–20 months at various times of the estrous cycle. Hypothalamic DBH levels were low during diestrus and metestrus in all age groups. In animals aged 2-4, 7-8, and 12–13 months DBH activities started to rise on the evening of proestrus, and the highest levels attained at 21:00 h were significantly greater than those found during the morning (11:00 h) of proestrus. In contrast, in 16- to 20-month-old mice the hypothalamic DBH activity did not show any significant proestrous rise. In this age group the highest levels of DBH were present at 24:00 h, but these were not significantly different from those found at 11:00, 18:00 or 21:00 h of proestrus. Plasma LH concentrations in all age groups began to increase at 18:00 h of proestrus and had reached their highest levels by 21:00 h of proestrus. The plasma LH concentrations at 21:00 h of proestrus were significantly higher when compared with those 3 h earlier in mice aged 2–4, 7–8, and 12–13 months; however, the LH values in 16- to 20-month-old mice were not significantly different when comparing these two time periods. These data are consistent with (1) the existing idea of an increased adrenergic activity in the rodent hypothalamus during the preovulatory proestrous period and (2) the hypothesis that a dysfunctioning female reproductive system in older rodents may result from a reduction in hypothalamic catecholaminergic activity. It is suggested from the experimental results that such a reduction in adrenergic activity in the mouse hypothalamus may be, at least in part, caused by a reduction in the levels of the norepinephrine-synthesi

ISSN:0028-3835    

DOI:10.1159/000123271

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

We examined the effects and mechanisms of action of ACTH and ACTH fragments on gonadotropin secretion in immature rats. ACTH administered by daily injection or continuous infusion (osmotic minipumps) attenuated the postcastration rise in serum LH. Pituitary LH concentration was either unchanged or increased in AGTH-treated rats and pituitary sensitivity to gonadotropin-releasing hormone (GnRH) was reduced by ACTH treatment. A fragment of ACTH (ACTH 4-10), which is less steroidogenic, did not alter levels of serum LH, and ACTH did not reduce LH secretion in adrenalectomized castrates. Serum and pituitary concentrations of prolactin were normal in ACTH-treated animals. These studies demonstrate that the suppression of gonadotropin secretion by ACTH is mediated by the adrenal gland. This mechanism causes a decreased pituitary sensitivity to GnRH, but LH synthesis does not appear to be affected. Prolactin does not play a role in this mechanism.

ISSN:0028-3835    

DOI:10.1159/000123272

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

5-Hydroxytryptophan (5-HTP) was found to lower plasma 11-oxycorticoids and increase plasma growth hormone in anesthetized dogs. To determine whether these effects were mediated by release of serotonin, 5-HTP and L-tryptophan were injected intravenously alone and after treatment with various drugs. The decrease in corticoids produced by 5-HTP was unaffected by intravenous carbidopa and metergoline, but was abolished by intravenous benserazide in a dose that inhibits central 5-HTP and dopa decarboxylase, and by a small dose of phenoxybenzamine in the third ventricle. Adrenal sensitivity to ACTH was unaffected by 5-HTP. L-Tryptophan did not decrease plasma corticoids; instead it produced a small increase. The increase in plasma growth hormone produced by 5-HTP was potentiated by carbidopa and abolished by benserazide. L-Tryptophan did not increase plasma growth hormone; instead it produced no change or in some instances a decrease. Plasma growth hormone declined after administration of phenoxybenzamine in the third ventricle, and the decline continued after administration of 5-HTP. The data indicate that the effects of 5-HTP on ACTH and growth hormone secretion are not due to central release of serotonin and suggest that they are due instead to serotonin-induced release of catecholamines from catecholamine-secreting neurons.

ISSN:0028-3835    

DOI:10.1159/000123273

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Corticotropin-releasing factor (CRF) was bioassayed and arginine vasopressin (AVP) radioimmunoassayed from punched-out hypothalamic nuclei. The highest concentration of CRF was found in the median eminence (ME), followed by the paraventricular nucleus (PVN), supraoptic nucleus (SON), suprachiasmatic nucleus (SCN), arcuate nucleus (ARC), dorsomedial nucleus (DMN) and ventromedial nucleus (VMN). The AVP concentration was in the order of ME, SON, PVN, SCN, ARC, VMN and DMN. Sephadex G-25 gel filtration of the ME extracts showed one peak for AVP and two peaks for CRF. One CRF peak appeared on the void volume (big CRF) and the other (small CRF) was coeluted with AVP. Gel filtration of the PVN and SON extracts showed one peak for AVP but three or four peaks for CRF. The addition of anti-AVP serum (AVP-AS) to pituitary cell cultures reduced the CRF activities of AVP and ME extracts by approximately 80 and 40%, respectively. When the small CRF fraction of ME extracts was treated with AVP-AS on affinity chromatography, the unbound fraction (AVP-free) still showed significant CRF activity. Re-examination of CRF concentration using AVP-AS showed that it was still highest in ME, but was significantly higher in PVN than in SON, SCN and ARC. These results suggest that the PVN is an important nucleus for producing corticotropin-releasing hormone.

ISSN:0028-3835    

DOI:10.1159/000123274

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Steady-state concentrations of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) in anterior hypothalamus (AH), preoptic area (POA), suprachiasmatic nucleus (SCN), and ventromedial nucleus (VMH) were equivalent 30 days after castration or 17β (E2) or E2 + DHT for 30 days to castrated males also failed to alter differentially the concentrations of 5-HT and 5-HIAA in any of the brain regions assayed. Although castrated and sham-operated rats had similar levels of 5-HT and 5-HIAA in whole hypothalamus + preoptic area (H + POA), brain stem (BS), and cortex (CTX) when measured 7 and 32 days postoperatively, the mounting rates and the percentage of animals ejaculating were similar for both groups 6 days postoperatively whereas only the sham-operated animals continued to mount at a high rate and to ejaculate 31 days postoperatively. Also, 30 days after surgery, there were no differences among groups of males which were either castrated, castrated and given a subcutaneous capsule of testosterone, or sham operated, in the accumulation of 5-hydroxytryptophan in the H + POA, BS, or CTX measured 30 min after an intraperitoneal injection of an aromatic amino acid decarboxylase inhibitor. These results suggest that the hormonal activation of masculine sexual behavior in the rat is not mediated by a change in the metabolic activity of 5-HT neurons in either the hypothalamus or POA

ISSN:0028-3835    

DOI:10.1159/000123275

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Rat pineal cyclic AMP (cAMP) phosphodiesterases (PDEs) were studied during male development and in adult females by means of gel electrophoresis, kinetic analysis, and diurnal activity measurements. In both male and female rats, two molecular forms of PDE coexisted. In neonatal-infantile males (birth to day 20 of age) a third isozyme was detected. The kinetic properties of PDEs were essentially similar in infantile and adult male rats with respect to the Kms; however, a minimal Vmax was observed a 10.00 a.m. in adults, but not in neonatal animals. PDE activity in male rats was maximal between 2.00 a.m. and 4.00 a.m., and also at 4.00 p.m., and was minimal at 10.00 a.m. This pattern appeared to develop during the infantile period of life. The pattern of activity observed in adult female rats was similar to that of adult males, except that it lacked a pronounced afternoon peak. The diurnal PDE activity profile of castrated male adult rats was similar to female animals and testosterone substitution in male castrated rats resulted in a pattern which resembled that of adult male controls. In addition to the above measurements, testosterone serum levels have been determined during all of these experiments.

ISSN:0028-3835    

DOI:10.1159/000123276

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Prolactin-releasing (PRF) activity was found in Pitressin® (a commercial extract from posterior pituitary for vasopressin). Injection of Pitressin into conscious free-moving rats implanted with a permanent atrial indwelling cannula, produced a transient increase in prolactin concentration in the circulation. In order to find out whether the PRF activity was due to vasopressin or to an unidentified component in the Pitressin, we tested synthetic lysine vasopressin and demonstrated that vasopressin (1 U/kg) elevated plasma prolactin concentration about threefold. In contrast, oxytocin (1 U/kg) did not alter the prolactin concentration. In order to find out whether the effect of vasopressin is a direct or indirect action, we tested the vasopressin effect on hypophysectomized rats which had previously been implanted with 2 adenohypophyses under the kidney capsule. Again this dose (1 U/kg) of vasopressin elevated circulating plasma prolactin. These experiments indicate that vasopressin can elevate circulating prolactin concentration in nonestrogen-primed normal male rats and that vasopressin also stimulates prolactin secretion from transplanted glands dissociated from direct hypothalamic control

ISSN:0028-3835    

DOI:10.1159/000123277

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Cerebrospinal fluid (CSF) obtained from the cisterna magna of conscious unrestrained guinea-pigs was assayed for oxytocin (OT), vasopressin (AVP) and neurophysin (NP). Basal levels of OT and AVP were approximately 5 and 15 fmol/ml, respectively, whereas NP levels were considerably higher (around 1 pmol/ml); there were no significant differences between males, females and lactating females. In lactating females, simultaneous samples of blood and CSF were obtained during suckling episodes. Despite large increases in plasma OT and NP at milk ejection, CSF levels remained unchanged throughout. Intracerebro ventricular injection of 100 fmol OT produced an 8-fold rise in the concentration of this peptide in cisternal fluid within 10 min. Since CSF levels of OT and NP do not change when these peptides are released from the pituitary, we conclude that the presence of these peptides in CSF reflects activity of extrapituitary terminals and that these terminals are not activated during suckling.

ISSN:0028-3835    

DOI:10.1159/000123278

出版商:S. Karger AG    

年代:1982

数据来源: Karger