摘要:

2 µg dopamine (DA) were injected into particular hypothalamic sites containing dopaminergic nerve terminals, on the morning of pro-oestrus in cyclic rats, in which ovulation was blocked by administration of 35 mg/kg pento-barbitone Na, in the afternoon of pro-oestrus. DA in a specific area of the zona incerta (ZI) (medial area at A 5.4 mm; de Groot atlas), and medial anterior hypothalamus (AH) overcame the pentobarbitone block and induced ovulation. Injections into the median eminence and preoptic area were ineffective, as were injections of 5-hydroxytryptamine and noradrenaline into the ZI. Injection of 2 µg haloperidol and lesions in the ZI inhibited ovulation in otherwise untreated cyclic rats. Lesions induced constant dioestrus for 14 ± 0.7 days, but the animals were not pseudopregnant. 2 µg DA were also injected into the ZI of ovariectomised rats primed with 2 µg oestradiol benzoate 48 h before; this treatment stimulated a rise in plasma LH approximately 40 min later. These findings indicate that the dopaminergic incerto-hypothalamic tract which has nerve terminals in the ZI and AH has a stimulatory role in the control of gonadotrophin rel

ISSN:0028-3835    

DOI:10.1159/000123995

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

8–10 days after making various lesions in the rat hypothalamus, the presence of corticotropin releasing factor (CRF) immunoreactive neural structures was studied in paraffin and vibratome sections with CRF immunocytochemistry. (1) Bilateral anterolateral deafferentation of the medial basal hypothalamus (MBH) caused complete disappearance of CRF immunoreactivity from the median eminence (ME) in brains where the posterior edge of the cut reached the level of the pituitary stalk. A shorter cut resulted in positive immunostaining caudal to the caudal edge of the cut. (2) Unilateral deafferentation of the MBH caused significant decrease in CRF immunostaining in the ipsilateral ME. (3) Unilateral posterolateral deafferentation of the MBH caused no changes in CRF immunostaining in the rostral ME, while fewer CRF-containing processes were observed in the more caudal regions. (4) A horizontal cut ventral to the paraventricular nuclei (PVN) caused a slight decrease in the number of CRF-immunoreactive profiles in the ME. A wider and complete unilateral horizontal cut resulted in a significant decrease in CRF immunoreactivity on the operated side. Following various surgical interventions, hormone accumulation in cell bodies was detected in the paraventricular, periventricular preoptic, dorsomedial, periventricular, lateral and posterior hypothalamic, and premammillary nuclei. Fibers arising from most of these nuclei formed a fan-like projection to the ME. The majority of the CRF-fibers ran through the lateral tract of the fan, and reached the ME by the lateral-basal retrochiasmatic area (LBRCA). Scattered fibers were detected in the lateral-basal hypothalamus as far caudally as the level of the pituitary stalk. Unilateral anterolateral and horizontal cuts did not result in complete disappearance of CRF immunoreactivity from the ipsilateral ME, indicating the existence of CRF-fibers of contralateral origin in the M

ISSN:0028-3835    

DOI:10.1159/000123996

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

We administered crystalline melatonin (80 mg) in gelatin capsules to 5 young male volunteers and measured serum and urinary melatonin levels at intervals. Changes in serum melatonin levels were best described by a biexponential equation with an absorption constant (ka) of 1.72 h-1 (half-life = 0.40 h) and an elimination constant (kel) of 0.87 h-1 (half-life = 0.80 h). Peak serum melatonin levels, ranging from 350 to 10,000 times those occurring physiologically at nighttime, were observed 60–150 min after its administration, remaining stable for approximately 1.5 h. The fraction of ingested melatonin that was absorbed, estimated from the area under the curve describing serum melatonin concentrations as a function of time after melatonin administration (the concentration-time curve), varied by 25-fold among subjects. 3 additional volunteers received three melatonin-containing capsules (80 mg each) at 60-min intervals. This regimen extended the duration of elevated serum melatonin levels to 4–6 h. Melatonin excretion closely paralleled serum melatonin levels until 9 h after the hormone’s administration, after which urinary levels tended to be higher than those predicted from serum levels. However, the area under the concentration-time curve for serum melatonin correlated well (r = 0.96) with the cumulative melatonin excretion during the initial 15 h after melatonin’s administration, indicating that either approach can be used to estimate the absorption of orally administered me

ISSN:0028-3835    

DOI:10.1159/000123997

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Plasma concentrations of growth hormone (GH) were elevated in anaesthetized male domestic fowl following the intravenous administration of either synthetic human pancreatic GH-releasing factor 1–44 (NH2) (hpGRF) or synthetic thyrotrophin-releasing hormone (TRH). In 6-week-old chicks the plasma GH level was elevated between 5 and 10 min after the injection of hpGRF at doses between 1 and 80 µg/kg. The magnitude of the response increased with doses of hpGRF between 1 and 10 µg/kg but declined with higher doses. The GH concentration rapidly declined between 10 and 20 min and between 20 and 40 min after injection. The administration of TRH had similar effects on GH secretion, although the responses were greater than with comparable doses of hpGRF, and the most effective dose (1–1.4 µg/kg) was less than with hpGRF. In anaesthetized adult cockerels GH secretion was also increased by the administration of hpGRF (1–20 µg/kg) or TRH (0.1–80 µg/kg) and in both cases the dose-response relationship was biphasic. The maximal response to TRH in adult birds was again greater than that produced by hpGRF although the response was less than that elicited in immature birds and required a higher dose (20 µg/kg) of TRH. The optimal dose of hpGRF and the magnitude of the GH response induced in adult birds was comparable with that in immature chicks. These results demonstrate provocative effects of TRH and hpGRF on GH secretion in the domestic fowl. The sensitivity of the GH response to TRH suggests that it may have a physiological role in the hypothalamic control of

ISSN:0028-3835    

DOI:10.1159/000123998

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Studies were undertaken to evaluate the effects of chronic hyperprolactinemia (HYP) induced by the MtTWI5 tumor on the thermoregulatory response of female rats to blockade of opiate receptors with naloxone. Both chronic administration of morphine and HYP cause a mild hyperthermia as evidenced by a 0.8–1.0 °C elevation in rectal temperature (Tr). Naloxone-precipitated morphine withdrawal caused a prompt increase (4.9 ± 0.76 °C) in tail skin temperature (TST) and a subsequent decline in Tr (-2.8 °C). Similarly, naloxone administration to HYP rats caused a dramatic TST response which was coincident with the onset of severe HYP. This effect of naloxone was maximal at 7 weeks of tumor growth when a TST response of 4.8 ± 0.3 °C was observed but was not evident prior to or 1 week following tumor inoculation, when serum prolactin levels were low. The TST response to naloxone in chronic HYP exhibited distinct pulses with an amplitude of 3.4 ± 0.4 °C and a frequency of 2.2 ± 0.5 pulses per 120 min. It appears that blockade of opiate receptors in HYP rats induces instability in the regulation of skin temperature as evident by recurrent episodes of TST surges. These effects of chronic HYP on the TST response to naloxone were not influenced by ovariectomy, suggesting that changes in ovarian secretions were not involved in the response. At 4 weeks of tumor growth, immunoreacitve β-endorphin concentrations in the medial basal hypothalamus, preoptic area-anterior hypothalamus and the neurointermediate lobe of the pituitary were decreased by 59, 28 and 47%, respectively. Anterior pituitary concentration of immunoreactive β-endorphin were not significantly altered at this time. Collectively, these data indicate that (1) HYP can induce alterations in core body temperature and skin temperature responses to naloxone which are similar to those observed in morphine-dependent rats; (2) chronic HYP causes depletion of imunoreactive β-endorphin in the hypothalamus and the neurointermediate lobe of the pituitary, and (3) chronic HYP max exert these effects by an action on β-endorphin cont

ISSN:0028-3835    

DOI:10.1159/000123999

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The effect of two different population densities (3 and 9 animals/cage) on emotional reactivity, measured by their performance in an exploratory box, and pituitary-adrenal response to acute noise stress are compared. The crowded rats showed a higher defecation rate and lower exploratory activity than the control rats. Adrenocorticotropin (ACTH) response to noise was higher in the crowded than in the control rats. The results clearly indicate that crowding increased emotional reactivity in adult male rats.

ISSN:0028-3835    

DOI:10.1159/000124000

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

This study was performed to examine an involvement of adenohypophysial arachidonic acid metabolites in the local mechanisms controlling the release of peptide hormones from the corticotrope cells of the anterior pituitary gland. Therefore, we investigated the effect of blockers of the lipoxygenase (nordihydroguaiaretic acid, NDGA), cyclooxygenase (indomethacin) or both of these enzyme systems (BW755C; eicosatetraynoic acid, ETYA) on the release of β-endorphin-like (β-E-IR) and adrenocorticotropin-like immunoreactivity (ACTH-IR) from rat anterior pituitary quarters incubated in vitro.NDGA and ETYA did not influence the basal release of β-E- and ACTH-IR. However, upon stimulation by arginine-vasopressin (AVP) or synthetic ovine corticotropin-releasing factor (CRF(i_4i)), NDGA inhibited β-E-IR release by 40%. ETYA inhibited AVP-induced release of β-E- and ACTH-IR by 75%. Indomethacin and BW755C (lower concentration) enhanced β-E-IR release, induced by AVP, by about 100%, whereas BW755C (higher concentration) had no effect. When indomethacin was present, NDGA, ETYA and BW755C (higher concentration) inhibited AVP-induced release of β-E- and ACTH-IR. Prostaglandin E2 (PGE2) inhibited β-E-IR release in response to AVP but failed to do so in the presence of NDGA. 12-OH-5,8,10,14-eicosatetraenoic acid (12-HETE) had no effect. When anterior pituitary quarters were incubated with 3H-arachidonic acid (3H-AA), NDGA and BW755C (higher concentration) but not indomethacin and BW755C (lower concentration) blocked the formation of a metabolite which co-migrated with 12-HETE on thin-layer chromatography. We conclude that stimulus-induced release of β-endorphin and ACTH from the adenohypophysis is closely coupled with oxidized arachidonic acid metabolites; dual pathways of arachidonic acid metabolism may participate and have opposing regulatory effects: an inhibitory cyclooxygenase cascade and a stimulatory cascade possibly via the lipo

ISSN:0028-3835    

DOI:10.1159/000124001

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Male rats were treated for 14 days with dexamethasone (2.6 µmol/l in the drinking water) and killed at various times after withdrawal of the drug. Some animals were subjected to stress (ether or sham adrenalectomy) just before killing. The recovery of responsiveness of the components of the hypothalamo-pituitary-adrenocortical axis was assessed by measuring plasma and tissue concentrations of hormones, and the response of the tissue in vitro to appropriate stimuli. In vitro, bioactive corticotrophin-releasing factor (CRF) release in response to acetylcholine and adrenal corticosterone release in response to adrenocorticotrophin (ACTH) were significantly suppressed until 3 days after withdrawal. However, release of immunoreactive or bioactive ACTH in response to ovine CRF or hypothalamic extract did not return to normal until day 5. This was correlated with a reduction in pituitary immunoreactive ACTH content and bioactive plasma ACTH, which were suppressed until days 5 and 4, respectively. No change in hypothalamic immunoreactive CRF content could be detected after treatment, or after stress (ether or sham adrenalectomy) in either treated or control animals. Stress (ether) had no effect on the subsequent response of the anterior pituitary gland in vitro to ovine CRF. The large rises in plasma ACTH and adrenal corticosterone measured after stress (ether) in control animals were completely abolished after dexamethasone treatment and did not return to control values until 5 days after withdrawal. Therefore, it appears that after cessation of chronic dexamethasone treatment in the rat, the responsiveness of the hypothalamus and adrenal gland return to normal before that of the pituitary gland

ISSN:0028-3835    

DOI:10.1159/000124002

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

The cardiovascular and vasopressin-releasing effects of vertebral artery, carotid artery and intravenous (i.v.) infusions of lysine vasopressin (150 µU/kg·min) were studied in anesthetized dogs. Vertebral and carotid artery infusions of lysine vasopressin led to similar decreases in cardiac output as i.v. infusions. Heart rate, however, decreased to a greater extent with vertebral and carotid artery infusions of lysine vasopressin than i.v. infusions. There were no changes in either mean arterial blood pressure or the plasma vasopressin concentration. The results indicate that peripheral vasopressin: (1 has a central effect to reduce heart rate; (2) has a peripheral effect on the heart to reduce cardiac output, and (3) probably does not feed back to inhibit its own releas

ISSN:0028-3835    

DOI:10.1159/000124003

出版商:S. Karger AG    

年代:1984

数据来源: Karger

摘要:

Pineal serotonin and melatonin levels and the activities of hydroxyindole-0-rnethyltransferase (HIOMT) and N-acetyltransferase (NAT) were studied over a 24-hour period in the pineal gland of the diurnally active Richardson’s ground squirrel (Spermophilus richardsonii). Under alternating light-dark conditions (light:dark hours 14:10), pineal serotonin and melatonin levels exhibited a rhythm with high values occurring either during the day (serotonin) or during the night (melatonin). NAT activity was also markedly increased during darkness. HIOMT activity exhibited no 24-hour variation. Exposure of squirrels to constant light for 7 days exaggerated the serotonin rhythm, but obliterated the cycles of NAT and melatonin. Under constant darkness (for 7 days), the rhythms in serotonin, melatonin and NAT persisted, each having a period of about 24 h. In the second study, ground squirrels were exposed to light-dark cycles of either 8:16, 10:14 or 14:10. Under each of these photoperiodic environments, rhythms in pineal NAT and melatonin were apparent. Increasing the daily dark period from 10 to 14 h caused a prolongation of the elevated NAT and melatonin levels. However, a further prolongation of the daily dark period (to 16 h) did not further increase the duration of the rise in NAT and melatonin. The results show that continual light exposure (irradiance of 200 µW/cm2) for 7 days suppresses the pineal rhythms in both NAT activity and melatonin level in the Richardson’s ground squirrel. Conversely, light exposure, rather than depressing the serotonin rhythm, actually exaggerates it. Constant darkness for 7 days has little influence on the 24-hour rhythms of either NAT or melatonin. In the Richardson’s ground squirrel, it appears that the quantity of melatonin formed may be in part related to the duration of the daily dark

ISSN:0028-3835    

DOI:10.1159/000124004

出版商:S. Karger AG    

年代:1984

数据来源: Karger