摘要:

Electrical stimulation of the neural lobe (NL) of the pituitary induces a rise in plasma corticosterone indicating the release of adrenocorticotropin (ACTH) in rats pretreated with dexamethasone, morphine and pentobarbitone. 7–8 days after placing an anterolateral cut around the medial basal hypothalamus (MBH), the rats failed to respond with ACTH release to electrical stimulation of the NL; the number of nerve fibers and terminals in the NL decreased to less than 5% of the normal; and ACTH releasing activity of acid extracts of the NL was undetectable using both in vivo and in vitro tests, which are insensitive to vasopressin. After lesions of the paraventricular nuclei the stimulation of the NL elicited a rise of plasma corticosterone that was significantly less than that in the controls. These results suggest that the NL of the pituitary contains electrically excitable fibers capable of releasing corticotropin-releasing factor (CRF; distinct from vasopressin) and that these fibers probably originate from outside the MBH, witha portion of them coming from or through the paraventricular nuclei or their immediate vicinit

ISSN:0028-3835    

DOI:10.1159/000123081

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Fresh pineal explants were cultured in medium 199 containing 0.1 mg/ml of ascorbic acid, 2 mM glutamine, and 0.1% BSA in 95% O2 and 5% CO2 from 1 to 10 h. Norepinephrine (10 µM) increased serotonin N-acetyltransferase (NAT) activity from 2.36 ± 0.23 to 6.98 ± 0.46 pmol product produced/mg protein/min (unit), without influencing tryptophan hydroxylase, 5-hydroxytryptophan decarboxylase, monoamine oxidase, or hydroxyindole-O-methyltrans-ferase. Dibutyryl cyclic AMP (1 mM) also stimulated NAT from 1.39 ±0.12 to 4.33 ±0.65 U. The norepinephrine-induced stimulation of NAT was blocked by GABA (10 µM), by dl-propranolol (20 µM), by cycloheximide (30 µM), by puromycin (20 µM), but not by actinomycin D (10 µM). Comparing the kinetics of native and stimulated NAT, there occurred changes in Vmax with regard to both substrates – tryptamine (from 0.885 to 3.44 U) and acetyl CoA (from 3.45 to 9.10 U) – without changes in Km with respect to both tryptamine (Km = 5 µM) and acetyl CoA (Km = 50 µM). The results of this investigation are interpreted to indicate that the norepinephrine-induced stimulation of NAT may be due to enhanced protein synthesis involving translational or post-translational events. Furthermore, the enhanced protein synthesis is coupled through activation of β-receptor and cyclic AMP mediated actions in pineal gland. The precise interrelationship between GABA and norepinephrine in mediating and perhaps in controlling the biological events in the bovine pineal gland still awai

ISSN:0028-3835    

DOI:10.1159/000123082

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Aging is associated with alterations in mood, thermoregulation, pain threshold, and stress response. Because these functions may be modulated by endogenous opiates, we measured immunoreactive ACTH and β-endorphin in discrete brain areas and pituitary glands from rats aged 6 weeks (young), 6 months (mature), and 20–24 months (senescent). β-Endorphin and ACTH declined significantly with aging in the hypothalamus and corpus striatum. β-Endorphin and ACTH increased in the frontal lobe during early life; however, no change was noted after maturity. A discordant response with age was noted in the pituitary in that ACTH did not change, while β-endorphin increased early in life without change after maturity. Cerebellar tissue exhibited no immunoreactive ACTH or β-endorphin. Age-related changes in brain and pituitary β-endorphin and ACTH must be considered in the evaluation of the physiological aging process and when comparing studies of these neurop

ISSN:0028-3835    

DOI:10.1159/000123083

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The possibility that serotonin plays a role in prolactin secretion after electrical stimulation of the rhesus medial basal hypothalamus (MBH) was investigated. Prolactin responses to electrical stimulation and intravenous injection of 0.5 and 1.0 µg of thyrotropin-releasing hormone (TRH) were evaluated before and after administration of methysergide (MES), a serotonin receptor blocker (2 mg orally every 12 h for 48 h), and bromocriptine (CB-154), a dopamine agonist (2.5 mg orally every 12 h for 48 h). Both electrical stimulation and TRH caused prompt increases in serum prolactin. Prestimulation (basal) prolactin levels in both drug-treated groups were not significantly lower than basal levels in control groups. Pretreatment with MES significantly attenuated the electrically induced release of prolactin but had no effect on the TRH-induced release; CB-154 blocked prolactin release induced by both types of stimulation. The study reported here has provided evidence of a possible role for hypothalamic serotonin in releasing pituitary prolactin

ISSN:0028-3835    

DOI:10.1159/000123084

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

In diabetes insipidus (DI) rats, electrical stimulation of the posterior pituitary lobes in vitro promotes the release of corticotropin-releasing factor (CRF). The CRF activity is abolished by preincubation of the posterior lobe media with thioglycolate. Oxytocin, which is released concomitantly into the medium (3.2 mIU/lobe/20 min), accounts for the complete CRF effect. Neural lobe extracts from DI and normal rats contain 40–70% more CRF activity than can be explained by their content in vasopressin and/or oxytocin. The discrepancy between released and extracted CRFs suggests that hypothetical CRFs or potentiating factors are not released from nerve endings or have to be present in high concentrations to manifest their effec

ISSN:0028-3835    

DOI:10.1159/000123085

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Testosterone was administered to female rats in high (1.25 mg) and low (10 µg) doses at different stages of development to determine if the well-known changes in reproductive function following such treatment are accompanied by altered serotonin metabolism in the pineal gland. Testosterone (1.25 mg) given on day 3 of life depressed pineal serotonin levels and abolished pineal serotonin circadian rhythm at 7, 20 and 60 days of age. A comparable dose of testosterone given on day 13 depressed the serotonin rhythm at day 20, but the rhythm was restored at day 60. 60-day-old rats which received testosterone (1.25 mg) on day 13 showed regular estrous cycles, while the neonatally treated rats were acyclic. Therefore, the sterilizing effect of testosterone also prevented development of daily pineal serotonin rhythms

ISSN:0028-3835    

DOI:10.1159/000123086

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The differences in plasma prolactin concentration between normal and estradiol-implanted male rats were compared after treatment with 3 different stimulating agents of prolactin secretion [ether anesthesia, pimozide (a ‘specific’ dopaminergic receptor blocking agent) and TRH] using conscious, free-moving rats implanted with permanent intra-atrial cannulae. It has recently been shown that ether stress raises the circulating prolactin concentration by stimulating PRF secretion. The ether stress elevated prolactin concentration from 100 to 400 ng/ml in the estradiol-implanted rat and from 10 to 40 ng/ml in the normal male. Thus, the ether stress elevated the prolactin concentration 4 times over the basal level in both normal male and estradiol-implanted male rats, implying that the physiological role of the PRF is not changed by the estradiol implantation. A bolus injection of pimozide (1 mg/kg) elevated the plasma prolactin concentration in both the normal and estradiol-implanted male with an initial surge followed by descent to a maintained plateau level. This plateau level in the estradiol-primed rat was 600 ng/ml and in the nonprimed male rat, 50 ng/ml. The ratio of the plateau concentration over the basal level was 4 times for both groups, suggesting that the physiological role of the PIF in the estradiol-implanted rat is not different from that in the normal male rat. It is known that TRH not only stimulates TSH secretion but will stimulate prolactin secretion as well. A very large dose (0.6 mg/kg) of TRH elevated prolactin concentration 6-fold in the estradiol-implanted rat but stimulate little prolactin secretion in the normal male rat. Since ether exposure appears to stimulate prolactin secretion in both estradiol-primed and non-primed male rats through PRF secretion, while TRH was not able to stimulate a significant amount of prolactin secretion in the normal male rat, we concluded that TRH acts to stimulate prolactin secretion in estradiol-primed rats but through a different mechanism than that operating for

ISSN:0028-3835    

DOI:10.1159/000123087

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

In the anesthetized, normally hydrated dog, the i. v. infusion of norepinephrine (NE; 0.5 µg/kg/min) resulted in an increased blood pressure and a marked reduction in the plasma vasopressin (ADH) concentration (2.6 ± 0.2 to 1.1 ± 0.2 µU/ml). Urine flow and osmolar clearance increased, and urine osmolality fell. However, the negative free water clearance (TCH2O) increased, despite the reduction in plasma ADH levels. Thus, the NE-induced diuresis appeared to be due largely to the increased solute excretion, but the reduction in plasma ADH levels may also have been a factor. These data show that change in free water clearance is not a satisfactory index of change in the plasma ADH concentration when there are acute changes in renal hemodynamics and solute excretion. The norepinephrine-induced reduction in ADH secretion appeared to be due largely to increased activity of the arterial baroreceptors, but a central action cannot be ruled

ISSN:0028-3835    

DOI:10.1159/000123088

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effect of vasoactive intestinal peptide (VIP) on the release of prolactin (PRL), gonadotropins (LH and FSH), growth hormone (GH) and corticotropin (ACTH) was studied using purified rat anterior pituitary cells obtained by means of velocity sedimentation at unit gravity. VIP, at concentrations ranging from 10–10 to 10–7M, stimulated PRL secretion in a dose-dependent manner with an ED50 of 2 nM and a maximal response of 530% of control values. In contrast, similar concentrations of VIP did not affect the release of either LH, FSH, GH or ACTH from the corresponding enriched cell populations. Addition of dexamethasone (10–9M) to both preincubation and incubation medium of PRL cells completely inhibited VIP-induced PRL release. The present results further support the hypothesis that VIP is of physiological importance in the control of PRL secretion and demonstrate that corticosteroids can modify the responsiveness of PRL cells t

ISSN:0028-3835    

DOI:10.1159/000123089

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The effect of castration and adrenalectomy was studied on vasoactive intestinal peptide (VIP) concentrations in various brain and peripheral structures of male rats. Castration has no effect on any of the structures studied, whereas 4 weeks adrenalectomy (ADX) decreases VIP concentrations in the hippocampus and increases them in the adenohypophysis, two structures known to contain large amounts of glucocorticoid receptors. Corticosterone administration restores VIP levels to control values only in the dorsal hippocampus. In contrast, dexamethasone counteracts both the decrease and the increase of VIP concentrations obtained after ADX in the hippocampus and in the adenohypophysis respectively. The present results suggest that corticosteroids can be involved in the regulation of VIP actions both in the brain and in the adenohypophysis.

ISSN:0028-3835    

DOI:10.1159/000123090

出版商:S. Karger AG    

年代:1980

数据来源: Karger