摘要:

The effects of coronal knife cuts posterior to the organum vasculosum of the lamina terminahs on pressor responses to intraventricular (i.v.t.) and intravenous (i.v.) angiotensin II (AII), i.v.t. hypertonic NaCl and i.v. norepinephrine were tested in the rat. Drinking responses to i.v.t AII were also measured. Knife cuts attenuated the blood pressure responses to i.v.t and i.v. AII, but not to i.v.t. hypertonic NaCl and i.v. norepinephrine. Drinking responses to i.v.t. AII were not reduced. These data indicate that neural pathways which mediate the pressor response to i.v.t. AII pass through this portion of the hypothalamus and are distinct from the neural pathways which mediate drinking to central AII.

ISSN:0028-3835    

DOI:10.1159/000123346

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

In this study changes in serum FSH concentration, hypothalamic LHRH content and in vitro release of LHRH from hypothalami of female Wistar rats during prepubertal development are described. The concentration of FSH in serum was determined by radioimmunoassay. Extremely high levels (1.800 ng/ml) were found between 12 and 16 days of age. Thereafter, FSH levels rapidly fell to low levels (135 ng/ml) on day 32. LHRH was measured by radioimmunoassay in extracts of mediobasal hypothalami (MBH) and showed a gradual increase during the first 10 days of life. Between 10 and 16 days of age, hypothalamic LHRH content did not change. After day 16, LHRH content sharply increased to a maximum found on day 32. The release of LHRH from MBH of developing rats was studied during in vitro incubation in Krebs-Ringer bicarbonate buffer. LHRH in the medium was measured by radioimmunoassay. The spontaneous release rate of LHRH was maximal from MBH of 12-day-old rats and minimal from those of 32 days. Depolarization of neural membranes, by medium containing 45 mM K+ induced a stimulation of LHRH release. This K+-induced release of LHRH was also most prominent on day 12. These observations are consistent with the hypothesis that the high circulating FSH levels found in female rats between 12 and 16 days of age are at least in part caused by a high secretion rate of LHRH during this period.

ISSN:0028-3835    

DOI:10.1159/000123347

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

A specific and sensitive homologous radioimmunoassay (RIA) for determination of hamster prolactin is described and compared to heterologous hamster prolactin RIA and to the homologous and heterologous RIAs for rat prolactin. With this method, we have determined that, in the golden hamster, diurnal plasma prolactin fluctuations have a mean interpeak interval of 1.5 h, that serum prolactin concentrations are influenced by day length, by ether vapors, by animal’s gender, and by refeeding following a fast but not by neurosurgical procedures which increase somatic growth and serum GH concentration in adult hamsters. Variations in day length influenced pituitary prolactin content and concentration, and pituitary removal abolished prolactin secretory responses to ether stress. A heterologous RIA for hamster prolactin which utilizes radioiodinated rat prolactin and rabbit antihamster prolactin serum (RK1–15) represents the most advantageous method for the measurement of hamster prolactin because of its high sensitivity (0.14 ng/ml), high antiserum binding to iodinated rat prolactin, and the ability to measure both hamster and rat prolac

ISSN:0028-3835    

DOI:10.1159/000123348

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The experiments were designed to investigate the possible role of ovarian hormones in causing increased synthesis by neurones of the supraoptic (SO) and paraventricular (PV) nuclei previously found during pregnancy and lactation. Changes in the dry mass of nucleoli of these neurones were measured to indicate their synthetic activity. When a normal suckling stimulus was applied only after a delay of 7 days post-partum the nucleolar changes in PV and SO neurones that followed were similar to those that occur normally when a litter is suckled from birth; these changes thus do not depend on the hormonal state of late pregnancy or early lactation. After unilateral nipple line ablation prior to pregnancy nucleolar dry mass of PV and SO neurones increased bilaterally in a subsequent lactation. These results do not distinguish bilateral distribution of the milk ejection pathway from the action of hormones on PV and SO neurones. Nucleoli of SO and PV neurones in virgin rats were larger after treatment with a large dose of oestradiol for 5 days, but were not affected by ovariectomy, progesterone treatment or by the stage of the oestrous cycle. It is concluded that increased synthetic activity in SO and PV neurones during lactation depends upon the suckling stimulus rather than on changes in secretion rates of ovarian hormones; oestradiol may cause the nucleolar changes in PV and SO neurones seen at the end of pregnancy.

ISSN:0028-3835    

DOI:10.1159/000123349

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

Methionine-enkephalin (met-enk) levels were measured at 09.30–10.30, 16.30–17.30 and 23.30–00.30 h in the anterior hypothalamus-preoptic area (AHPOA), medial basal hypothalamus (MBH), anterior, intermediate and posterior lobe of the pituitary gland of male rats. Met-enk levels in the AHPOA and MBH fluctuated significantly through a 24-hour period; from low levels at 09.30–10.30 h, met-enk in the AHPOA and MBH rose slowly in the afternoon to reach peak concentrations at 23.30–00.30 h. Pinealectomy appears to depress or shift the normally occurring increments in met-enk levels at 23.30–00.30 h in the AHPOA only. Serum testosterone (T) levels displayed an inverse relationship with the met-enk rhythm; high concentrations during the day were associated with low met-enk levels and as T levels decreased to a nadir at 23.30–00.30 h, the met-enk in the MBH and AHPOA attained peak concentrations. Daily changes in serum T levels were not affected by

ISSN:0028-3835    

DOI:10.1159/000123350

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

A number of centrally active benzodiazepines lowered baseline serum prolactin concentrations after oral administration to male rats. The increase of circulating prolactin levels elicited by oral administration of various neuroleptic agents was also reduced by prior or simultaneous oral administration of several benzodiazepines in a dose-dependent manner. Since both effects were prevented by simultaneous administration of the benzodiazepine antagonist Ro 15-1788 they are probably mediated by central benzodiazepine receptors which interfere with aminergic mechanisms governing serum prolactin.

ISSN:0028-3835    

DOI:10.1159/000123351

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The purpose of this study was to determine if the temporal relationship between the LH surge and the photo-period is influenced by melatonin and the pineal gland in the rat. The timing of melatonin synthesis and of preovulatory LH release is reciprocally related; and since melatonin blocks LH secretion, it was hypothesized that the pineal ‘hormone’ contributes normally to termination of the LH surge. To test this hypothesis, we examined the temporal pattern of phasic LH secretion after altering pineal activity in rats with regular estrous cycles. Termination of the LH surge was delayed in rats exposed to a photophase acutely prolonged into the night of proestrus; a treatment which delays melatonin synthesis. On the other hand, the LH surge terminated normally despite extended light exposure, if the rats were injected with melatonin at 19.00 h, when the dark phase usually begins. Melatonin injections during the standard photophase, i.e. at 13.00 or 17.00 h, blocked or prematurely terminated the LH surge, respectively. However, these effects probably do not represent a physiological function of melatonin, since its synthesis does not accelerate normally until after dark. 5 out of 14 pinealectomized rats showed altered patterns of preovulatory LH secretion 2 months after surgery. Since melatonin has been reported to block serotonin receptors, and serotonin stimulates phasic secretion of LH, we tested the ability of quipazine, a serotonin receptor agonist, to antagonize the inhibitory effect of melatonin on the LH surge. Quipazine given at 15.30 h blocked the inhibitory effect of melatonin administered at 16.00 h. The serotonin agonist partially restored LH levels in proestrous rats when it was given 30 min after melatonin. Therefore, the inhibitory effect of melatonin on phasic secretion of LH may result from an action upon serotonin-containing neurons. These findings taken together suggest that the pineal gland, ostensibly through the action of melatonin, contributes to termination of phasic LH secretion and thereby participates in entrainment of the LH surge to the photoperiod in the female

ISSN:0028-3835    

DOI:10.1159/000123352

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The effects of histamine and amodiaquine (a drug known to inhibit histamine-N-methyltransferase) on pulsatile growth hormone (GH) secretion were determined in unanaesthetized male rats. Intracerebroventricular (i.c.v.) administration of histamine (0.01, 0.05, 0.1 μmol/rat) caused a dose-related suppression of spontaneous pulses of rat GH (rGH) secretion. Amodiaquine (0.16 μmol/rat i.c.v.) also inhibited the pulses, but to a lesser degree. The results, which show the inhibitory effects of both exogenous histamine and increased levels of endogenous histamine on pulsatile rGH secretion, support the hypothesis that the histaminergic system also plays a role in physiological CNS control of rGH secretio

ISSN:0028-3835    

DOI:10.1159/000123353

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

To investigate the effects of norepinephrine (NE) on LH secretion, when given into different hypothalamic and extrahypothalamic brain regions, we microinjected 1 μl of NE in dosages of 10–4M concentrations, 10–6, 10–8 and 10–10 M into nine different brain areas in ovariectomized miniature pigs. Microinjections into the dorsal hypothalamus (ADH) and dorsomedial nucleus (DM) had dose-dependent effects. The higher dose of NE (10^6 M) inhibited and the lower dose of NE (10–10 M) stimulated LH secretion, when NE was microinjected into the ADH (n = 4 – number of animals). Microinjections into the DM (n = 6) had the opposite effect. Here the lower dose had inhibitory and the higher dose stimulatory effects on plasma LH levels. Microinjections into the ventromedial nucleus of the hypothalamus (n = 4) had no significant effect. Microinjections into the stria terminalis (n = 3) and zona incerta (n = 4) were also ineffective. The effect of NE microinjections into the subthalamic nucleus (n = 4) resembled responses to microinjections into the ADH. NE effects in the amygdala were not dose dependent. Microinjections into the basolateral amygdala (n = 5) decreased and microinjections into the corticomedial part of the amygdala (n = 5) increased plasma LH levels in all four doses of NE. The effects of NE micro-injected into the hippocampus (n = 3) were not clear cut. These results indicate a dualism of NE on LH secretion. Thus, the predominant notion that NE is largely or even exclusively stimulatory to LH release should be revised. According to the previous findings and the results of the present study it has been concluded that the effects of NE on LH secretion are not only dependent on the hormonal status of the animal, but also to the dose and site of

ISSN:0028-3835    

DOI:10.1159/000123354

出版商:S. Karger AG    

年代:1982

数据来源: Karger

摘要:

The effects of adrenergic stimulation on the pulsatile release of LH were investigated in ovariectomized rats with acute depletion of brain norepinephrine (NE) levels. Rats bearing atrial cannula were pretreated with NE synthesis inhibitors, diethyldithiocarbamate (DDC) or bis (4-methyl-1-homopiperanzinyl thiocarbanyl) disulfide (FLA-63) and blood was withdrawn at 15-min intervals beginning 1 h later. DDC and FLA-63 markedly dampened pulsatile LH secretion. Administration of the α-adrenergic agonist clonidine (CLON) resulted in immediate LH release and apparent resumption of pulsatile LH secretion. The facilitatory effect of CLON on LH secretion was more pronounced in FLA-63 than in DDC-pretreated rats. Additional characterization of the pattern of LH secretion in FLA-63-pretreated rats showed that the interval between LH pulses was significantly lengthened after acute NE depletion; however, CLON treatment increased LH pulse frequency to that found in ovariectomized rats. To further investigate the ability of CLON to augment pulsatile LH release, the LH secretory pattern was determined between 2 and 4 h after CLON administration in FLA-63-pretreated rats. 8 of 10 rats receiving CLON (0.3 mg/kg) responded with episodic LH release 2–4 h following treatment while saline-treated rats continued to show dampened LH secretory patterns. These studies demonstrate that following acute depletion of NE in ovariectomized rats, a single injection of CLON can enhance both the amplitude and frequency of LH pulses. Further, the data suggest that central noradrenergic neurons exert only a permissive effect on pulsatile LH release and that the pulsatile mechanism may predominately be resident in LHRH neuro

ISSN:0028-3835    

DOI:10.1159/000123355

出版商:S. Karger AG    

年代:1982

数据来源: Karger