摘要:

Catheterization of the femoral artery using rubber band restraint markedly lowered growth hormone (GH) levels in plasma of male rats which had been anesthetized with pentobarbital (PB). Other stressful factors existing in the process of catheterization, such as skin incision, soft tissue separation to expose the femoral artery, restraint on the back, catheterization with scotch tape restraint and catheterization without restraint, did not produce a significant suppression of plasma GH levels. On the other hand, in all catheterization a marked increase in plasma corticosterone (CS) levels was observed. When the tibia was broken in anesthetized rats, plasma GH levels dropped within 15 min, then gradually increased. However, use of a rubber band tourniquet for a long period caused a marked suppression of GH within 15 min which was maintained for 75 min. If the rubber band was removed 15 min after application, plasma GH levels gradually increased to pre-stress levels in 60 min. A spinal cord section prevented the suppressive effects of the rubber band tourniquet and tibia break on GH release. These results indicate that a strong stress, such as a rubber band tourniquet, inhibits the stimulatory effect of PB on GH release as long as the stress is continued.

ISSN:0028-3835    

DOI:10.1159/000122764

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Lactating female rats were infused with the serotonergic neurotoxin, p-chloramphetamine (PCA), via stainless steel cannulae implanted into either the 3rd or the lateral ventricle. Those mothers receiving the drug in the 3rd ventricle sustained a more severe depletion of hypothalmic serotonin (43% vs 23%) and a significantly greater incidence of pup mortality (98% vs 48%) than those receiving the drug in the lateral ventricle. Coincident with the depletion of hypothalmic serotonin was a reduction in serum prolactin (Prl). Subcutaneous (s.c.) injections of Prl into each group of females sharply reduced the number of pup deaths. It was concluded that hypothalmic serotonergic neurons mediate the suckling-induced release of Prl necessary for the maintenance of lactation.

ISSN:0028-3835    

DOI:10.1159/000122765

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Aminergic regulation of growth hormone (GH) and prolactin (Prl) was studied in male adolescent baboons by i.v. infusion of dopamine (DA), norepinephrine (NE), thyrotropin-releasing hormone (TRH), phentolamine, haloperidol, and inhibitors of DA-β-hydroxylase and peripheral decarboxylase. 20-min infusion of DA (40 µg/kg·min) and 60-min infusion of NE (0.4 µg/kg·min) stimulated GH release. The DA-induced GH release was suppressed by concomitant infusion of FLA 63 (inhibitor of NE synthesis from DA) and by phentolamine, indicating α-adrenergic mediation of GH release. Micro-injection of DA (0.8 µg/kg) into the medial basal hypothalamus (MBH) lowered basal GH. Prl was released by i.v. TRH, and this effect was suppressed by i.v. DA but not by i.v. NE. Blockade of peripheral decarboxylase by carbidopa elicited a marked and sustained rise in Prl which was inhibited by i.v. DA. Microinjection of NE (0.8 µg/kg) into the MBH released Prl. These data indicate that in the MBH, α-adrenergic mechanisms release GH and Prl, and that dopaminergic mechanisms sup

ISSN:0028-3835    

DOI:10.1159/000122766

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

The effects of altering the concentrations of various cerebrospinal fluid (CSF) cations on hypothalamo-hypophyseal-adrenocortical (HHA) activity were investigated in conscious cats. The cerebroventricles were perfused with CSF containing high or low [Na+], [K+], [Li+], [Ca2+] and [Mg2+] for 60 min and plasma samples taken periodically for analysis of cortisol. The results demonstrate that changing CSF [Na+] or [Li+] does not substantially alter plasma cortisol levels. Although individually elevating CSF [K+], [Ca2+] or [Mg2+] does not affect plasma cortisol levels, reducing these CSF cations activates the HHA system and the latter in turn is inhibited by the addition of dexamethasone (DEX) to low cation CSF. The excitatory action of reduced [Ca2+] is also inhibited by the addition of norepinephrine to the perfusion fluid, suggesting that lowering this cation affects the HHA system by preventing the release of the adrenergic neurotransmitter. Furthermore, these data suggest that in conscious unrestrained cats basal HHA activity is dependent to some extent upon normal brain extracellular [K+], [Ca2+] and [Mg2+].

ISSN:0028-3835    

DOI:10.1159/000122767

出版商:S. Karger AG    

年代:1978

数据来源: Karger

摘要:

Normal and castrated male rats were injected subcutaneously (s.c.) with a homologous preparation of prolactin (Prl) for 4½ days, and serum levels of LH and FSH were measured at the end of the treatment. LH was undetectable in normal animals, injected either with Prl or with the vehicle. The treatment produced a significant reduction of the levels of LH in the castrated animals. No effect on FSH levels could be observed in either the normal or the castrated animals. The only relevant autopsy finding was a reduction of pituitary weight in normal animals treated with Prl. No effect on the weight of the testes or of the sex accessories was observed. It is suggested that Prl may directly interfere with the central mechanisms which control LH secretion

ISSN:0028-3835    

DOI:10.1159/000122768

出版商:S. Karger AG    

年代:1978

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000122769

出版商:S. Karger AG    

年代:1978

数据来源: Karger