电损毁海马CA_3区及连合前穹窿对大鼠血浆胰岛素水平及胰岛细胞的影响

电损毁大鼠海马CA_3区(HCA_3-EL)或连合前穹窿纤维(ACHF-EL)后,其血浆胰岛素基础水平明显升高。HCA_3-EL两周后,大鼠空腹血糖浓度增高,且糖耐量降低。但胰岛B细胞对葡萄糖刺激之分泌反应却显著增强。HCA_3-EL或ACHF-EL大鼠经静脉糖耐量试验(IVGTT)后,其胰岛A细胞内胰高血糖素样及B细胞内胰岛素样免疫阳性物质的相对含量均明显低于对照组。HCA_3-EL组大鼠胰岛中生长抑素样免疫阳性物质的相对含量及阳性细胞数目均较对照组减少,而胰岛中胰多肽样免疫阳性物质却无明显变化。上述结果表明,海马CA_3区(HCA_3)及连台前穹窿(ACHF)对胰岛素的分泌有紧张性抑制作用。

EFFECTS OF ELECTRICAL LESIONING OF HIPPOCAMPAL CA_3 REGION AND ANTERIOR COMMISURA HIPPOCAMPI FORNIX ON PLASMA INSULIN LEVEL AND ISLET CELLS IN THE RAT

Bilateral electrical lesioning of the hippocampal CA_3 region (HCA_3-EL)or anterior commisura hippocampi (ACHF-EL) caused marked elevations in plas-ma basal levels of insulin. 2 weeks later, fasting blood glucose levels were also aug-mented with decreased glucose tolerance. In contrast, the secretory responseof pancreatic B cells to glucose stimulation was markedly enhanced. Following intra-venous glucose tolerance test (IVGTT), the relative amounts of glucagon-like andinsulin-like immunoreactants were reduced in the pancreatic islets of both HCA_3-EL and ACHF-EL rats in comparison with the controls. In the HCA_3-EL group,the relative amounts of somatostatin -like immunoreactants and gross numbers ofsuch immunostained cells in islets were also decreased as compared with the control.No difference was seen in pancreatic-polypeptide - like immunoreactivities as as-sessed by immunohistochemistry plus microphotometry method. The above resultssuggest strongly that HCA_3 and ACHF exert a tonic inhibitory action on theinsulin secretion in the rat.