Stimulation electrically and by acetylcholine of the rat hypothalamus in vitro

摘要: 1. The hypophysiotrophic area of the rat hypothalamus was studied in vitro. preparation remained viable for at least 3 hr and showed oxygen consumption varying between 68·9–120 μmole/g.hr. tissue potassium ion content (per unit wet weight) fell to about 50% vivo concentration during this time compared with 15% presence ouabain (10−4 M). Histological examination incubated variable perineuronal oedema but nuclei were normal appearance none pyknotic changes that would be associated cell degeneration. 2. Corticotrophin releasing hormone (CRH) medium pooled from five twenty hypothalami assayed twelve rats which median-eminence lesioned 48 earlier. In vitro corticosterone production quartered adrenals used as end point assay. Regression lines dose—response curves ACTH, crude CRH different volumes electrically stimulated parallel. output maximal 75 Hz 100 μA when square-wave pulses lasted 1 msec. No activity found on stimulation cerebral cortex or thalamic pieces equivalent size. 3. Hypothalami taken rats, adrenalectomized 7–14 days previously, released several-fold more into electrical than initial tissue, showing capable synthesizing intact considerably less 12 14 day rats. hyper-secretion observed abolished by pre-treatment 5 mg/100 g s.c. 24 before removal tissue. It is therefore proposed delayed negative feed-back action hypothalamic level suppression synthesis effect secretion secondary synthesis. 4. Ca2+ essential release CRH. 5. increases linearly doses acetylcholine 5·5 × 10−15-5·5 10−14 M. Cerebral no activity. reduced atropine (3·5 10−13 Median eminence-pituitary stalk fragments (which contain mainly terminal axons neurones) activate using hypothalamus. Acetylcholine may act a neurotransmitter dendritic neurone.