摘要:

After finding that dopamine can cause extensive changes in mammotroph ultrastructure within 2 min of administration, we further examined mammotrophs 20 and 40 min after dopamine injection when prolactin secretion had resumed. Dopamine (1,000 µg/kg) was injected into the right atrium of estradiol-primed male rats through indwelling cannulae. Rats were killed by decapitation 2, 20 and 40 min after dopamine treatment and their pituitaries were processed for electron microscopy. Within 2 min of administration, dopamine completely stopped prolactin release and significant changes in mammotroph ultrastructure were observed: (1) peripheral relocation of rough endoplasmic reticulum (RER) (‘dopamine barrier’); (2) fewer secretory granules in close proximity to the cell membrane; (3) fewer exocytoses, and (4) increased numbers of intracellular bodies’ associated with secretory granules (putative granule disposal system). 20 min following dopamine administration, when prolactin secretion had resumed, there appeared to be a breaking up of the ‘RER barrier’ in that more vesicular elements were seen and the amount of peripheral RER was reduced; more granules were adjacent to the cell membrane and exocytotic figures were more numerous. ‘Intracellular bodies’ decreased in number. By 40 min, mammotrophs appeared to resemble those of estradiol-primed controls with the RER stacked to one side of the cell and small numbers of ’intracellular bodies’. The correlation between ultrastructural changes in mammotrophs and prolactin release implies that the ‘RER barrier’ is part of a mechanism by which prolacti

ISSN:0028-3835    

DOI:10.1159/000124110

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Choline acetyltransferase (CAT) activity of the striatum, preoptic area (POA), and pars distalis (PD) of the anterior pituitary gland was measured on each day of the 4-day estrous cycle of adult Wistar rats. Only in the PD did CAT activity vary significantly during the cycle, with the activity being lower during estrus than at other stages of the cycle. The CAT activity of the PD was extremely low, approximately 500 nmol/h/g protein, and, therefore, the specificity of the CAT activity of the PD was verified in studies on substrate requirement, the effect of a CAT inhibitor, and by paper chromatography of the reaction products. Measurement of CAT activity in saline-perfused glands, in sections of tissue taken from the lateral extremes of the PD and in hypophysial portal blood showed that the CAT activity of the PD was intrinsic, and not due to CAT activity in entrapped blood or adjacent tissues. The precise cellular origins of CAT in PD and the significance of the cyclical variation require further investigation.

ISSN:0028-3835    

DOI:10.1159/000124111

出版商:S. Karger AG    

年代:1985

数据来源: Karger

摘要:

Multiunit activity (MUA) of the suprachiasmatic nucleus (SCN) of the hypothalamus and medial preoptic area (MPOA) was recorded in chronically implanted, freely moving female rats. The integrated MUA of the SCN and MPOA was significantly higher in the dark than in the light period of day. Superimposed upon this diurnal rhythmicity in the SCN were 3.0- to 3.5-hour ultradian oscillations of MUA, with the fluctuations showing the highest variability at night. A significant increase in SCN MUA consistently preceded the offset of light by 1 h, whereas during the dark-light transition a marked decrease of neuronal firing occurred after the onset of light. Analysis of MUA base level – recorded during slow wave sleep – revealed that the average activity in the SCN was lowest on the day of diestrus-II, began to increase on proestrus night, and reached the highest values during estrus. Bilateral transection of the optic nerve, 4–6 weeks prior to electrical recordings, abolished the estrous cycle and the circadian pattern of neuronal firing of the SCN. An ultradian oscillation of integrated MUA in blind rats occurred with the same average intervals (3.0–3.28 h) but the amplitude was much higher than in intact cycling rats. Data indicate that there are correlated changes in basal MUA levels of the SCN and the stages of the estrous cycle. Furthermore, they suggest that maintenance of hormonal cyclicity and circadian rhythm of neuronal function requires intact retinohypothalamic conn

ISSN:0028-3835    

DOI:10.1159/000124112

出版商:S. Karger AG    

年代:1985

数据来源: Karger

ISSN:0028-3835    

DOI:10.1159/000124113

出版商:S. Karger AG    

年代:1985

数据来源: Karger