Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598439
Title: Investigations into the function and regulation of cholecystokinin receptors in the rat hypothalamus
Author: Day, Nicola Caroline
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 1989
Availability of Full Text:
Full text unavailable from EThOS. Please contact the current institution’s library for further details.
Abstract:
1. The present study examined the function and regulation of cholecystokinin receptors in the rat hypothalamus, using the technique of in vitro receptor autoradiography, in conjunction with radioimmunoassay, in vitro electrophysiology and stereotaxic surgery. 2. Cholecystokinin receptors were localized in the supraoptic, paraventricular, ventromedial and dorsomedial nuclei of the hypothalamus. Competition studies revealed that cholecystokinin receptors in the supraoptic nucleus exhibited the specificity of central rather than peripheral cholecystokinin receptors. 3. Cholecystokinin receptor density was greatly elevated in the supraoptic and paraventricular nucleus of salt-loaded (2% sodium chloride), water-deprived and homozygous Brattleboro rats compared to control animals; this increase occurred preferentially in those areas containing predominantly oxytocin neurones. The increase in cholecystokinin receptor density in the supraoptic nucleus of salt-loaded rats was reversed upon rehydration. There was no change in cholecystokinin receptor binding in the supraoptic nucleus of lactating rats compared to control animals. Eledoisin receptor binding was decreased in the supraoptic and paraventricular nuclei following salt-loading. 4. The effect of cholecystokinin on the extracellular activity of neurones in the paraventricular nucleus in hypothalamic slices from control and salt-loaded animals was investigated. There was a large proportion of fast firing (possibly osmotically stimulated) cells which increased their firing rate in response to cholecystokinin in 'salt-loaded' slices, whereas no fast firing cells did in control slices. The large proportion of CCK-responsive fast firing cells in 'salt-loaded' slices may represent an electrophysiological correlate of increased CCK receptor density in the supraoptic and paraventricular nucleus of salt-loaded animals. 5. Central (i.c.v.) administration of caerulein to rats caused an increase in the plasma levels of oxytocin. This may have resulted from an interaction of caerulein with cholecystokinin receptors in the supraoptic and paraventricular nuclei. 6. Electrolytic lesions of the anteroventral third ventricle region did not attenuate the increase in cholecystokinin receptor density in the supraoptic nucleus elicited by salt-loading, although vasopressin and oxytocin release were attenuated. This implies that afferents from the anteroventral third ventricle region were not required for the osmotic upregulation of cholecystokinin receptor density in the supraoptic nucleus, and suggests that elements in this nucleus remain osmoresponsive in the absence of excitatory input from the anteroventral third ventricle region.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.598439  DOI: Not available
Share: