Physiological regulation of neurohypophyseal kappa-opiate receptors

Quantitative autoradiography was used to examine the characteristics of kappa-opiate receptor binding in neural lobe sections from dehydrated rats and water-sated homozygous Brattleboro rats. The density of kappa-sites was decreased by 40% and 44%, respectively, after 5 days of water deprivation or hypertonic saline. Both the density and affinity of kappa-receptor sites were lower in homozygous Brattleboro rats. We suggest that kappa-receptor down-regulation occurs as a result of elevated release of opioid peptides induced by chronic osmotic stimulation.