Interaction between cholinergic and opiate receptors of the lateral hypothalamus in the control of renal excretion in rats.

The present study was carried out to investigate the participation and interaction between cholinergic and opiate receptors of the lateral hypothalamus (LH) in the regulation of Na+, K+ and water excretion. Male Holtzman rats were implanted with chronic cerebral cannulas into the LH. Urine was collected over a period of 2 h after injection of carbachol, FK-p33824 + carbachol or naloxone + carbachol into the LH. Carbachol (8 nmol) reduced urinary volume and increased Na+ excretion. Previous injection of FK-33824 (100 ng) into the LH increased the antidiuretic effect of carbachol, but blocked the increase in Na+ excretion and decreased K+ excretion. Naloxone (10 micrograms) produced no changes in the effect of carbachol on renal excretion. These data show an inhibitory effect of opiate receptors on the changes in urinary Na+ and K+ excretion that are induced by cholinergic stimulation of the LH in rats, and a potentiating effect on antidiuresis.