Kidney function after JCV infusion of histamine and H1- or H2-agonists in hydrated conscious goats [proceedings]

Plasma vasopressin levels after I.C.V. infusion of histamine agonists in the conscious goat

Histamine H1-agonists 2-pyridylethylamine (2-PEA) and 2-methylhistamine and H2-agonists 4-methylhistamine, dimaprit and impromidine were given i.c.v. to conscious goats and the release of arginine vasopressin (AVP) was measured. 2-PEA at very low doses (9 and 27 mumoles/animal, equivalent to H1-activity of about 0.5 and 1.5 mumoles histamine, resp.) significantly increased plasma AVP. The H2-agonists did not cause consistent changes in AVP even if their relative doses were higher. It is concluded that the vasopressin releasing effect of histamine is due to H1-receptor activation.

Antidiuresis induced by infusions of histamine into the brain ventricles of conscious hydrated goats

Histamine was infused into the third or lateral ventricle of conscious hydrated goats, and urine samples were analyzed for volume, osmolality and electrolytes. Doses of 10--1000 microgram of histamine induced dose-dependent antidiuretic responses both as to the maximum osmolality and the duration of the osmolality increase. Urine osmolality began to rise within a few minutes, reached its maximum within 0.5--2 h and was elevated for 1.5--4 h, depending on the dose. Thereafter a second increase in osmolality often occurred, which lengthened the effect of histamine dose-dependently up to about 10 h with the largest dose of histamine. Histamine (50--300 microgram) and the control solution given into the lateral ventricle increased the excretion of Na+ into the urine. After the largest dose of histamine (1000 microgram), however, the excretion of Na+ was significantly lower than in the control experiments. After the larger doses of histamine, effects on motor or autonomic functions were seen. These included decreased spontaneous motor activity, increased respiratory rate, defecation and miosis. It is suggested that the site of action of histamine is central, and that the release of vasopressin through the activation of the neurosecretory system is probably involved. In addition the changes in electrolytes may suggest an involvement of the release of other factors such as prolactin.