Effect of angiotensin II and eledoisin on cholinergic neurons in rat hippocampus

Angiotensin II and eledoisin modulate drinking behaviour in rats that is mediated by monoaminergic and cholinergic neurons. In the present study we have shown that combined intracerebroventricular injections of either 0.1 or 1.0 microgram doses of angiotensin and eledoisin resulted in a decrease of about 25-35% in activities of choline acetyltransferase, ATP-citrate lyase in the hippocampus. In addition, 1 microgram quantities of these peptides depressed activity of carnitine acetyltransferase but did not alter activity of acetylcholinesterase. On the other hand, the application of 0.1 microgram of angiotensin caused no change in activity of monoamine oxidase A, while 1.0 microgram dose brought about its 67% activation. Eledoisin abolished this effect of angiotensin II. These data provide evidence that angiotensin II and eledoisin evoke non related adaptive changes in cholinergic and monoaminergic neurons of the hippocampus.

Differential effects of angiotensin II and eledoisin on monoamine oxidase A and B activities in rat brain

Intracerebroventricular injections of angiotensin II caused 108, 62, and 54% increases in monoamine oxidase A activities in rat hippocampus, hypothalamus, and striatum, respectively. These activatory effects were abolished by simultaneous injections of eledoisin. No significant changes of monoamine oxidase B activities were found under the same experimental conditions. Neither angiotensin II nor elodoisin changed substrate/inhibitor affinities of both isoenzymes. These data indicate that angiotensin II and tachykinin transmitter systems may exert opposite, long-term regulatory effects on monoaminergic neurons in rat brain.