EFFECTS OF ANGIOTENSIN-II AND ANGIOTENSIN-IV ON GENICULATE ACTIVITY IN NONTRANSGENIC AND TRANSGENIC RATS

Microiontophoretic ejection of angiotensin II and angiotensin IV in th e vicinity of geniculate neurons was used to study the effects of thes e peptides on the discharge rate and the discharge pattern of extracel lularly recorded activity. The main aim of the experiments was to stud y the effects of angiotensins in different strains of rats anesthetize d with urethane (normotensive Wistar, normotensive Sprague-Dawley and hypertensive, transgenic (TGR(mREN2)27) rats). Both angiotensins mostl y increased the spontaneous activity of angiotensin-sensitive genicula te neurons in all strains. Angiotensin II reduced the number of bursts in most neurons, whereas angiotensin IV significantly enhanced it. In hibitory effects of angiotensins on spontaneous as well as on light-ev oked activity could be effectively blocked by GABA(A) or GABA(B) recep tor antagonists. Therefore, it can be supposed that angiotensin-contai ning afferent fibers innervate both projection and local circuit neuro ns of the dorsal lateral geniculate nucleus. In addition, angiotensin II suppressed excitation induced by glutamate receptor agonists in mos t neurons tested. Angiotensin-induced effects could be blocked by spec ific receptor antagonists. There were no significant differences in th e effects of angiotensins in the various strains of rats, except for t he latencies of the neuronal responses to the iontophoretic ejection o f angiotensins. (C) 1997 Elsevier Science B.V.