RENAL VASOCONSTRICTOR RESPONSE TO 5-HYDROXYTRYPTAMINE IN THE IN-SITU AUTOPERFUSED RAT-KIDNEY - INVOLVEMENT OF ANGIOTENSIN-II AND THE 5-HT2 RECEPTOR ACTIVATION

Using a number of agonist and antagonist compounds, we attempted to ch aracterize the responses and receptors involved in the effects of 5-hy droxytryptamine (5-HT) in the in situ autoperfused rat kidney. An intr a-arterial (i.a.) bolus injection of 5-HT (0.0125 to 0.1 mu g/kg) incr eased renal perfusion pressure in a dose-dependent way but did not cha nge the systemic blood pressure. The 5-HT2 receptor agonist, (1-(3-chl orophenyl) piperazine), m-CPP, caused a local vasoconstrictor effect i n the autoperfused rat kidney. An intra-arterial injection of 5-carbox amidotryptamine, 5-CT and 1-(m-chlorophenyl)-biguanide (m-CPBG) did no t modify the renal perfusion pressure. The vasoconstrictor effect elic ited by 5-HT and m-CPP was significantly decreased by ritanserin, enal april and losartan but was not modified by prazosin, propranolol or in domethacin pretreatment. Our data suggest that the vasoconstrictor ser otonergic response induced in the in situ autoperfused rat kidney is m ediated through angiotensin II activation by a local 5-HT2 receptor me chanism. (C) 1997 Elsevier Science B.V.