m-CPP, a 5-HT2C receptor agonist that modifies the perfusion pressure of the hindquarter vascular bed of anesthetized rat

In the present work we studied the actions of the intra-arterial administration of meta-chlorophenylpiperazine (m-CPP - a 5-HT2C receptor agonist) in the hindquarters of the anesthetized rat. The lowest doses used (0.001, 0.01, 0.1, 0.25 and 0.5 mug/kg) induced vasodilatation whereas the highest doses produced vasoconstriction ( 1, 6.25, 12.5 and 25 mug/kg). Both vasodilatation and vasoconstriction were inhibited by the 5-HT1,2 receptor antagonist methiothepin, whereas the 5-HT2 receptor antagonist ritanserin blocked only the vasoconstrictor responses. 1-[4-(1-Adamantanecarboxamido) butyl]-4-(2-methoxyphenyl) piperazine (a 5-HT1A receptor antagonist) and ICI 118,551 (a beta(2)-receptor antagonist) failed to modify the vasodilator responses of m-CPP. Both BRL 15572 ( a 5-HT1D receptor antagonist) and GR 55562 ( a 5-HT1B receptor antagonist) only partially inhibited this action. Our data reveal that m-CPP induces the 5-HT1 and/or non-specific vasodilator effect and 5-HT2 vasoconstrictor effects in the hindquarter vascular bed of the rat. Copyright (C) 2005 S. Karger AG, Basel.