Evidence that activation of central 5-HT(2B) receptors causes renal sympathoexcitation in anaesthetized rats

Abstract

1. The effects of injections i.c.v. of α-methyl-5-(2-thienylmethoxy)-1H-indole-3-ethanamine (BW723C86; 0.02-2 μmol kg-1), a 5-HT(2B) receptor agonist, on renal sympathetic and phrenic nerve activity, mean arterial blood pressure and heart rate were investigated in α-chloralose anaesthetized rats pretreated with a peripherally acting 5-HT2 receptor antagonist. 2. BW723C86 i.c.v. caused a dose-related increase in renal nerve activity reaching a maximum of 67 ± 6, which at the highest dose was associated with a small and maintained fall in mean arterial blood pressure of 7 ± 3 mmHg. These changes were not associated with any significant changes in heart rate or phrenic nerve activity. 3. BW723C86-evoked increases in renal nerve activity and hypotension were attenuated by pretreatment (i.c.v.) with SB204741 (300 nmol kg-1; a 5-HT(2B) receptor antagonist) but not by the same dose (i.c.v.) of ketanserin (a 5-HT(2A) receptor antagonist) or RS102221 (a 5-HT(2C) receptor antagonist). None of these antagonists alone had any effect on the variables being measured. 4. It is concluded that central 5-HT(2B) receptors may play a selective role in the control of sympathetic supply to the kidney, which could be important in the central mechanisms involved in blood volume regulation.