Evidence that 5‐HT1D receptors mediate inhibition of sympathetic ganglionic transmission in anaesthetized cats

Abstract

In anaesthetized cats, 5‐carboxamidotryptamine (5‐CT) or 5‐hydroxytryptamine (5‐HT) (0.3–300 μg kg−1, i.v.) inhibited the postganglionic compound action potential evoked by preganglionic electrical stimulation (0.5 Hz) with a similar potency in the stellate and splanchnic ganglia. In the 5‐HT experiments transmission thorough the inferior mesenteric ganglia was also recorded. The maximal inhibitory effect of 5‐HT was greater on the stellate and splanchnic ganglia (60 ± 4 and 52 ± 5%) than on the inferior mesenteric (15 ± 2%). The effects of 5‐HT were unaffected by pretreatment with antagonists (1 mg kg−1;i.v.) for 5‐HT2 (BW501C67), 5‐HT1A (WAY‐100635) and 5‐HT3 receptors (ondansetron). However, responses to both 5‐HT and 5‐CT were attenuated significantly by GR127935 (1 mg kg−1) except the responses to 5‐HT at the inferior mesenteric ganglia. These results are consistent with the involvement of 5‐HT1D receptors mediating inhibition of sympathetic ganglionic transmission in vivo. 1995 British Pharmacological Society