Evidence that 5‐hydroxytryptamine release in rat dorsal raphé nucleus is controlled by 5‐HT1A, 5‐HT1B and 5‐HT1D autoreceptors

Abstract

Electrically stimulated 5‐hydroxytryptamine (5‐HT) release was monitored in slices of rat dorsal raphé nucleus (DRN) by fast cylic voltammetry. Pseudo‐single pulse stimulations (5 pulses at 100 Hz) were used to enable the effect of various receptor agonists to be seen without competition from endogenously released transmitter. The selective 5‐HT1A receptor agonist, (+)‐8‐OH‐DPAT (1.0 μm) decreased stimulated 5‐HT release to 31 ± 3% of controls. This decrease was inhibited by the 5‐HT1A receptor antagonists, (+)‐WAY‐100135 (1.0 μm) and WAY‐100635 (0.1 μm) but not by the 5‐HT1D/B antagonist, GR127935 (0.05 μm). The selective 5‐HT1B receptor agonist, CP‐93129 (0.3 μm) decreased stimulated 5‐HT release to 61 ± 4% of control. This effect was antagonized by the 5‐HT1B receptor antagonist, isamoltane (0.5 μm) but not by (+)‐WAY‐100135. The 5‐HT1D agonist, sumatriptan (0.5 μm) decreased stimulated 5‐HT release to 52 ± 2 % of controls. This decrease was blocked by GR‐127935 but not by WAY‐100635. These results suggest that 5‐HT release in the rat DRN is under the control of 5‐HT1A, 5‐HT1B and 5‐HT1D autoreceptors. 1995 British Pharmacological Society