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

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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.