5-HT1A receptors activate a potassium conductance in rat ventromedial hypothalamic neurones.

The extracellularly recorded firing rate of rat ventromedial hypothalamic neurones in vitro was inhibited by 5-hydroxytryptamine (5-HT), 5-carboxamidotryptamine (5-CT), 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) and buspirone, 2-methyl-5-HT was relatively ineffective. At 1 microM, spiperone and cyanopindolol antagonised the 5-CT induced inhibition, MDL 72222 (10 microM) and ketanserin (1 microM) did not. Intracellular recordings with voltage-clamp revealed that 5-HT and 5-CT evoked a tetrodotoxin-resistant outward current with a reversal potential of ca. -100 mV. 5-HT1A receptors likely activate a potassium conductance on these neurones.