Selective Activation of Serotonin2C Receptors Stimulates GABA-ergic Function in the Rat Substantia Nigra Pars Reticulata: A Combined in Vivo Electrophysiological and Neurochemical Study.

In vivo electrophysiology and microdialysis were used to investigate the physiological role of 5-HT2C receptors in the control of substantia nigra pars reticulata (SNr) function. Extracellular single-unit recordings were performed from putative GABA-containing neurons in the SNr of anesthetized rats, and local GABA release was studied by in vivo microdialysis in the SNr of awake freely-moving rats. Systemic administration of the selective 5-HT2C receptor agonist (S)-2-(chloro-5-fluoro-indol-1-yl)-1-methylethylamine 1:1 C4H4O4 (RO 60-0175) caused a dose-dependent excitation of about 30% of the SNr neurons recorded. However, the remaining neurons were either inhibited or unaffected by systemi…