Gamma-aminobutyric acid-induced responses in acutely dissociated neurons from the rat sacral dorsal commissural nucleus.

摘要

The electrophysiological and pharmacological properties of GABA-activated Cl- currents (IGABA) were investigated in enzymatically dissociated rat sacral dorsal commissural nucleus (SDCN) neurons using the nystatin perforated patch recording configuration under voltage-clamp conditions. Exogenous application of GABA to SDCN neurons induced Cl- currents which increased in a concentration-dependent manner. Bicuculline (BIC) and strychnine (STR) antagonized the IGABA in a concentration-dependent manner. Zn2+ suppressed the IGABA with an IC50 of 2.8 X 10(-5) M. Muscimol mimicked the IGABA, while baclofen evoked no response. Pentobarbital (PB) and 5beta-pregnan-3alpha-ol-20-one (pregnanolone, PGN) also induced GABAA-mimic Cl- currents. Diazepam (DZP), PB and PGN all enhanced the IGABA by increasing the apparent affinity of the GABAA receptors to GABA. Moreover, spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) were observed in mechanically dissociated SDCN neurons attached with synaptic boutons, so called 'synaptic bouton preparation'. These results indicate that SDCN neurons express GABAA receptors with relatively low sensitivity to Zn2+ inhibition, and that GABA may have a functional role as an inhibitory transmitter in the SDCN regulating nociceptive, analgesic, and autonomic functions.