GABAA-receptor-activated current in dorsal root ganglion neurons freshly isolated from adult rats.

1. gamma-Aminobutyric acid (GABA) is the major inhibitory neurotransmitter affecting dorsal root ganglion (DRG) neurons. This study compares properties of current activated by the GABAA receptor in two populations of DRG neurons. DRG neurons were isolated from adult rat with the use of enzymatic and mechanical means. Within hours of being isolated, neurons were recorded from with the use of the whole-cell variant of the patch-clamp technique. 2. One population of neurons exhibited an afterdepolarizing potential (ADP), a low threshold for action-potential generation (-45 to -50 mV), a short-duration action potential (less than 2 ms) that was abolished in the presence of 1-2 microM tetrodotoxin (TTX), and an insensitivity to 50 nM capsaicin. The second population of neurons exhibited a high threshold for action-potential generation (less than -40 mV), a shoulder on the falling phase of the action potential, insensitivity of action-potential generation to TTX (1-2 microM), and a depolarizing response to application of 50 nM capsaicin. 3. Sensitivity to GABA (over the range of 1-1,000 microM) was comparable for the two populations of neurons. 4. GABA-activated current was greater in ADP neurons than in non-ADP-type neurons of a comparable diameter (30-50 microns). The mean +/- SE amplitude of current activated by 10 microM GABA in ADP neurons was 0.310 +/- 0.050 nA (range = 0.110-0.460 nA, n = 8), and 0.037 +/- 0.016 nA (range = 0.010-0.130 pA, n = 7) in non-ADP neurons. Ten microM GABA elicited cell firing in ADP neurons but not in non-ADP neurons.(ABSTRACT TRUNCATED AT 250 WORDS)