GABA-sensitivity of dorsal column axons: an in vitro comparison between adult and neonatal rat spinal cords

Abstract

In neonatal rat spinal cord, conduction in the dorsal column is reversibly depressed by GABA. We compared the GABA-sensitivity of dorsal columns in neonate versus adult rats, using in vitro isolated dorsal column preparations. The extracellular compound action potential evoked by submaximal stimuli was recorded with a glass micropipette. GABA (10 −4-10 −3 M) reversibly depressed the compound action potential of both neonatal and adult rat dorsal columns. The GABA-induced reduction of dorsal column compound action potential amplitudes was blocked by the GABA A antagonist picrotoxin (10 −3 M) and mimicked by the GABA A agonist isoguvacine (10 −4-10 −3 M). The compound action potential reduction by GABA was far less pronounced on adult dorsal columns. The reduction of compound action potential amplitudes by isoguvacine (10 −4-10 −3 M) was also significantly less in adult dorsal columns. These data suggest that GABA A receptors may play a role in extrasynaptic modulation of spinal long tract conduction in an age-dependent manner.