Distribution of gaba-receptors and gaba-carriers in the mammalian nervous system.

1. Extrasynaptic GABA-receptors occur on both neurone somata and unmyelinated axons in the mammalian peripheral nervous system. Activation of these receptors leads to depolarization, reduced spike amplitude and slowed conduction, probably mediated through increased Cl- conductance. 2. GABA also depolarizeds preganglionic nerve terminals in the rat superior cervical ganglion and reduces the release of acetylcholine by preganglionic nerve impulses. 3. The Schwann and satellite neuroglial cells surrounding peripheral unmyelinated axons and neurones possess a GABA-carrier promoting net uptake of GABA at external concentrations greater than or equal to 1 microM. 4. The possible significance of extrasynaptic receptors and carriers for GABA is discussed.