Localization and physiological properties of glycine and GABA receptors in cultures of rat CNS.

Autoradiographic binding studies have shown that 3H-GABA, 3H-glycine, their antagonists 3H-bicuculline and 3H-strychnine were bound to many neurones of cultured rat CNS. In contrast, glial cells did not reveal binding sites for any of the compounds studied. The electrophysiological studies showed that GABA and glycine caused a hyperpolarization of cultured spinal neurones. This hyperpolarization was accompanied by a decrease in membrane resistance which is probably due to an increased membrane permeability to Cl- and K+. On cultured glial cells, both GABA and glycine produced depolarizations which were, however, not associated with a change in membrane conductance. Measurements of the extracellular K+-concentration using ion-sensitive microelectrodes indicated that the glial depolarization was caused by an efflux of K+ from adjacent neurones. From our electrophysiological and autoradiographic studies it is suggested that unlike neurones, glial cells do not possess receptors for GABA and glycine.