Influence of neuroglial transport on the action of gamma-aminobutyric acid on mammalian ganglion cells.

1 The effect of inhibiting the transport of gamma-aminobutyric acid (GABA) by neuroglial cells on the depolarizing action of exogenous amino acids on isolated superior cervical ganglia of the rat was studied. 1 Transport (measured by uptake of [3H]-GABA) was inhibited by (a) reducing external [na+] from 143 to 2mM and (b) administering alternative carrier-sbustrates, 3-amino-n-butyric acid (beta-amino-butyric acid, BABA) and (+/-)-nipecotic acid at a concentration of 1 mM. 3 All three procedures enhanced the depolarization produced by low concentrations of GABA (less than or equal to 10 muM) but did not alter the maximum response, nor the response to 3-aminopropanesulphonic acid (a gabamimetic with low affinity for the neuroglial carrier). 4 It is concluded that the neuroglial uptake process can limit the action of exogenous GABA upon neurones, by reducing the interstitial GABA concentration.