GABA(A) RECEPTOR CURRENTS RECORDED FROM MULLER GLIAL-CELLS OF THE BABOON (PAPIO-CYNOCEPHALUS) RETINA

The effect of gamma-aminobutyric acid (GABA) application on acutely is olated, non-cultivated Muller glial cells from the baboon retina was s tudied using the whole-cell voltage-clamp technique. Application of GA BA (0.1 mM) generated inward currents at a holding potential of -80 mV as well as an increase in current noise. The GABA-activated current h ad a reversal potential of 18.6 mV and was therefore supposed to be a Cl- current (Ed = 5 mV). The GABAA receptor agonist muscimol (0.1 mM) elicited an inward current and bicucullin (0.5 mM), a blocker of the G ABAA receptor, diminished the GABA responses in our experiments comple tely. Baclofen (0.1 mM), a GABAB agonist, neither had an effect when a pplied under conditions where the dominant Muller cell Kf currents wer e unblocked, nor when the K+ currents were blocked by application of B a2+ (1 mM). Glycine (0.1 mM) was ineffective as well. From these resul ts we conclude that the baboon retinal Muller cells possess GABAA rece ptors. However, these have recently been discovered on skate Muller ce lls whereas GABAA receptors could not be found on Muller cells of guin ea pig, pig, mouse, rat and rabbit.