The present study was performed to record the electrical activity of olfactory placode neurons and to check the effect of GABA and bicuculline on it. Olfactory placodes obtained at day 13.5 of gestation were cultured for 1 week on multi-electrode dishes. Olfactory placode neurons showed spontaneous firing, with firing rates of 0.77 +/- 0.05 Hz (0.03-3.82 Hz, n = 12), but there was no bursting activity. Perfusion with 10 microM GABA almost immediately inhibited 8 of 11 firing activities (we could not test it in 1 activity). In contrast, perfusion with 10 microM bicuculline induced facilitation in 5 of 12 activities and did not induce any change in 7 other activities. Statistical analysis by chi(2)-test showed a significant difference in the response of neurons to the two drugs. Fisher's exact probability test showed that the inhibitory effect of GABA was significant (p<0.05) whereas neither the facilitatory effect nor the lack of effect of bicuculline was significant (p>0.1). These results suggest that cultured olfactory placode neurons, even in a probably immature stage, respond to GABA with inhibition, as generally observed at mature stages.