Histofluorescence studies of the effect of AOAA and etomidate on catecholamine terminals. Possible GABA-NA interaction in the cerebellar cortex.

The effect of two GABA-ergic drugs: aminooxyacetic acid (AOAA) (37,5 mg/kg) and etomidate (2 X 10 mg/kg) on noradrenergic (NA) and dopaminergic (DA) neurons in the rat brain was studied using the Falck-Hillarp histofluorescence method for monoamines. Both drugs enhanced the catecholaminergic fluorescence in NA terminals in the cerebellar cortex, which suggests an increase in NA content there. This effect was blocked by pretreatment with picrotoxin, a Gaba receptor blocking compound. The increase in fluorescence was also observed in DA terminals in nucleus caudatus-putamen after AOAA (but not after etomidate) and this effect was blocked by picrotoxin in 3 out of 5 rats. The obtained results indicate that apart from previously described GABA-DA interaction in the striatum, there exists also GABA-NA interaction seen in the cerebellar cortex.