Neuronal responses to ethylenediamine: preferential blockade by bicuculline.

The effects of ethylenediamine have been compared with GABA using two systems: microiontophoretic application to rat neurones in vivo, and superfusion of rat sympathetic ganglia in vitro. Using both techniques ethylenediamine mimicked closely the responses to GABA, showing a potency of 0.044 relative to GABA = 1.0 in the ganglion. Bicuculline, but not strychnine, blocked ethylenediamine and GABA without affecting glycine, and strychnine blocked only glycine, in vivo. It was particularly clear from the in vitro experiments that bicuculline is about twice as effective an antagonist of ethylenediamine than of GABA.