Embryonic cockroach brain neuronal

Using conventional and whole cell patch techniques, we have current- and voltage-clamped the somata in cultures of dissociated embryonic cockroach brain neurons and preparations of isolated thoracic neurons from locusts to examine their responses to GABA and other putative neurotransmitters and neuropeptides. These neurons respond to the micro-application of GABA with a transient membrane conductance increase. The effect is blocked by picrotoxin but unaffected by bicuculline up to 10M. 

The preparation of the embryonic cockroach brain neuronal cultures is a complicated procedure which has been described in detail by Beadle and Lees ( ). In brief, the brains were dissected from 23-26 day old embryos of Periplaneta americana and broken up by passage through Pasteur pipettes of decreasing diameter. The cultures were initiated in a medium consisting of 5 parts Schneider s Drosophila medium and 4 parts Eagle s Basal medium, and after 7 days growth were transferred to a... 

Figure 1. Responses of current-clamped, cultured, embryonic cockroach brain neurons to putative neurotransmitters and a neuropeptide. The test compounds were applied by pressure ejection from glass micropipettes onto the soma of the impaled neuron. The membrane resistance was monitored by repeated injection of constant-amplitude current pulses.

Figure 2. Currents recorded from a cultured, embryonic cockroach brain neuron intracellularly perfused and voltage-clamped using the whole cell patch method. The intra-electrode [Cl"] was 114 mV and [C1"]Q was 221 mM. For this ratio of [Cl-] across the cell membrane, the Nernst equation predicts a value of -16 mV for the Cl" equilibrium potential...

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