The use of intracellular dialysis to study signal transduction coupling in the squid giant axon

The squid giant axon has proved a useful model in the study of ionic channel gating, intracellular homeostasis and receptor-mediated signal transduction leading to generation of intracellular second messengers. In the latter category, previous studies on activation of adenylate or guanylate cyclase have used intact and intracellularly perfused axons to investigate the effects of extra- and intracellular agents on the transduction processes. However, the perfusion of the axon interior washes out many factors which may be important in the processes under study. We introduce here the use of porous cellulose dialysis tubing as a means to circumvent these problems. We find that this dialysis technique is a simple procedure to set-up, and the serotonin/G-protein/adenylate cyclase system can readily be studied in the dialysed axon. This approach should allow investigation under conditions which retain asymmetric transmembrane conditions.