Effect of alpha-bungarotoxin and etorphine on acetylcholine-evoked release of endogenous and radiolabeled catecholamines from primary culture of adrenal chromaffin cells.

Cell cultures of adrenal medulla have become an important research tool to study basic processes that regulate catecholamine storage, release and synthesis. Release has been studied either by labeling with [3H]norepinephrine and measuring release of radioactivity or by measuring the endogenous catecholamines released with HPLC. Acetylcholine (5 X 10(-6)-10(-4) M) appears to release preferentially norepinephrine, although the cells store more epinephrine than norepinephrine. Etorphine and alpha-bungarotoxin antagonize the release of catecholamines elicited by acetylcholine. This inhibitory action appears to be greater when the measurement of endogenous catecholamines rather than radioactive norepinephrine is used to monitor the action of acetylcholine. The data suggest that the measurement of endogenous catecholamines by HPLC is preferable to the [3H]NE loading and release technique, especially when analyzing the effects of low concentrations of drugs that are thought to affect nicotinic receptor function.