1. Conductance changes in the acini of the cockroach salivary gland have been examined during nerve stimulation by means of two intracellular electrodes placed in the same acinus, the first electrode being used for recording membrane potential and the second for current injection. 2. The transient hyperpolarization (secretory potential) in the acinus evoked by nerve stimuli is accompanied by a rise in membrane conductance. The conductance, however, remains high for a longer period than that of the response. 3. Applying the analysis of Trautwein & Dudel (1958) to the secretory potentials recorded in the acinus (assumed to behave electrically like a single cell) gives estimates of the ‘transmitter equilibrium potential’. The values indicate that the neurotransmitter increases the membrane potassium conductance. 4. The hyperpolarization of the acinus evoked by 10−6 M dopamine in the bathing fluid is also associated with an increase in membrane potassium conductance.
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