Sympathetically evoked secretory potentials in the parotid gland of the cat.

1. In cats under chloralose anaesthesia micro-electrodes were inserted into parotid gland cells. 2. The average resting potential was found to be -35 . 6 +/- 4 . 7 (S.D.) mV. 3. Stimulation of the auriculo-temporal nerve caused hyperpolarizing, or occasionally depolarizing, secretory potentials of 5--10 mV, which were abolishable with atropine. 4. Stimulation of the cervical sympathetic trunk regularly caused, after long latency (several seconds), slow depolarizations of 15--20 mV, accompanied by a decrease in input resistance. They were antagonized by practolol and therefore assumed to be mediated by beta 1-adrenoceptors. Occasionally hyperpolarization, ascribed to an effect on alpha-adrenoceptors, was observed. 5. In many units the slow depolarization on sympathetic stimulation was preceded by short-lasting hyperpolarizing (sometimes depolarizing) transients. They resembled the evoked cholinergic responses but could be abolished not only by atropine but also by guanethidine.