On the receptors which mediate the hyperpolarization of salivary gland cells of Nauphoeta cinerea Olivier.

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Abstract
The actions of sympathomimetics and catecholamine antagonists were investigated on the membrane potential and responses to nerve stimulation of acinar cells of the salivary gland of N. cinerea. Hyperpolarizations such as those evoked by nerve stimulation and by low concentrations of adrenaline, noradrenaline and dopamine were not produced by the .alpha.-agonists amidephrine and methoxamine. Isoprenaline was active, but only in concentrations > 100 .mu.M. Tyramine, an indirectly acting sympathomimetic, and high concentrations of methoxamine caused an increase in the rate of the small transient hyperpolarizations sometimes seen in the absence of stimulation. The response to nerve stimulation was unaffected by propranolol (20 .mu.M), an .alpha.-adrenergic antagonist. Phentolamine, an .alpha.-adrenergic antagonist, reduced matching responses to nerve stimulation and to dopamine to about the same extent. As on other systems responsive to low concentrations of dopamine, apomorphine was active, although only in high concentration, and ergometrine and methysergide were antagonistic both to nerve stimulation and to dopamine.