Possible Functional Differentiation between the Stores from which Adrenergic Nerve Stimulation, Tyramine and Amphetamine Release Noradrenaline

Abstract

Abstract Effects of inhibition of monoamine oxidase and tyrosine hydroxylase on the contraction of rat lower eyelid and pressor response to tyramine, amphetamine and adrenergic nerve stimulation have been studied. Inhibition of MAO markedly enhanced both the peak and the duration of response of the eyelid to tyramine and amphetamine while only moderately augmenting the durations of pressor response to tyramine. Contraction of the eyelid to nerve stimulation was not affected. Inhibition of tyrosine hydroxylase abolished the contraction of the eyelid to amphetamine while only slightly reducing that to tyramine. The contraction of the eyelid to nerve stimulation was not affected. The results suggest that nerve stimulation, tyramine and amphetamine release noradrenaline from different stores. The nature of these stores is discussed.