The regulation of norepinephrine synthesis in sympathetic nerves: effect of nerve stimulation, cocaine, and catecholamine-releasing agents.

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Abstract
Electrical stimulation of the hypogastric nerve of the isolated guinea pig vas deferens preparation is associated with an accelerated rate of formation of H3-norepinephrine from [3,5-H3]-tyrosine. Tyramine and pheniprazine, which are known to release bound norepinephrine and to inhibit monoamine oxidase, inhibit norepinephrine synthesis and partially nullify the increased synthesis of norepinephrine induced by nerve stimulation. Reserpine pretreatment results in a marked inhibition of norepinephrine synthesis in unstimulated preparations; nerve stimulation leads to a considerable increase in norepinephrine synthesis in reserpine pretreated tissues. In the presence of cocaine the rate of norepinephrine synthesis is slightly enhanced. Norepinephrine, 1 [mu]g/ml, inhibits its own synthesis and blocks the accelerated synthesis seen during nerve stimulation. Free intraneuronal norepinephrine appears to be a regulating factor in norepinephrine synthesis.