Interaction between desipramine, tyramine, and amphetamine at adrenergic neurones

1. Small doses of tyramine (10 mug/kg intravenously) are taken up by rat heart, which can concentrate the amine 7.3-fold over the plasma level.2. Desipramine (DMI) blocks the uptake of small doses of tyramine by rat heart, but in doses of 20 mg/kg intraperitoneally, it does not affect the cardiac concentrations of tyramine following 20 mg/kg intramuscularly of the drug. The same dose of DMI prevents the depletion of noradrenaline (NA) elicited by intramuscular injection of tyramine 20 mg/kg.3. DMI prevents the depletion of heart NA elicited by (+)-amphetamine 5 mg/kg given intraperitoneally to demedullated rats and enhances the heart concentration of amphetamine.4. Liposoluble amphetamine enters sympathetic nerves by simple diffusion. It is suggested that DMI prevents the release of heart NA caused by this indirect sympathomimetic through an action within the adrenergic neurone.