Tyramine‐induced noradrenaline release from rat brain slices: prevention by (‐)‐deprenyl

Abstract

Clorgyline (1 and 10 μM) and (+)‐deprenyl (10 μM) both significantly potentiated the tyramine (100 μM)‐induced release of [3H]‐noradrenaline from rat cerebral cortex slices. (‐)‐Deprenyl (50 μM) significantly reduced it, while lower concentrations had no effect on noradrenaline release. However, in combination, 1 μM (‐)‐deprenyl blocked the release‐facilitating action of 1 μM clorgyline, and 10 μM (‐)‐deprenyl that of 10 μM (+)‐deprenyl. Low concentrations of (+)‐ and (‐)‐deprenyl (1 and 10 μM), both selectively inhibited phenylethylamine oxidation by monoamine oxidase B. Higher concentrations of (‐)‐deprenyl (20 and 50 μM) also inhibited 5‐hydroxytryptamine oxidation by monoamine oxidase A. Clorgyline (1 and 10 μM) inhibited both enzymes. Thus, the effects of these drugs on noradrenaline‐release cannot be explained solely in terms of irreversible inhibition of monoamine oxidase A and B, and other possible mechanisms are discussed. If the brain‐slice model faithfully mirrors the sequence of events manifesting peripherally as the tyramine hypertensive response (‘cheese effect”), then it is possible that low doses of (‐)‐deprenyl, administered with antidepressant monoamine oxidase inhibitors, can prevent this adverse reaction.

Sympathetic nerve-derived ATP regulates renal medullary vasa recta diameter via pericyte cells: a role for regulating medullary blood flow?

“…Kidney slices were superfused with PSS alone for 70 s to establish a baseline vessel diameter at the pericyte and non-pericyte site. Slices were then exposed to tyramine [1 μ M; for ~150 s, sufficient time to evoke neurotransmitter release (Glover et al, 1983)], ATP (100 μ M), suramin (100 μ M), or combinations of the agents, before being subjected to a PSS wash. Compounds were purchased from Sigma-Aldrich Ltd, Dorset, UK, and working solutions were prepared in oxygenated PSS.…”

Modification of blood pressure and nictitating membrane response to sympathetic amines by selective monoamine oxidase inhibitors, types A and B, in the cat

“…these effects of selegiline were seen only at very high concentrations. Glover et al (1983) have demonstrated that relatively low concentrations of selegiline (1 !LM) can antagonize tyramine-induced noradrenaline release from rat cerebral cortex slices.…”