The effect of piperidine and pipecolic acid on high potassium-induced release of noradrenaline, serotonin and GABA from rat brain slices.

Abstract

Piperidine has a tranquilizing action, a prolonging action of barbital-induced sleep and a direct hypnogenic effect. Several neurophysiological studies by Juvet suggested that the interaction between noradrenaline (NA) [norepinephrine] and 5-hydroxytryptamine (5-HT) was involved in the sleep-wakefulness mechanism. Therefore, it would be of interest to study whether or not piperidine induces sleep by influence on the function of central monoamine neurons. Pipecolic acid, which has been speculated to be a possible precursor of piperidine in the mouse brain, has a tranquilizing action. The effect of piperidine and D,L-pipecolic acid on a Ca2+-dependent release of L-[3H]noradrenaline (L-[3H]NA), [3H]5-hydroxytryptamine ([3H]5-HT) and [14C]GABA from the rat brain slices preloaded of radioactive amines and acid were investigated. Piperidine 10-4 M did not affect high K+-induced release of L-[3H]NA, [3H]5-HT and [14C]GABA as well as spontaneous release of these amines and acid. D,L-pipecolic acid (10-4 M) significantly increased high K+-induced release of [14C]GABA but not of L-[3H]NA or [3H]5-HT. The hypnogenic and tranquilizing effect of piperidine is apparently due to other mechanism than influence on NA, 5-HT and GABA at nerve terminals of central NA, 5-HT and GABA neurons, and pipecolic acid could potentiate the synaptic transmission of GABA in the CNS.