Specific enhancement of neuronal responses to catecholamine by p-tyramine.
Extracellular recording and iontophoresis techniques were used to study the interactions of the trace amine, p-tyramine (p-TA) with putative neurotransmitters on single neurones in the cerebral cortex and caudate nucleus of the rat. p-TA, when applied with weak iontophoretic currents which did not result in any change in neuronal firing rate, caused a pronounced potentiation of depressant responses to iontophoretically applied dopamine (DA). Depressant responses of cortical neurones to noradrenaline were also markedly potentiated by weak background application of p-TA. This potentiating action of p-TA was related to the amount of the trace amine applied and was apparently specific for catecholamines, since depressant responses to 5-hydroxytryptamine and gamma-aminobutyric acid were unaffected. Excitatory responses to iontophoretically applied glutamate were also unaltered by weak application of p-TA. Excitatory responses to iontophoretically applied glutamate were also unaltered by weak applications of p-TA. Excitatory responses of most neurones to acetylcholine (ACh) were also unaffected by p-TA in the cortex and caudate nucleus. However, responses to ACh of a small number of cells in both brain areas were reduced in size during weak applications of p-TA. It is suggested that p-TA may act as a modulator of neurotransmission, particularly that mediated by DA in the central nervous system.
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D002395:Catecholamines / Q000494:pharmacology*; D002421:Caudate Nucleus / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D004298:Dopamine / Q000494:pharmacology; D004357:Drug Synergism; D004553:Electric Conductivity; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology; D051381:Rats; D012701:Serotonin / Q000494:pharmacology; D014439:Tyramine / Q000494:pharmacology*; D005680:gamma-Aminobutyric Acid / Q000494:pharmacology
D002395:Catecholamines; D012701:Serotonin; D005680:gamma-Aminobutyric Acid; D000109:Acetylcholine; D004298:Dopamine; D009638:Norepinephrine; D014439:Tyramine