Dopamine depolarisation of mammalian primary afferent neurones

Dopamine (DA) is an important neurotransmitter or neuromodulator in the mammalian nervous system. As such, it is implicated in the aetiology and therapy of various disease conditions--for example, Parkinson's disease, schizophrenia, Huntington's disease and tardive dyskinesia. However, only limited electrophysiological information is presently available concerning dopamine receptors in the mammalian nervous system, and there are only three reports in which intracellular techniques have successfully recorded the action of DA on individual central neurones. In all cases, DA depolarised the respective neurones. In the periphery, DA is reported to hyperpolarise superior cervical ganglia. However, this hyperpolarisation has been shown to be due to activation of alpha-adrenoreceptors and not to a response of DA on a DA receptor. Peripheral DA actions have also been described presynaptically, but are difficult to study electrophysiologically for technical reasons. As a result, little is known at the membrane level about the effects of drugs thought to modulate or interact with DA receptors. In the present report, we describe a depolarising action for DA on the cat dorsal root ganglion.