Do D2-like dopamine receptors mediate neuronal excitation or inhibition: some functional-behavioural implications.

Few controversies in contemporary neuroscience have endured as long as that concerning the immediate neurophysiological effect(s) of 'D2-like' dopamine receptor activation. While the issue is of fundamental importance, it could be argued that the matter is more abstract and of less consequence than clarifying receptor-mediated actions at other, more functional levels from second messenger through neurochemistry to behaviour. Yet it is not possible to define fully these processes without insight into the immediate neurophysiological action. This necessity has been accentuated by a number of recent developments, including (i) recognition of multiple, complex forms of functional interactions between 'D2-like' and 'D1-like' receptor families which ultimately regulate so many forms of behaviour and (ii) the ongoing debate as to the extent to which members of 'D1-like' and 'D2-like' receptor families might be co-localised on the same neuronal membrane to subserve such interactions. Full specification of these phenomena requires a clear understanding of the relevant neurophysiological events.