Novel pathway for an old neurotransmitter: dopamine-induced neuronal calcium signalling via receptor-independent mechanisms.

Dopamine is one of the key neurotransmitters in the central nervous system and plays an important role in physiological processes, as well as in the development of many diseases. Here we report a receptor-independent signalling pathway induced by dopamine in CNS neurons. In cultured neurons from midbrain, cortex and hippocampus, dopamine uptake via dopamine or monoamine transporters induces plasmalemmal membrane depolarization, leading to opening of voltage gated calcium channels and a cytosolic calcium signal. This dopamine-induced calcium signal is unaffected by inhibition of the known dopamine receptors. In anaesthetized rats, application of dopamine in the presence of dopamine receptor antagonists to brainstem structures controlling cardiovascular activity results in an increase in heart rate, arterial blood pressure and sympathetic nerve activity. These data identify a novel dopamine-induced signalling pathway in CNS neurons which may have an important functional role in the central mechanisms controlling complex behaviours.