Summary: Tsai et al. (2009)

Dopaminergic (DA) neurons are intrinsically involved in motivated behaviours and dopamine signalling can be altered by natural rewards and drugs of abuse. Changes in the firing patterns of these neurons could elicit reward-related behaviours, however, it in unclear whether this alone is sufficient to induce a response. Tsai et al. (2009) used a Cre-inducible adeno-associated virus vector carrying a gene encoding the light-activated cation channel, channelrhodopsin-2 (ChR2) to selectively control DA neurons in freely behaving mammals. They found that ChR2-EYFP co-localises with endogenous TH in coronal VTA sections. They also used whole-cell patch clamps to assess the potential for optogenetic control of transduced cells. ChR2-EYFP-expressing cells showed electrophysiological properties typical of DA neurons, indicating that ChR2 expression alone can not alter basic physiology. They also tested for behavioural conditioning effects of phasic DA neuron activity in mice and found that mice developed a clear place preference associated with phasic optical stimulation. These results show that DA neuron activity can be selectively regulated and demonstrate that phasic dopaminergic activity can mediate behavioural conditioning in mammals.