Nicotine increases the firing rate of dopamine-producing ventral tegmentum neurons by acting on nicotinic receptors expressed on their surface; opioids, cannabinoids, and benzodiazepines increase their firing rate indirectly, by inhibiting the activity of GABA-producing interneurons in the ventral tegmentum; and psychostimulants such as cocaine, amphetamines, and ecstasy block the dopamine transporter, a membrane protein that normally reabsorbs dopamine once it has been released by neurons into the synaptic cleft.
