ABSTRACT
Dopamine is the prototype of a modulatory neurotransmitter. Although it seems to be universally utilized in metazoans, most of our knowledge about dopamine physiology has been obtained from studies conducted in mammals. In these species, dopamine contributes to many functions of the nervous system, including modulation of sensory perception in the retina and olfactory bulb, regulation of hormone release in the pituitary gland, control of body temperature and food intake, or tuning of sensorimotor cues. Dopamine systems are required to maintain or to manifest reward values of life experiences and, thus, motivation or aversion. In vertebrates, the various effects of dopamine on physiological systems or organs are mediated solely by multiple metabotropic membrane receptors coupled to heterotrimeric G proteins.1
