CENTRAL DOPAMINERGIC NEURONS: NEUROPHYSIOLOGICAL IDENTIFICATION AND RESPONSES TO DRUGS**This research was supported by NIMH Grant MH-17871, USPHS Research Scientist Development Award MH-14459 (to G. K. A.), and the State of Connecticut.

Abstract

This chapter describes the neurophysiological identification, and responses to drugs of central dopaminergic neurons. Neurons in the rat brain identified as dopaminergic were found to be remarkably homogeneous with respect to their firing pattern, and responses to drugs and other substances administered systemically, or applied iontophoretically. In these same respects, dopaminergic neurons were clearly distinguishable from neurons in nearby areas, such as the ZR of the substantia nigra, the red nucleus, or the reticular formation. Dopaminergic cells typically show extracellular action potentials with a positive-negative wave form of unusually long duration. They tend to have a regular rhythm and a slow rate of firing in unanesthetised, gallamine-paralyzed preparations, but curiously exhibit an increase in firing rate and a bursting pattern when the animal is anesthetized with chloral hydrate, or halothane. In contrast, ZR cells tend to have a relatively rapid rate of firing, and are either unaffected, or depressed by anesthesia.