The Tail of the Ventral Tegmental Area/Rostromedial Tegmental Nucleus: A Modulator of Midbrain Dopamine Systems

The tail of the ventral tegmental area (tVTA) or rostromedial tegmental nucleus (RMTg) is a recently described brainstem group of gamma-amino butyric acid cells that densely innervate the VTA and the substantia nigra pars compacta, exerting tonic and phasic inhibitory control over the activity of dopamine cells. The molecular impact of psychostimulants on the tVTA/RMTg, the expression of µ-opioid receptors in these neurons, and the dense input from the lateral habenula, together with the brake activity exerted on dopamine systems, are fostering research on tVTA/RMTg functions. This nucleus has already been shown to encode prediction error, control freezing behavior and locomotor activity, influence motor coordination performance and motor skill learning, promote avoidance behaviors, participate in responses to aversive stimuli and drugs of abuse, and to be a key structure for opioid-induced disinhibition of dopamine neurons. This chapter details the current physiological and behavioral knowledge on the tVTA/RMTg.