The rostromedial tegmental nucleus (RMTg), a GABAergic afferent to midbrain dopamine neurons, encodes aversive stimuli and inhibits motor responses.

GABAergic inputs to the VTA come from a list of regions including substantia nigra pars reticulata, nucleus accumbens, ventral pallidum/globus pallidus, laterodorsal tegmentum, pedunculopontine nuclei, diagonal band of Broca, bed nucleus of the stria terminalis, and rostromedial tegmental nucleus.

“GABAergic inputs arrive at the VTA from the substantia nigra pars reticulata, nucleus accumbens, ventral pallidum/globus pallidus, laterodorsal tegmentum, pedunculopontine nuclei, diagonal band of Broca, bed nucleus of the stria terminalis, and the caudal tip of the VTA, termed the rostromedial tegmental nucleus (RMTg) (Geisler and Zahm 2005; Jhou et al. 2009; Kaufling et al. 2009).”

Based on current knowledge, likely pathways for VLPAG outputs are that they may relay in the rostral ventral medulla to modulate premotor neurons that project to the spinal cord, or they may relay in the rostral ventral midbrain onto dopaminergic neurons of the substantia nigra; in either case, those neurons would modulate motor loops in the striatum, producing immobility.

“Based on current knowledge, the likely pathways for VLPAG outputs are as follows: the outputs may relay in the rostral ventral medulla to modulate premotor neurons that project to the spinal cord, or they may relay in the rostral ventral midbrain onto dopaminergic neurons of the substantia nigra; in either case, those neurons would modulate, in turn, motor loops in the striatum (basal ganglia),”

The LHb projects densely to the RMTg and has a well-established inhibitory effect on midbrain DA neuron firing.

“In particular, the LHb projects densely to the rostromedial tegmental nucleus (RMTg) (Jhou et al. 2009), and has a well-established inhibitory effect on the firing of midbrain DA neurons (Lecourtier and Kelly 2007;Matsumoto and Hikosaka 2009;Hikosaka 2010;Bromberg-Martin and Hikosaka 2011).”

Changes in DAergic activity can signal punishment, aversion, or lack of expected reward, not only hedonic effects.

“Although it was originally postulated that the DA released from the VTA only mediates the hedonic or pleasurable effects of natural reinforcers, it is now clear that changes in DAergic activity can also signal punishment, aversion, or lack of expected reward [53–58].”

Neurons in the rostromedial tegmental nucleus, which receive a major input from the lateral habenula, project to VTA DA neurons and are activated after food deprivation.

“Moreover, neurons in the rostromedial tegmental nucleus, which receive a major input from the lateral habenula, project to VTA DA neurons and are activated after food deprivation (158).”

Neurons in the rostromedial tegmental nucleus receive major input from the lateral habenula, project to VTA dopamine neurons, and are activated after food deprivation.

“The habenula is also implicated in food reward: neurons in the rostromedial tegmental nucleus, which receive a major input from the lateral habenula, project to VTA DA neurons and are activated after food deprivation (110).”

Neurons in the rostromedial tegmental nucleus, which receive a major input from the lateral habenula, project to VTA DA neurons and are activated after food deprivation.

“neurons in the rostromedial tegmental nucleus, which receive a major input from the lateral habenula, project to VTA DA neurons and are activated after food deprivation (Jhou et al 2009)”