Figure 4.

Diagram illustrating the hypothesized connectivity by which lateral preoptic area (LPO) activation produces activation of mesoaccumbal dopaminergic neurotransmission and accompanying locomotor activation. Panel (a) illustrates a slightly upward tilted sagittal section through the rat brain showing the location of the rostromedial tegmental nucleus (RMTg) and ventral tegmental area (VTA) in relation to numerous other brain structures. Panel (b) is an enlargement of the boxed area in panel (a) showing the hypothesized circuitry. A branched GABAergic projection (red line) from the LPO contacts a GABAergic neuron (red dot) in the RMTg and a postulated GABAergic neuron in the VTA (red circle), which have axons (red lines) that converge to contact a dopaminergic neuron in the VTA (green dot and line) that projects to the accumbens (Acb). Activation of the LPO GABAergic axon inhibits the convergent inhibitory projections from the RMTg and VTA to the dopaminergic neuron. The blue line depicts a glutamatergic projection from the lateral habenula (LHb) to the RMTg, which would drive an inhibition of the dopaminergic VTA neuron. ac, anterior commissure; BLA, basolateral amygdala; Cbl, cerebellum; CeA, central nucleus of the amygdala; CPu, caudate-putamen; Cx, cerebral cortex; DR, dorsal raphe nucleus; fx, fornix; Hip, hippocampus; PPTg, pedunculopontine tegmental nucleus; Tu, olfactory tubercle; VP, ventral pallidum; xSCP, decussation of the superior cerebellar peduncle.