Response of mesolimbic substance P systems to methamphetamine treatment.

Administration of methamphetamine (METH) has been shown to increase substance P (SP) concentrations in striatonigral structures. Data described herein demonstrate that SP pathways associated with the mesolimbic systems also are influenced by METH treatment. Specifically, multiple doses of METH significantly decreased SP concentrations in the ventral tegmental area and the medial habenular nucleus; whereas, a single METH injection increased the levels of this neuropeptide in the ventral tegmental area. The possible significance of these observations is discussed.