Differential distribution of methamphetamine to brain and heart tissues after intravenous administration. Changes in methamphetamine (METH) concentration in rostral ventrolateral medulla (RVLM), caudal ventrolateral medulla (CVLM), nucleus tractus solitarii (NTS), nucleus accumbens (NACC), globus pallidas (GPi), caudate nucleus (Cd), substantia nigra (SN), ventral tegmental area (VTA) or heart (H) collected from rats 20 min (gray bar) or 240 min (hatched bars) after intravenous administration of METH at 12 mg/kg (M12) or 24 mg/kg (M24). Values are mean ± SEM, n = 4-6 animals per experimental group. Red dotted line represents the mean value of METH concentration in RVLM, CVLM and NTS and blue dotted line represents the mean value of METH concentration in NACC, GPi, Cd, SN and VTA. Whereas#P < 0.05 versus heart tissue exists in all four subsets, it is only denoted in one subset for clarity. *P < 0.05 versus 20 min group at corresponding dose, and+P < 0.05 versus M12 group at corresponding time-points in the post hoc Scheffé multiple-range test.