Figure 2. The stimulant effect of caffeine on locomotion is dose-dependent. Animals received increasing acute intravenous injections of 1-10 mg caffeine/kg body wt 15 min before the onset of the [¹⁴C] 2-deoxyglucose procedure. The local cerebral metabolic rate for glucose (LCMR_glc) was measured in regions of the nigrostriatal dopaminergic system: substantia nigra pars compacta (SNPC), dorsomedial caudate nucleus (DMCAU), globus pallidus (GPAL), and sensorimotor cortex (SMCX). *p < 0.05 and **p < 0.01, statistically significant differences from controls, as determined by Dunnett's t-test for multiple comparisons.