Abstract
We used the autoradiographic 2-deoxy-D-[1-14C]glucose (14C-DG) method of Sokoloff to identify brain areas with altered rates of local cerebral glucose utilization (LCGU) in vivo in response to peripheral I-nicotine administration (0.1, 0.3, 1.0, and 1.75 mg/kg, s.c.). Nicotine stimulated LCGU primarily in areas reported to contain nicotine binding sites, indicating that the sites are true receptors. Increases in LCGU of 100% or more over control were obtained in the medial habenula, fasciculus retroflexus, superior colliculus, and median eminence. Substantial stimulation (50-100% increases) also was obtained in the cerebellar vermis, interpeduncular nucleus, and anteroventral and interanteromedial thalamic nuclei. Moderate increases (20-50%) were observed in the reticular nucleus of the medulla, paramedian lobule, nucleus of the spinal tract of the trigeminal nerve, presubiculum, subiculum, red nucleus, ventral tegmental area, substantia nigra, nucleus ambiguus, nucleus tractus solitarius, dorsal lateral geniculate nucleus, mammillothalamic tract, and fornix. The greatest stimulation in most affected areas was obtained with 0.3 mg/kg nicotine administered at 2 min, but not longer, before 14C-DG. Effects of nicotine on LCGU were antagonized by mecamylamine. The findings indicate that the interaction of nicotine with specific binding sites is coupled to cerebral energy metabolism. The distribution of in vivo cerebral metabolic effects of nicotine implicates various brain regions in the behavioral and physiological effects of nicotine.