Caffeine down-regulates beta adrenoreceptors in rat forebrain.

We studied the influence of caffeine treatment (50 mg/kg for 3 doses) on catecholamine utilization and adrenergic receptor binding in female rats. Caffeine enhanced the reduction in forebrain norepinephrine levels following alpha-methyl-p-tyrosine without altering the reduction in dopamine levels. Caffeine reduced the apparent number of beta receptors in forebrain as measured by the Bmax for [3H]dihydroalprenolol binding. No changes in alpha1 or alpha2 receptor binding, as measured with [3H]prazosin and [3H]clonidine, respectively, were noted. These data show that caffeine selectively increases the rate of norepinephrine utilization in rat forebrain and that this is associated with a small, but significant, reduction in beta receptor density in this brain area.