Distribution of the beta-2 adrenergic receptor messenger RNA in the rat brain by in situ hybridization histochemistry: effects of chronic reserpine treatment.

We studied the distribution of the rat brain beta-2 adrenergic receptor (AR) mRNA, and the effects of monoamine depletions by chronic reserpine treatment using in situ hybridization histochemistry. In the control group, high level signals of beta-2 AR mRNA were observed in the parietal, frontal and piriform cortices, the medial septal nuclei, the olfactory tubercle, and the midbrain. Moderate signals were found in the striatum, the retrosplenial cortex, the hippocampus, and the thalamic nuclei. After chronic reserpine treatment, beta-2 AR mRNA levels were increased in many brain regions. The large increases were seen in the hippocampus, all thalamic nuclei, the amygdaloid nuclei, and the midbrain, followed by the striatum and the occipital cortex. The receptor up-regulation resulting from chronic monoamine depletion may be due to these increases in beta-2 AR mRNA, indicating that this up-regulation may be caused by increased receptor production rather than decreased receptor degradation.