The in vivo binding of [3H]-desipramine and [3H]-chlorpromazine to areas in the rat brain.

The distribution of [3H]-desipramine (DMI) and of [3H]-chlorpromazine (CPZ) in rat brain was determined by the incorporation of radioactivity into various regions of the brain and by autoradiography of transverse cryostat sections. The label from [3H]-DMI was rapidly distributed in all brain regions, reaching peak levels within 30 min and considerably decreasing 1--4 h after injection. Following the selective destruction of catecholaminergic nerve terminals by intracerebral administration of 6-hydroxydopamine, a marked reduction in the incorporation of DMI, but not of CPZ, was evident in all brain areas investigated. The autoradiographed sections clearly demonstrated a preferential uptake of both drugs by the caudate nucleus. These findings suggest that DMI might be largely bound to presynaptic dopamine and norepinephrine terminals, while the CPZ binding involves postsynaptic sites.