Daily bupropion injections for 3 weeks attenuate the NE stimulation of adenylate cyclase and the number of beta-adrenergic recognition sites in rat frontal cortex.

In rats receiving daily doses (50 mg/kg i.p. twice daily) of bupropion HCI (WellbutrinR) repeated for 21 days the Bmax of the beta-adrenergic receptor recognition sites located in the frontal cortex is reduced. This decrease is not associated with a decrease of the apparent affinity of these recognition sites. However the Vmax of the cAMP (cyclic AMP) generating system stimulated by NE is reduced suggesting that similarly to other antidepressants bupropion down regulates beta-adrenergic receptors located in the frontal cortex. Bupropion neither inhibits MAO (monoamine oxidase) nor releases biogenic amines but only weakly inhibits monoamine uptake in vitro.