Paroxetine pretreatment does not change the effects induced in the rat cortical β-adrenergic receptor system by repetitive transcranial magnetic stimulation and electroconvulsive shock

Abstract

Repetitive transcranial magnetic stimulation (rTMS) has been proposed as a clinically effective antidepressant treatment, but meta-analysis suggests that its efficacy is marginal. We investigated whether the administration of rTMS together with paroxetine would enhance its effects on the beta-adrenergic system of the rat. We compared our results with the effects of electroconvulsive shock therapy (ECS). The experiment was performed for 12 d on male Wistar rats that received a physical treatment of either rTMS (B=1.4 T, f=10 Hz, 300 s) or ECS (I=130 mA, f=50 Hz, t=500 ms), preceded by sterile water or paroxetine (10 mg/kg i.p. 30 min earlier). All rats were decapitated 24 h after the final treatment. Cyclic AMP (cAMP) was measured in cortical slices prelabelled with [3H]adenine and stimulated with noradrenaline. beta-adrenoceptor parameters (Bmax and KD) were assessed in the P2 fraction of cortical homogenates using [3H]CGP 12177 as a ligand. ECS resulted in down-regulation of both the cAMP response and beta-adrenoceptor density, while rTMS depressed only the responsiveness of the cAMP-generating system. Paroxetine, which was only effective in dampening the cAMP response, did not change the effects of either physical treatment. The data suggest that any possible interaction between paroxetine and rTMS or ECS does not involve the beta-adrenergic mechanisms.