Synergistic, but not separate, stimulation of accumbal beta1- and beta2-adrenoceptors alters the accumbal dopamine efflux in freely moving rats

Item does not contain fulltext The effects of intra-accumbal infusion of selective agonists for the beta-adrenoceptor subtypes on the noradrenaline and dopamine efflux in the nucleus accumbens of freely moving rats were investigated, using in vivo microdialysis. Neither beta1-(dobutamine: 0.06 and 0.12 pmol) nor beta2-adrenoceptor agonist (salbutamol: 0.36 and 3.6 pmol) altered the basal noradrenaline and dopamine efflux in the nucleus accumbens. Co-administration of 0.06 pmol of dobutamine with salbutamol (3.6 pmol) did not affect the noradrenaline levels, but it increased the dopamine efflux to approximately 120%. Co-administration of 0.12 pmol of dobutamine with salbutamol (0.36 or 3.6pmol) also increased DA efflux to approximately 120% without affecting noradrenaline levels. The non-selective beta-adrenoceptor antagonist l-propranolol (1200 pmol) that did not alter the basal noradrenaline and dopamine levels, suppressed the dopamine efflux, induced by co-administration of dobutamine (0.12 pmol) and salbutamol (3.6 pmol). The doses mentioned are the total amount of drug over the 60-min infusion period. The present results support our previously reported conclusion that stimulation of accumbal beta-adrenoceptors which are suggested to be postsynaptically located on accumbal dopaminergic terminals, can enhance the dopamine efflux in the nucleus accumbens. The present study also provides in vivo neurochemical evidence that concomitant, but not separate, activation of accumbal beta1- and beta2-adrenoceptors synergistically increases the accumbal dopamine efflux.