Dexmedetomidine decreases extracellular dopamine concentrations in the ratnucleus accumbens

The effects of dexmedetomidine, a highly selective alpha (2)-adrenoceptor a gonist, on extracellular dopamine (DA) concentrations in the nucleus accumb ens of awake rats were collected via in vivo cerebral microdialysis and mea sured using HPLC with electrochemical detection. The administration of dexm edetomidine (DEX) at a low dose (2 mug/kg bolus i.v. over 2 min followed by a continuous infusion of 0.1 mug/kg per min) and a high dose (20 mug/kg bo lus i.v. over 2 min followed by a continuous infusion of 1 mug/kg per min), significantly decreased extracellular dopamine, concentrations in the nucl eus accumbens. The observed decrease was dose-dependent, occurring sooner a nd to a greater magnitude in the rats receiving a high dose of DEX. This in hibitory modulation of accumbal dopamine was receptor-specific, as the decr ease in extracellular DA produced by DEX was no longer evident following pr e-treatment and co-infusion with the highly selective alpha (2)-adrenocepto r antagonist, atipamezole (ATZ). Thus, these data suggest that adrenoceptor agonists and antagonists may modulate dopaminergic neurotransmission via m echanisms that are specific to the alpha (2)-adrenoceptor. (C) 2001 Elsevie r Science B.V. All rights reserved.