Effects of AMPA/kainate receptor blockade on responses to dopamine receptor agonists in the core and shell of the rat nucleus accumbens

Abstract 

The present experiments were conducted to investigate effects of α-amino-3-hydroxy-5-methyl-4-isoxazoleprionic acid (AMPA)/kainate receptor blockade (CNQX, NBQX) on locomotor responses to D2/3 (7-OH-DPAT) and D1 [(+)-SKF 38393] dopamine receptor agonists in the nucleus accumbens (NAS) core and shell. CNQX (0.25–0.5 µg) microinjected into the NAS core or shell did not affect baseline locomotor activity. 7-OH-DPAT (2.5–5 µg) decreased locomotor activity. Co- administration of CNQX (0.5 µg) increased the effects of 7-OH-DPAT (5 µg) in the NAS core and shell. A similar increase was observed with NBQX (0.5 µg) in the NAS shell. (+)-SKF 38393 (5 µg) into the NAS core and shell increased locomotor activity after 30 min; this effect was not altered by CNQX (0.5 µg). As the D2/3 dopamine agonist (–)-quinpirole (2 µg) increased effects of (+)-SKF 38393 (5 µg) in NAS shell but not core, lack of site-selective effects of (+)-SKF-38393 and of 7-OH-DPAT within NAS is not attributable to drug diffusion. The previous observation that glutamate effects on locomotor activity depend on the relative involvement of D1 or D2/3 dopamine receptors in the NAS was based on the dopamine-depletion model. The present results demonstrate differential interactions of AMPA receptor blockade with dopamine agonists in ”dopamine-intact” animals.