Respective roles of dopamine D2 and D3 receptors in food-seeking behaviour in rats

Abstract

These results indicate that reinstatement of non-reinforced responding by non-contingent food delivery and by dopamine agonists probably depend on different mechanisms. The properties of D(2)/D(3) receptor agonists, to reinstate food seeking at larger doses, and to potentiate food-primed response reinstatement at lower doses, are preferentially mediated by D(2) rather than by D(3) receptors.

Effects of a Dopamine D3 Receptor Ligand, BP 897, on Acquisition and Expression of Food-, Morphine-, and Cocaine-induced Conditioned Place Preference, and Food-seeking Behavior in Rats

“…Such a priming effect, initially observed with drugs, has been proposed as an operational measure of seeking behavior, that is, enhanced motivation for the reinforcer (Carroll and Comer, 1996;Meil and See, 1996;Shalev et al, 2002). Drugand food-priming effects can be differentially modulated by dopaminergic drugs (Self et al, 1996;Khroyan et al, 2000;Alleweireldt et al, 2002;Vorel et al, 2002;Duarte et al, 2003). However, the present study shows that over a large range of doses, BP 897 did not interfere with the reinstating effect of food priming.…”

“…In the reinstatement procedure of extinguished response for food, the noncontingent delivery of two food pellets during the extinction component resulted in a modest recovery of nonrewarded response, as already reported (McFarland and Kalivas, 2001;Duarte et al, 2003). Such a priming effect, initially observed with drugs, has been proposed as an operational measure of seeking behavior, that is, enhanced motivation for the reinforcer (Carroll and Comer, 1996;Meil and See, 1996;Shalev et al, 2002).…”

“…Previous results indicated that nafadotride was also ineffective, whereas low doses of 7-OH-DPAT and quinelorane potentiated food-primed food-seeking responses. The latter effect, which disappeared at larger doses, has been related to a preferential activation of D 3 R, although an involvement of D 2 R cannot be ruled out (Duarte et al, 2003). Thus, distinct to full agonists, BP 897 did not interact with the dopaminergic processes triggered by the unexpected delivery of food and its consumption, which are responsible for food-seeking behavior.…”

“…In contrast, neither the establishment nor the expression of food-and morphine-CPP were significantly altered by BP 897 (up to 1 mg/kg), whereas the full but less selective D 3 /D 2 R agonists, 7-OH-DPAT (0.5-2 mg/kg, s.c.) and quinelorane (1 mg/kg, s.c.), prevented the acquisition of food CPP. In a within-session extinction schedule of lever pressing for food, BP 897 (0.06-2 mg/kg) was ineffective in potentiating response reinstatement induced by the noncontingent delivery of two food pellets, in contrast with quinelorane and 7-OH-DPAT where previous studies showed to be efficient in this respect (Duarte et al, 2003). These results indicate that BP 897 has no positive appetitive value on its own, and that a moderate degree of stimulation of D 3 R is not sufficient to modulate food-primed food-seeking behavior or alter incentive motivation for food, morphine, and/or their associated cues.…”

“…The experiments were performed using food-restricted rats (13 g/day/rat) as previously described (Duarte et al, 2003). Briefly, the animals were trained to press the right lever according to a fixed ratio 1 (FR 1 ) schedule of food delivery (45 mg pellets, F 0165, Bioserv, Frenchtown, NJ, USA).…”