Contralateral turning elicited by unilateral stimulation of dopamine D2 and D1 receptors in the nucleus accumbens of rats is due to stimulation of these receptors in the shell, but not the core, of this nucleus

Abstract

The goal of this study was to determine whether dopamine D 2 and/or Dj receptors in the shell and the core of the nucleus accumbens of rats have a differential role in turning behaviour. Unilateral injec tion of a mixture of the dopamine D2 receptor agonist quinpirole (10 \ig) and the dopamine Di receptor ago nist 1-phenyl-2,3,4,5-tetrahydro-l//-3-benzazepine-7, 8-diol (SKF 38393, 5 jig) into the shell of the nucleus accumbens produced contralateral turning, when doses which per se were ineffective were injected. This effect was far greater than that found after similar injections into the core of the nucleus accumbens. The effect elici-

Role of Dopamine D1and D2Receptors in the Nucleus Accumbens in Mediating Reward

“…The cooperative effect of the SKFϩQuin mixture on intra-accumbens self-infusions is in general agreement with findings on motor activation produced by manipulations of ACB DA or DA receptors. In general, microinjection of either a D 1 or D 2 agonist alone into the ACB had little or no effect on motor activity, whereas concurrent injection of a D 1 and D 2 agonist into the ACB increased motor activity (Plaznik et al, 1989;Essman et al, 1993;Koshikawa et al, 1996a). The heightened locomotor activity produced by concurrent D 1 and D 2 agonists was attenuated by coadministration of either a D 1 or D 2 antagonist (Plaznik et al, 1989;Koshikawa et al, 1996a).…”

“…In the ACB, synergistic effects of D 1 and D 2 agonists have been reported for locomotor activity (Dreher and Jackson, 1989;Essman et al, 1993;Koshikawa et al, 1996a), jaw movements (Cools et al, 1995;Koshikawa et al, 1996b), and neuronal firing (White, 1987). However, there is no clear information whether the interaction of D 1 and D 2 receptors within the ACB can produce a cooperative or synergistic effect on reinforcement processes.…”

Nucleus Accumbens and Dopamine-Mediated Turning Behavior of the Rat: Role of Accumbal Non-dopaminergic Receptors

“…Furthermore, the dopamine D 1 binding in the rostral areas of the Nacc appears to be higher in the shell than in the core, whereas the dopamine D 2 binding appears to be lower in the shell than in the core (11). Thus, it is not remarkable that dopamine functions vary across the core and the shell (15,16). The shell is thought to play a pivotal role in dopamine-mediated functions because it contains the largest amount of dopaminergic terminals and the highest concentration of dopamine (12,13).…”

“…Unilateral activation of the Nacc has been shown to elicit two characteristic types of turning behavior, namely circling and pivoting (16,17). Circling is marked by normal hindlimb stepping, normal forelimb stepping, turns of large diameter (> 30 cm), and running, whereas pivoting is marked by abnormal hindlimb stepping, turns of small diameter (< 20 cm), and spinning around one hindlimb (17).…”

Original article Involvement of D 2 /D 2 dopamine antagonists upon open-arms exploratory behaviours induced by intra-nucleus accumbens shell administration of N-methyl-D-aspartate

“…For example, the D 1 -and D 2 -like dopamine receptor families are higher and lower in the NAc shell than in core, respectively [30]. This may partly explain the different physiological functions of the two parts of NAc [40,42]. Due to the abundant dopaminergic inputs which NAc shell receives from various brain parts and the consequent high contraction level of dopamine in the NAc shell, this part is believed to render a critical role in dopamine-mediated functions [30].…”