DIFFERENTIAL BEHAVIORAL-RESPONSES TO DOPAMINERGIC STIMULATION OF NUCLEUS-ACCUMBENS SUBREGIONS IN THE RAT

The following experiments investigated the behavioral response to loca l microinfusion of dopamine (DA) and selective DA agonists into the co re and shell subregions of the nucleus accumbens. Rats were implanted with chronic indwelling cannulae aimed at these subregions. Two experi ments were conducted. In experiment 1, the response to DA (0, 2, 5, 10 mu g/0.5 mu l/side), the D-1 agonist SKF-82598 (0, 0.1, 1.0 mu g), th e D-2/3 agonist quinpirole (0, 1, 5, 15 mu g) and the D-3 preferring a gonist pramipexole (0.1, 1.0, 10.0 mu g) was examined in photocell act ivity cages. Locomotor (horizontal) and rearing (vertical) activities were measured. DA and SKF-82958 induced relatively greater increases i n activity following stimulation of the shell as compared with the cor e. Quinpirole induced a dose-dependent suppression of activity after i nfusion into both sites, although the core was more sensitive to the s uppressive effect than the shell. Pramipexole induced time-dependent, biphasic effects that were small ill magnitude and did not differentia te between site. In experiment 2, an observation procedure was used to record behaviors (locomotion, rearing, feeding, drinking). Dopamine ( 0, 2, 10 mu g) elicited greater increases in rearing and feeding behav ior in the shell than in the core. SKF-82958 (0, 0.75 mu g) enhanced l ocomotion and rearing to a similar extent in both subregions in this t est, whereas a mixture of a low dose (0.25 mu g) of the D-1 and D-2 ag onists selectively induced behavioral activation in the shell. In cont rast to the results in the activity cage test, quinpirole (0, 1, 5 mu g) increased motor activity at the lower dose when infused into the sh ell but not into the core. No alterations in feeding were observed fol lowing infusion of selective agonists, and no changes in drinking were found with any of the treatments. In summary the shell appears to be relatively more sensitive to the motor activating effects of DA agonis ts than the core. Moreover, circuits associated with shell may be pref erentially involved in feeding. (C) 1997 Elsevier Science Inc.