Evidence for a role of the shell of the nucleus accumbens in oral behavior of freely moving rats

Abstract

Behavioraleffects of intra-accumbens administration of the dopamine DA, receptor agonist (3,4-dihydroxyphenylimino)-2-imidazoline (DPI) were studied in freely moving rats. Three distinct areas were examined: core, shell and "shore," namely, the border region of the core and shell. DPI (5 pg) administered into the shell, but not areas ventral to the shell, increased chewing, tongue protrusion, sniffing, and grooming; it also induced abnormal oral behavior, namely, largeamplitude chewing.A similar dose of DPI administered into the core did not affect any (peri-)oral behavior, except sniffing. Because of methodological constraints the receptor specificity of the DPI effects was studied in rats with cannulas directed at the shore. DPI (5.0-l 0.0 pg) administered into the shore increased oral behavior dose dependently; however, the dose-effect curve varied per distinct type of oral behavior. The dopamine DA, receptor antagonist ergometrine attenuated the effect of DPI on tremor, chewing, and sniffing frequencies.Taken together, the data show that the effects of DPI were DA, receptor specific. The idea that the nucleus accumbens is a homogeneous structure is disappearing. During the last 10 years differences have been found between core and shell with respect to anatomy (Zaborsky et al., 1985; Voorn et al., 1989; Heimer et al., 1991;Berendse et al., 1992;Zahm and Brog, 1992; and others), receptor density (Bardo and Hammer, 199 l), pharmacology (Deutch and Cameron, 1992), and electrophysiology (Pennartz et al., 1992). Still, with respect to behavior of freely moving rats, no studies on differences between core and shell have been performed. Therefore, the aim of this study was to analyze the role of different parts of the nucleus accumbens in modulating behavior. The nucleus accumbens modulates oral behavior in rats (Bordi et al., 1989;Cools, 1990;Koshikawa et al., 1990 Koshikawa et al., , 1991Prinssen et al., 1992; Koene et al., 1993). It has been found that intra-accumbens administration of the dopamine DA, receptor Received Mar. 11, 1993; revised July 1, 1993; accepted Aug. 26, 1993. We express our gratitude to Dick Heeren for his valuable support with programming, and to Luuk Lubbers for the learning of operation techniques. agonist (3,4-dihydroxyphenylimino)-2-imidazoline (DPI) increases oral behavior in rats (Cools, 1990). In cats, the same drug (DPI) has been found to induce abnormal oral movements, namely, orofacial dyskinesias (OFD), when administered into a well-delineated striatal subarea (Cools et al., 1976; Spooren et al., 199 1). Accordingly, DPI was considered to be a valid tool to study the putative, differential involvement of the core and shell of the nucleus accumbens in oral behavior of freely moving rats. In the present investigation the behavioral effects of DPI injections into the core were compared with those elicited by DPI injections into the shell. The outcome of this study shows that administration of DPI (5 Kg) into the shell, but not the core, increased and induced oral behaviors. How...

Role of dopamine D1 and D2 receptors in the nucleus accumbens in jaw movements of rats: a critical role of the shell

“…The outcome of the present study confirms the earlier reported finding that the shell, but not the core, of the nucleus accumbens is involved in the control of oral behaviour, especially jaw movements (Borcli et al, 1989;Cools et al, 1993;Prinssen et al, 1994): the combined administration of SKF 82985 and quinpiroie was only effective when injected into the shell, but not the core, of the nucleus accumbens. The finding that especially the shell of the nucleus accumbens is in volved in oral behaviour is understandable in view of the fact that the shell projects to a part of the ventral pallidum, that is known to be involved in oral be haviour (Spooren et al, 1989).…”

“…The registration period lasted 240 min. Guide cannulas were implanted bilater ally into the shell or into the core of the nucleus accumbens according to previously described proce dures (Prinssen et al, 1994). The coordinates based on the atlas of Paxinos and Watson (1986) were: anterior = 10.6 mm, lateral = 0.5 mm, vertical = 8.0 mm (shell); anterior = 10.6 mm, lateral = 1.2 mm, ventral = 7.0 m m (core).…”

“…In addition, recent studies on oral behaviour suggest that especially the shell plays a critical role as neuroanatomical substrate for oral behaviour (Cools et ah, 1993;Prinssen et al, 1994).…”

d-Sulpiride inhibits oral behaviour elicited from the nucleus accumbens of freely moving rats

“…effects (cf. [22]) rather than to a lack of effect of ¿/-sulpiride, which ncmsignificantly attenuated all these oral behaviors (data not shown).…”

“…The procedure is described elsewhere in detail [22]. After sur gery the rats were housed individually in the original stockroom and allowed recovery from operation for at least 1 week.…”