Effects of dopamine D1 and D2 receptor agonists on environmental enrichment attenuated sucrose cue reactivity in rats

Abstract

Rationale Acute or chronic environmental enrichment (EE) reduces sucrose cue reactivity in rats. This effect may be mediated by dopamine receptors. Objectives We examined whether dopamine D1 or D2 receptor agonism could reverse the EE effect. We also examined whether any reversal effects would vary with the incubation of sucrose craving. Methods Following 10 days (2 h/day) of sucrose self-administration, rats experienced either 1 or 30 days of forced abstinence and either overnight (acute) or 29 day (chronic) EE. D1 (SKF 81297; 0, 0.3, or 1 mg/kg) or D2 (quinpirole; 0, 0.1, or 0.3 mg/kg) agonist was administered systemically immediately prior to a subsequent 2-h cue reactivity test the next day (n = 9–12 per group). Results Dose-dependent effects were limited to the day 1 test. High doses of the agonists increased day 1 acute EE cue reactivity to levels comparable to control animals. On the day 30 test, SKF 81297 increased cue reactivity in acute EE, chronic EE, and control rats. In contrast, quinpirole resulted in similar cue reactivity for control and enriched rats, more from a reduction in responding by controls vs. a recovery of responding by EE-experienced rats. Conclusions Both D1 and D2 receptors may be involved in the acute EE-mediated decrease in cue reactivity observed following 1 day of forced abstinence. In contrast, at 30 days of forced abstinence, D1 receptors may be critical in cue reactivity as SKF 81297 was effective at both restoring responding of enriched animals and potentiating responding of controls.

Incubation of food craving in rats: A review

“…These results indicate that dopamine signaling specific to behavior directed towards a sucrose cue is altered during protracted abstinence. This is supported by our subsequent finding of an abstinence-dependent increase in dopamine D1 agonist-enhanced sucrose craving (Glueck, Ginder, Hyde, North, & Grimm, 2017). The D1 antagonism effect with incubation was not found to be specific to the nucleus accumbens core or shell (mesolimbic dopamine terminals) however (Grimm et al, 2011), indicating that changes in other brain regions and/or neurotransmitter systems mediate incubation of sucrose craving.…”

“…Incubation of sucrose craving is not attenuated by sucrose satiation. This is supported by our subsequent finding of an abstinence-dependent increase in dopamine D1 agonist-enhanced sucrose craving (Glueck, Ginder, Hyde, North, & Grimm, 2017). Either the afternoon of the 10 th day of training, or 29 days later, rats were provided a bottle of 10% sucrose in the home cage until immediately before cue-reactivity testing the next day.…”

Evaluating Time-Dependent Changes in Food Seeking Following Periods of Forced Abstinence and Associated Changes in the Nucleus Accumbens

“…Following 30 days of abstinence, SKF 81297 administration increased cue reactivity in acute EE, chronic EE, and control rats and quinpirole resulted in a similar cue reactivity for both control and EE rats. This suggests that following 30 days of abstinence D1 receptors may be important for cue reactivity (Glueck et al, 2016).…”

“…Time-dependent changes within the NAc have been highlighted in the incubation of craving (Glueck, Ginder, Hyde, North, & Grimm, 2016;Grimm, Harkness, et al, 2011). These changes include alterations in overall neuron activity, DA receptor expression, AMPA receptors, and neuron structure (Christian et al, 2016;Dingess et al, 2017;Grimm et al, 2003;Koya et al, 2009b;Lee et al, 2013;Lu et al, 2005;Terrier et al, 2015).…”

“…Glueck and colleagues (2017) investigated whether the ability of acute and chronic EE to reduce sucrose cue reactivity is mediated by DA receptors (Glueck et al, 2016). The study investigated whether D1 and/or D2 receptor agonism could reverse the EE effect on the incubation of sucrose craving.…”