Double-dissociation of D1 and opioid receptor antagonism effects on the acquisition of sucrose-conditioned flavor preferences in BALB/c and SWR mice

Abstract

Sugar appetite is influenced by unlearned attractions to sweet taste and learned responses to sugars’ taste and post-ingestive actions. In rats, sugar-conditioned flavor preferences (CFP) are attenuated by dopamine D1 (SCH23390: SCH), but not opioid (naltrexone: NTX), receptor antagonism. Sucrose-CFP occurs in BALB/c and SWR inbred mice that differ in their suppressive effects of SCH and NTX on sucrose intake. The present study examined whether SCH and NTX altered expression of a previously learned sucrose-CFP and acquisition (learning) of sucrose-CFP in these strains. In Experiment 1, food-restricted mice were trained (10 one-bottle sessions) to drink a more-preferred flavored (e.g., cherry) 16% sucrose solution (CS+/Sucrose) on odd-numbered days, and a less-preferred flavored (e.g., grape) 0.05% saccharin solution (CS−/Saccharin) on even-numbered days. Two-bottle tests with the flavors mixed in 0.2% saccharin occurred 30 min following vehicle (Veh), SCH (50–800 nmol/kg) or NTX (1–5 mg/kg) assessing preference expression. CS+ preference expression in BALB/c and SWR mice following Veh were significantly reduced by SCH and NTX. In Experiment 2, separate groups of BALB/c and SWR mice received Veh, SCH (50 nmol/kg) or NTX (1 mg/kg) injections 30 min prior to daily one-bottle training sessions with the CS+/Sucrose and CS−/Saccharin solutions assessing preference acquisition. Subsequent two-bottle tests with the CS+ vs. CS− solutions were conducted without injections. CS+/Sucrose training intakes were reduced by SCH in both strains and by NTX in BALB/c mice. In the initial two-bottle test, sucrose-CFP acquisition was significantly reduced in BALB NTX (54%), but not in BALB SCH (77%) groups relative to the BALB Veh group (85%). In contrast, sucrose-CFP acquisition was significantly reduced in SWR SCH (61%), but not in SWR NTX (83%) groups relative to the SWR Veh group (86%). DA D1 and opioid receptor signaling modulate acquisition and/or expression of sucrose-CFP in mice with significant strain differences observed.

Decreased rates of operant food self-administration are associated with reward deficits in high-fat feeding mice

“…During testing, mice had the same dietary regime, but they had the option between regular tap water and either sucrose (1 %) or saccharine (0.05 %) solutions, presented in graduated 100-mL glass bottles with a drinking well that extended 4 cm into the cage. Concentrations of sucrose and saccharin were chosen following the ones used by other authors [29][30][31][32]. Bottles were placed symmetrically on the food container, and they were switched every day to avoid position preference.…”

Dopamine D1 and opioid receptor antagonist-induced reductions of fructose and saccharin intake in BALB/c and SWR inbred mice

“…Whereas sucrose-CFP expression in both BALB/c and SWR mice was significantly reduced by SCH and NTX, sucrose-CFP acquisition was significantly reduced by NTX, but not SCH in BALB/c mice, and by SCH, but not NTX in SWR mice (Dym et al, 2012). A subsequent study (Kraft et al, 2013) demonstrated that these strains displayed fat (Intralipid)-CFP, and that its acquisition and expression were significantly reduced by SCH and NTX in BALB/c mice, but only by SCH in SWR mice.…”

“…Two of these inbred strains, SWR and BALB/c mice, displayed the most robust and durable sucrose-CFP (Pinhas et al, 2012) and thus Pharmacology, Biochemistry and Behavior 131 (2015) 13-18 were evaluated for DA D1 and opioid antagonist mediation of the expression and acquisition of sucrose-CFP (Dym et al, 2012). Whereas sucrose-CFP expression in both BALB/c and SWR mice was significantly reduced by SCH and NTX, sucrose-CFP acquisition was significantly reduced by NTX, but not SCH in BALB/c mice, and by SCH, but not NTX in SWR mice (Dym et al, 2012).…”

NMDA receptor antagonism differentially reduces acquisition and expression of sucrose- and fructose-conditioned flavor preferences in BALB/c and SWR mice

“…In contrast, opioid receptor antagonism with naltrexone failed to affect the acquisition or expression of CFPs in rats produced by IG sucrose or orally-consumed fructose (Azzara et al, 2000;Baker et al, 2004). Studies of SWR and BALB/c mice revealed that the expression of a CFP produced by oral sucrose was attenuated by both DA D1-like and opioid antagonists (Dym et al, 2012). In contrast, acquisition of sucrose-CFP was reduced by opioid, but not DA D1 antagonism in BALB/c mice, and by DA D1, but not opioid antagonism in SWR mice, indicating a double dissociation in the pharmacological effects on sucrose-CFP in the two strains (Dym et al, 2012).…”

“…Studies of SWR and BALB/c mice revealed that the expression of a CFP produced by oral sucrose was attenuated by both DA D1-like and opioid antagonists (Dym et al, 2012). In contrast, acquisition of sucrose-CFP was reduced by opioid, but not DA D1 antagonism in BALB/c mice, and by DA D1, but not opioid antagonism in SWR mice, indicating a double dissociation in the pharmacological effects on sucrose-CFP in the two strains (Dym et al, 2012). A different pattern of drug effects were observed in mice trained with oral fructose (Kraft et al, 2015).…”