Mesolimbic dopaminergic mechanisms underlying individual differences in sugar consumption and amphetamine hyperlocomotion in Wistar rats

Abstract

Individual differences within strains of rats have been demonstrated for dopamine-mediated behaviours and responses to dopaminergic drugs. Differences in mesolimbic dopamine function may underlie individual differences in some of these behaviours, including sugar consumption and amphetamine hyperlocomotion. The present study addressed two potential mechanisms for these differences in dopamine-mediated behaviours. The possibility of functional differences in dopamine receptor subtypes was tested in LOW and HIGH sugar feeders. LOW and HIGH feeders did not differ in their response to the partial D1 agonist SKF-38393. The highest dose (2.5 mg/kg) of the D2 agonist quinpirole stimulated locomotor activity to a greater degree in a subset of HIGH sugar feeders as compared with LOW feeders. All doses of amphetamine induced a greater locomotor response in HIGH feeders as compared with LOW feeders, and HIGH feeders exhibited higher levels of extracellular dopamine in the nucleus accumbens than LOW feeders following exposure to sugar and treatment with amphetamine. These results support the interpretation that LOW and HIGH feeders exhibit differences in presynaptic nucleus accumbens dopamine function that account for the expression of individual differences in sugar consumption and response to amphetamine treatments. A subset of HIGH feeders may also exhibit greater D2 receptor function.

Sucrose intake predicts rate of acquisition of cocaine self-administration

“…This finding parallels reports that amphetamine caused a greater locomotor response and a greater increase in extracellular dopamine in the nucleus accumbens in high sugar feeders than in low sugar feeders (Sills and Vaccarino 1994;Sills and Crawley 1996). When microdialysis samples were collected during access to sucrose, high sugar feeders consumed more sucrose than low feeders and showed an increase above baseline in extracellular dopamine in the nucleus accumbens; dopamine levels in the accumbens of low sucrose feeders did not increase above baseline (Sills et al 1998).…”

“…injection of 0.9% saline) (Sills and Vaccarino 1994;Sills and Crawley 1996;Sills et al 1998). It has been suggested that the differences observed between high and low sucrose feeders in response to amphetamine may actually be due to differences in stress sensitivity (Sills and Vaccarino 1994).…”

“…It is well established that cocaine and amphetamine cause an increase in extracellular dopamine in the nucleus accumbens (Di Chiara and Imperato 1988), and there are now many reports that increases in dopamine release are also observed during and/or after the consumption of food or palatable fluid (Mark et al 1991;Yoshida et al 1992;Westerink et al 1994;Wilson et al 1995). Sills et al (1998) have shown that both amphet-290 amine treatment and sucrose feeding evoke a larger increase in accumbens dopamine release in high sucrose feeders than in low sucrose feeders. However, the amount of sucrose consumed during the microdialysis sessions was not controlled, such that the high sucrose feeders consumed more than the low sucrose feeders.…”

The melanocortin receptor agonist MTII augments the rewarding effect of amphetamine in ad-libitum-fed and food-restricted rats

“…This phenomenon parallels the enhancement, by food restriction, of drug self-administration (Carroll and Meisch 1984) and conditioned place preference (Bell et al 1997), and appears to reflect an increase in sensitivity of the neural substrate for drug reward (Cabeza de Vaca and Carr 1998). The augmentation of drug reward by food restriction is just one of numerous observations that support an association between drug-seeking and ingestive behavior (Sills et al 1998;Gosnell et al 1995;Comer et al 1996;Sills and Vaccarino 1994;Gosnell 2000). Although the physiological mechanisms underlying the augmentation of drug reward by food restriction have not been established, the augmented rewarding effect of amphetamine in food-restricted subjects is associated with increased cfos expression in limbic forebrain dopamine terminal areas (Carr and Kutchukhidze 2000).…”

Differential Effects of Dopamine Receptor D1-Type and D2-Type Antagonists and Phase of the Estrous Cycle on Social Learning of Food Preferences, Feeding, and Social Interactions in Mice

“…Dopamine (DA) has been implicated in various types of learning, likely through actions on synaptic plasticity (Calabresi et al, 2007) and/or motivation (Wise, 2006). Acting through its D1-type (D1 and D5) and D2-type (D2, D3, and D4) receptors, DA mediates learning about novel flavors and spontaneous flavor preferences Cooper, 1988, 1989;Sills et al, 1998), such that the two DA receptor (DAR) types are similarly involved in the former, but affect the latter differently (Rusk and Cooper, 1988, 1994Yu et al, 2000a, b;Baker et al, 2003;Cooper and Al-Naser, 2006).…”