Taste and emotionality in rats selectively bred for high versus low saccharin intake

Abstract

Rats were selectively bred for high versus low saccharin ingestion, a putative measure of enhanced stress and emotionality (Dess, 1991). In Experiment 1, third-generation Occidental highsaccharin (HiS) and low-saccharin (LoS) rats were tested for saccharin ingestion and emotionality. The saccharin test confirmed that the lines differed on the selection phenotype. In addition, LoS rats were more emotional, as evidenced by longer emergence latencies and more defecation in a modified open-field test. In Experiment 2, LoS rats had lower quinine preference scores and drank saccharin-adulterated glucose less avidly. These outcomes are reminiscent of the behavior shown by inescapably shocked rats. Unlike helpless rats, however, LoS rats drank less avidly during a dilute sucrose test, an effect more reminiscent of chronic mild stress. The lines did not differ reliably on intake of concentrated glucose or Polycose, even when the latter was mixed with saccharin. In Experiment 3, LoS rats preferred saccharin less strongly than did HiS rats at concentrations of 0.05% to 0.7%and had an aversion to a 1.0% solution. In Experiment 4, LoS rats were affected more by shock, as assessed by stress-induced anorexia. These and other recent findings support the notion of shared mechanisms for taste, emotionality, and stress vulnerability.Ingestion interacts extensively with affective processes, such as fear and distress (Dess, 1991). For instance, exposure to intermittent electric shock alters the distribution of meals and eating rate in a manner suggestive of

Higher locomotor response to cocaine in female (vs. male) rats selectively bred for high (HiS) and low (LoS) saccharin intake

“…According to these procedures, HiS rats showed little or no emotionality; whereas, LoS rats showed high emotionality Minor, 1996, Dess et al, 2000). Differences in emotionality could explain previous reports of HiS/LoS line differences, including ethanol intake (HiS > LoS) (Dess et al, 1998), acquisition of cocaine self-administration (HiS > LoS) , elevated basal (LoS > HiS) and stress-induced (HiS = LoS) CORT levels (VanderWeele et al, 2002), acoustic startle amplitude (LoS > HiS) (VanderWeele et al, 2002), and taste reactivity (HiS > LoS) (Dess and Minor, 1996). Other groups with differing genetic propensities for drug-seeking behavior, such as those bred for high (HR) and low (LR) reactivity to a novel environment show differences in emotionality that are in the same direction (LR > HR) (Stead et al, 2006), highlighting the complex interactions among genetic background, environmental stimuli, and drug effects.…”

“…The HiS and LoS lines had been developed through pairings of rats with extreme HiS and LoS phenotype scores with no sibling, half-sibling, or first-cousin matings according to methods of Dess and Minor (1996). The breeding process, which was initiated at Occidental College (Los Angeles, CA, USA), has been continued in our laboratory at the University of Minnesota since 2002.…”

Intravenous cocaine and heroin self-administration in rats selectively bred for differential saccharin intake: phenotype and sex differences

“…In fact, the characteristic that has been selectively bred may be a general tendency to consume flavored solutions. Differences in emotionality and pain sensitivity have also been linked to ethanol (Badistov et al 1995;Kampov-Polevoy et al 1996;Overstreet et al 1997) and saccharin (Dess and Minor 1996;Dess et al 2000) consumption. There is clearly a genetic influence in bitter and sweet taste sensitivity in humans (Bartoshuk 1979;Gent and Bartoshuk 1983;Bartoshuk et al 1988;Looy and Weingarten 1992), and its relationship to drug abuse (Pelchat and Danowski 1992).…”

“…A goal of the present research was to compare rats from Occidental College (Los Angeles, Calif., USA) that were selectively bred for high (HiS) and low (LoS) saccharin consumption (BadiaElder et al 1996;Dess and Minor 1996;Dess et al 1998) on the acquisition of IV cocaine and heroin selfadministration. Cocaine self-administration under a progressive ratio (PR) schedule was also evaluated under limited conditions.…”

Impulsivity (delay discounting) for food and cocaine in male and female rats selectively bred for high and low saccharin intake

“…Briefly, the HiS/LoS rat lines were started by pairing an avid saccharin-drinking male with several females that had average levels of saccharin consumption. In subsequent generations, HiS males with were paired with HiS females, and LoS males were paired with LoS females (Dess and Minor, 1996). By the third generation, the saccharin intake of the HiS and LoS lines diverged.…”