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 high-saccharin (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.