Vagotomy facilitates extinction of conditioned taste aversions in rats

• Published in: Journal of comparative & physiological psychology Vol. 95; no. 1; p. 114
• Main Authors: Kiefer, S W, Rusiniak, K W, Garcia, J, Coil, J D
• Format: Journal Article
• Language: English
• Published: United States 01.02.1981
• Subjects: Afferent Pathways - physiology; Animals; Avoidance Learning - physiology; Brain Stem - physiology; Conditioning, Classical - physiology; Extinction, Psychological - physiology; Male; Rats; Taste - physiology; Vagotomy, Proximal Gastric; Vagus Nerve - physiology
• ISSN: 0021-9940
• DOI: 10.1037/h0077751

Results from three experiments indicate that severing the subdiaphragmatic vagus in rats increased the rate of extinction of learned taste aversions. In Experiment 1, although vagotomized rats acquired a saccharin aversion equivalent to that of controls when the illness-inducing agent was the blood-borne toxin apomorphine, vagotomized rats tended to consume more saccharin than controls during repeated extinction tests. In Experiment 2, vagotomy disrupted retention and increased extinction of a preoperatively acquired saccharin aversion. Disruptions were found when the taste aversion was induced by copper sulfate, a local gastric irritant (Experiment 2A), or apomorphine, a systemic toxin (Experiment 2B); in each experiment vagotomized rats consumed more saccharin than controls on the first retention test and extinguished the prior to surgery. Experiment 3 demonstrated that vagotomy did not affect retention or extinction of a shock-induced conditioned emotional response (lick to suppression) to noise. It is concluded that integrity of the vagus is not necessary for acquisition of a learned taste aversion when a blood-borne toxin is used as the ill-inducing agent. However, the vagus apparently mediates an integral portion of the conditioned response following taste-illness acquisition regardless of whether the illness agent is a local gastric irritant or a systemic toxin.