Vasopressin deficiency and blood glucose interactions on passive avoidance behavior

The performance of a passive avoidance task (measured for two trials based upon number of complete step-downs and latency to respond) and blood glucose levels were examined in five groups of animals. The groups included vasopressin-deficient (DI) and vasopressin-containing (LE) rats under ad lib (AL) and food-restricted (FR) conditions, as well as DI-FR animals provided with access to an 8% sucrose solution (SUC). In the AL condition, no significant differences were found between DI and LE animals in either step-down occurrences or blood glucose levels. However, the DI animals were significantly slower in latency to respond in trial 1. With FR, the LE animals resembled the LE-AL animals in both passive avoidance behavior and blood glucose levels. The DI-FR animals that were not provided with SUC showed an impairment in passive avoidance behavior and low blood glucose levels, whereas DI-FR animals provided with SUC showed an amelioration of passive avoidance deficiencies and had blood glucose levels comparable to AL animals and LE-FR animals. On trial 2, a significant negative correlation was found between number of step-down occurrences and blood glucose levels, and a significant positive correlation was found between latency to respond and blood glucose levels. The experiment demonstrates that: 1) because DI rats have a different responsiveness in novel situations, caution must be exercised in using response latency as a measure of passive avoidance performance in the AL condition; 2) AL and FR conditions produce different responses in DI, but not LE, animals; 3) deficiencies in passive avoidance behavior in DI-FR rats can be ameliorated by the consumption of exogenous carbohydrate; and 4) there is a significant correlation between blood glucose levels and passive avoidance behavior.