Abstract
In Experiment I, male and female rats from the spontaneously hypertensive (SHR) and WistarβKyoto (WKYN) normotensive strains were given 1 session of 2βway shuttlebox avoidance training at 25β26, 35β36, or 45β46 days of age. The avoidance training was preceded by a pretest which consisted of 10 presentations of the compound conditioned stimulus alone in order to assess any differential tendency of the 2 strains to respond to the presentation of novel stimuli. The WKYN rats made a significantly higher number of pretest avoidance responses and achieved a higher level of avoidance performance than SHR rats. In addition, during the pretest, WKYN rats were more active and had a shorter 1st trial latency. In Experiment II, the pretest phase was replicated with a manipulation of the intensity of the auditory cue. Although the WKYN rats had a higher rate of pretest avoidance than SHR rats, the rate of pretest avoidances increased with intensity in both strains. The WKYN rats had a shorter 1st trial latency and a shorter median latency for the 10 trials and were more active than SHR rats during the pretest. These results relate to ageβindependent behavioral characteristics of these strains and the question of reactivity to environmental stimulation.