The electrocardiogram of Roman high- and low-avoidance rats under pentobarbitol sodium anesthesia

Strain-sex differences have previously been observed between RHA and RLA male (m) and female (f) rats in the sensitivity to pentobarbital sodium. This present study further investigated the effect of these factors on the electrocardiogram. The heart rate was depressed at all levels of anesthesia, with the maximum effect at 40 min post-infection. Although the heart rate subsequently increased, the P-R and Q-T intervals lengthened progressively throughout the 2 h, accompanied by steady increases in the T-wave amplitude. Some strain-sex differences were seen in the Q-T interval (RHAm, RLAf greater than RLAm), the T wave amplitude (RHAmf greater than RLAmf) and the S-wave amplitude (RHAmf greater than RLAmf, RHLAf greater than RHLAm).