Strain differences in response to shock in rats selectively bred for emotional elimination

It was found that the MNR strain, which learns shuttle-box CARs more quickly than the MR strain, nevertheless performed more motor responses incompatible with efficient shuttle- box crossing than the Mr. MR.

Abstract

Rats of the MNR and MR bi-directionally selected strains were given matched-impedance shocks. Shocks were escapable, inescapable, or inescapable and paired with a buzzer CS. Motor responses and skin resistance, which were recorded during each shock, differed between the strains. It was found that the MNR strain, which learns shuttle-box CARs more quickly than the MR strain, nevertheless performed more motor responses incompatible with efficient shuttle-box crossing than the MR. This paradox is discussed and it is concluded that study of behaviour other than motor response to shock is needed to clarify the determinants of avoidance behaviour in these strains.