Hippocampal injections of KCl and shock-induced bradycardia in the rat

Rats given hippocampal injections of 25% solution of KCl 24 h after tone-shock pairings do not show bradycardia when presented subsequently with the tone alone. Animals given the same training but with saline injections do show cardiac deceleration. KCl injections themselves have no effect on heart-rate response to a tone. The results are discussed in terms of previous research indicating that KCl injections also produce a retention deficit in a CER paradigm, the suggestion being that the deficit in the CER paradigm is mediated by a failure to retain fear conditioning.