Effects of atropine sulphate on hippocampal rhythmic slow activity during a conditioned locomotor response in the cat.

In cats atropine sulphate injected intraperitoneally in doses of 1.0 and 2.0 mg/kg abolished the hippocampal rhythmic slow activity (RSA) accompanying the performance of instrumental active avoidance response in a shuttle box. The action of atropine consisted in a gradual elimination of RSA, the RSA of slower frequency occurring during latency (the period of attentive immobility between the CS onset and the beginning of the conditioned locomotor response) and during the poststimulus period disappeared first, and that of a higher frequency, accompanying the initiation of the conditioned locomotor response and barrier crossing disappeared last. The speed of this process was dose dependent. The data show that the whole spectrum of RSA in the cat is atropine sensitive, but the level of this sensitivity depends on the RSA frequency.