Intraseptal scopolamine has differential effects on Pavlovian eye blink and heart rate conditioning.

Abstract

The effects of intraseptal scopolamine hydrobromide injections on Pavlovian (classical) conditioning were evaluated, with tones used as the conditioned stimulus (CS) and a periorbital electric shock train as the unconditioned stimulus (UCS). Eye blink (EB) and heart rate (HR) conditioned responses were concomitantly recorded. Although injections of scopolamine into the medial septum impaired the acquisition of the Pavlovian conditioned eyelid reflex, these injections enhanced the magnitude of accompanying Pavlovian conditioned HR decelerations. However, scopolamine applied to the lateral septal area had no effect on EB conditioning, relative to the vehicle, but, like medial injections, enhanced the magnitude of the accompanying HR decelerations. These results are compatible with those of previous investigations: Medial septal dysfunction impairs somatomotor conditioning but leaves autonomic conditioning intact, and septal dysfunction produces a parasympathetic bias of the cardiovascular system.