Peripheral autonomic mechanisms and Pavlovian conditioning in the rabbit (Oryctolagus cuniculus)

The present experiments examined the effects of peripheral administration of atropine methyl nitrate and 6-hydroxydopamine hydrobromide on differential classical conditioning or eye-blink (EB) and heart rate (HR) responses in the rabbit. Atropine decreased HR conditioned response (CR) magnitude and increased baseline HR, although the latter declined somewhat over the first few sessions of the experiment. As baseline HR declined, EB CRs increased in animals treated with atropine. However, the acquisition of the EB response was impaired in these subjects compared with animals treated with saline. The administration of 6-hydroxydopamine produced an impairment of the HR response early and late during acquisition but had no effect on EB conditioning. Control experiments suggested that the impairments produced by methyl atropine were not due to general somatomotor deficits or to a differential sensitivity to the electric shock unconditioned stimulus. The conditioning data are consistent with the Laceys' peripheral afferent feedback hypothesis of autonomic-somatic relations.