Peripheral 6-hydroxydopamine administration in the rabbit (Oryctolagus cuniculus): effects on Pavlovian conditioning.

The present experiment studied the effects of 6-hydroxydopamine (6-OHDA) administration and adrenal enucleation on differential classical conditioning of somatic and cardiovascular changes in the rabbit. Heart rate and blood pressure conditioned responses (CRs) were relatively large decreases in rate and slight depressor responses, respectively, which were both attenuated by 6-OHDA administration and adrenal demedullation. Frequency of eye-blink response to the reinforced conditioned stimulus was diminished by sympathetic interference during the middle sessions of conditioning, thus producing a decrement in eye-blink discrimination. Electromyographic CRs, on the other hand, were not affected by peripheral catecholamine reduction. These results are discussed in terms of the role of afferent autonomic feedback in influencing the acquisition of somatomotor behaviors.