Classically conditioned heart rate and respiratory-motor activity in newborn and neonatal pygmy goats

Classical discrimination conditioning of heart rate (HR) and respiratory-motor (RM) activity was examined in 16 newborn (average age = 1 day) and 8 neonatal (average age = 2 weeks) pygmy goats over 4 days of conditioning involving an electric shock US and auditory CSs. On the 4th day, one-half of the animals in each group received a low to moderate dose of ethanol to test the resistance of the CRs to drug effects. Discriminated conditioning of RM activity but not HR occurred in the newborn group, indicating an absence of close coupling between skeletal-motor activity and HR at this early age. While the newborn group failed to show recognizable HR reactions to the CSs during the 4 days of testing, it did show a long-latency brady-cardia UR beginning at 2 days of age that may have been secondary to baroreceptor reflex actions. The neonatal group displayed conditioning of both HR and RM activity. The similar latencies of the two types of CRs during the CS suggested that they may have been related to each other. However, the fact that the RM CR developed a day before the HR CR, combined with the observation that ethanol modified the HR CR but not the RM CR, supports the view that there was considerable independence between the two types of CRs.