Postural asymmetry and lateralized rotation in normal rats administered apomorphine

The study examines the hypothesis that the direction of circling exhibited by normal rats administered apomorphine reflects a drug-induced bias to use one specific hindleg for stepping and the other one for postural support. Results indicate that a majority of rats injected with this dopamine receptor agonist do show an asymmetry in the usage of the hindlegs (postural bias). However, the side of more frequent steppings does not predict the direction of circling. Moreover, postural bias may exist without lateralized circling. It is suggested that lateralized circling and postural asymmetry are two of several biases induced by apomorphine that may coexist in individual rats.