Sex differences in catalepsy: evidence for hormone-dependent postural mechanisms in haloperidol-treated rats

Catalepsy, a symptom of Parkinson's disease and related disorders can be pr oduced in rats and other laboratory animals by the blockade of nigrostriata l dopamine using dopaminergic antagonists such as haloperidol. When haloper idol-induced cataleptic rats are placed facing downward on an inclined plan e, they will brace against the resulting downward force by pushing backward s, and if they lose postural stability, or their position on the inclined p lane, they will jump forward. Females, however, jump from the inclined plan e at a significantly lower angle than do males. Frame-by-frame analysis of the jumping sequences revealed that females and males use a different combi nation of postural adjustments to maintain their position on the inclined p lane prior to jumping. Furthermore, gonadal hormone manipulations at birth and in adulthood reveal that these sex differences in postural adjustments are dependent on the organizational effects of gonadal hormones in the peri natal period. These results provide evidence for sex differences in postura l support mechanisms and suggest that the sex of subjects, or their hormona l state, must be considered when studying the behavioral aspects of neurolo gical disorders such as Parkinson's disease which include a postural compon ent. (C) 2000 Elsevier Science B.V. All rights reserved.