OPEN-FIELD DEFECATION IN RATS: RELATIONSHIPS WITH BODY WEIGHT AND BASAL DEFECATION LEVEL.

Correlations were computed between defecation and ambulation scores from the open-field test, body weight, and the basal defecation level as measured over a 5-day period in the animals' home cages for male and female hooded rats. The pattern of correlations indicates a sex difference in the ‘meaning’ of open-field defecation which appears to be a valid emotionality index only in females. In males the score correlates positively with body weight and basal defecation level. But the sex difference in the level of open-field defecation obtained probably represents a genuine sex difference in responsiveness to the test situation, since it persists even when the scores are corrected to take account of underlying basal differences in the amount of faeces available as inferred from the home-cage defecation scores. The results are discussed in terms of the validity of the defecation index and discrepancies in the literature on emotionality. [ABSTRACT FROM AUTHOR]