INDUCED GROOMING TRANSITIONS AND OPEN-FIELD BEHAVIOR DIFFER IN HIGH-YAWNING AND LOW-YAWNING SUBLINES OF SPRAGUE-DAWLEY RATS

Water immersion-induced grooming sequences and open field behaviour we re studied in two sublines of Sprague-Dawley rats, Rattus norvegicus, selectively bred for high- (HY) and low-yawning (LY) frequency. HY rat s were more active than LY rats in the open field: ambulation, rearing s and wall-leanings were significantly higher in the former than in th e latter group, indicating that LY rats are more emotionally reactive. Sequential analysis showed that HY rats exhibit more occurrences of a well-organized caudal grooming, while LY rats engage more frequently in well-organized facial grooming. Correspondence analysis revealed th at both groups groom according to a hierarchical organization, with tr ansitions between grooming elements depending on anatomical proximity. Clustering of grooming elements is related to a temporal recruitment and a reciprocal transition between them. Both groups, however, show d istinct 'syntaxes' of grooming elements. Altogether these results indi cate that along with a high or low frequency of yawning, there are oth er associated types of behaviour that separate both groups of rats. Th e structure of grooming between HY and LY rats indicates a strain-spec ific functional and neurophysiological difference. Yawning, grooming a nd emotional reactivity appear to be associated with arousal variation s. (C) 1995 The Association for the Study of Animal Behaviour