Induced grooming transitions and open field behaviour differ in high- and low-yawning sublines of Sprague-Dawley rats

摘要

Water immersion-induced grooming sequences and open field behaviour were studied in two sublines of Sprague-Dawley rats, Rattus norvegicus, selectively bred for high- (HY) and low-yawning (LY) frequency. HY rats were more active than LY rats in the open field: ambulation, rearings and wall-leanings were significantly higher in the former than in the 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 that both groups groom according to a hierarchical organization, with transitions 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 distinct 'syntaxes' of grooming elements. Altogether these results indicate that along with a high or low frequency of yawning, there are other associated types of behaviour that separate both groups of rats. The structure of grooming between HY and LY rats indicates a strain-specific functional and neurophysiological difference. Yawning, grooming and emotional reactivity appear to be associated with arousal variations.