Ontogeny of hyperactivity and circling behavior in a transgenic insertional mutant mouse

In a previous study (Ratty et al., 1990), the discovery of a transgenic mutant mouse that displayed abnormal circling behavior was reported. Mice homozygous for the transgene display this phenotype, whereas heterozygotes are phenotypically normal. In this study, circling mutants displayed excessive lateralized circling behavior and locomotor hyperactivity by Postnatal Days (PND) 14 and 16, respectively. These abnormalities persisted unattenuated through adolescence and adulthood. Disturbances in rearing and grooming were also observed in circling mutants. Surface-righting ability in the mutants was normal, and the age of eye opening was only marginally delayed. However, body weights of the mutants were reduced compared with normal mice from PND 15 to adulthood. Possible relationships between the behaviors that are exhibited by circling mutants and previous neurochemical findings are discussed.