INHERITANCE OF PREDISPOSITION TO CATALEPSY IN MICE

''Pinch-induced'' catalepsy (excessive freezing) was studied in mice of nine inbred strains. The CBA/Icg strain had the highest predisposition to catalepsy, with 56% males and 73% females exhibiting 120-s immobility after four tests. A Mendelian analysis of predisposition to catalepsy was performed on CBA/Icg and AKR/J mice contrasting in this trait. Reciprocal F1 hybrids did not display freezing after 10 tests. The number of cataleptic and noncataleptic animals among the F2's and in the families of the CBA x F2 backcrosses agreed with the hypothesis that the pronounced predisposition to catalepsy in the CBA/Icg mice was determined by a single autosomal locus in homozygous recessive condition.