Catatonic behaviour in the Norway rat.

Abstract

Different forms of catatonic behaviour occurring spontaneously as fright reactions in wild and laboratory Norway rat are described. In wild rats, the catatonic reaction appears in form of stupour. The frequency of this phenomenon in the 5th generation of out-bred vivarium population of wild rats is 20%, the stupour being represented by a rearing (10%) or hanging (10%) form. The threshold of this reaction is especially low in females. Predisposition to the stupour is hereditary; the mode of inheritance of this feature seems to be complex. In laboratory albino strains of rats, such akinetic form of catatonic reaction is rare (no more than 1%), but hyperkinetic phenomena in form of pendulum movements are common. These pendulum movements show a positive genotypical correlation with the predisposition to audiogenic seizures and a negative genotypical correlation with the vegetative component of emotionality. No influence of sex on the expression of pendulum movements was found. A hybridological analysis demonstrated that the predisposition to pendulum movements is linked to the inhibition of eumelanine synthesis in cc or pp homozygotes. In AUG/WAG or AUG/SD hybrids with normal eumelanine synthesis there are neither pendulum movements nor the stupour like that in wild rats; however, about 30% of them show an expressed akinetic reaction in form of freezing when placed into a strange environment. The relation of catatonic reactions to normal and pathological behaviour, and the possibility of using catatonic strains of rats as ethological models of schizophrenia are discussed.