Brain Research, 411 (1987) 187-189 187 Elsevier BRE22260 Spontaneous alternation and habituation in Purkinje cell degeneration mutant mice Robert Lalonde, Maryse Manseau and M.I. Botez Hdtel-Dieu Hospital, Neurology Service, Section of Behavioral Neurology, Montreal, Que. (Canada) (Accepted 3 February 1987) Key words: Purkinje cell degeneration; Mutant mouse; Spontaneous alternation; Habituation; Cerebellum Purkinje cell degeneration (pcd) mutant mice were found to be as active as normal mice in a T-maze. The pcd mutants, contrary to normal mice, did not alternate spontaneously in either a 2-trial or a 4-trial test. Results are discussed in terms of a role for the cerebel- lum in behavioral inhibition and visuo-spatial organization. Purkinje cell degeneration (pcd) mutant mice lose nearly all Purkinje cells between the third and fourth postnatal weeks 17. Granule cell loss occurs after the Purkinje cell loss (beginning on the third month) 9. There is also a loss of retinal photoreceptors in pcd mutant mice, which follows a much slower course than the Purkinje cell loss 16. In spite of cerebellar damage in the pcd mutants, preliminary observations seemed to indicate that these mice are very active. Previous experimentation in two other cerebellar mutants, the nervous mouse and the lurcher mouse, both of which with Purkinje cell atrophy as well, indicated that in spite of ataxia, these mice are not less active than normal mice 14,15. Motor activity was therefore measured in pcd mu- tants in order to verify whether a massive degenera- tion in Purkinje cells results in decreased motor activ- ity. In addition, spontaneous alternation behavior was tested. In a T-maze, it is well known that normal mice or rats turn right after turning left (or vice-ver- sa) a°'a4,aS. Lesions in various brain areas impair this species-specific behavior, including the cerebel- lum 14'a5. Two tests of spontaneous alternation were performed: a 2-trial test and a 4-trial test, in order to verify the hypothesis that pcd mutant mice, contrary to normal mice, do not alternate spontaneously in a T-maze above chance levels. Ten pcd (pcd/pcd) mutant mice and 13 littermate controls (+/-) served as subjects. The mice were at least 4 weeks old at the start of the study. On arrival from Jackson Laboratory (Bar Harbor, ME), they were kept in group cages. Food and water were avail- able at all times. Exploration behavior was tested in a T-maze 15 made of transparent plastic (stem: 81.5 x 8.5 cm; arms: 30 x 8.5 cm; height: 10.2 cm). During the first 3 days, the mice were tested for spontaneous alternation in a discrete 2-trial procedure. On the first trial, the mice turned either left or right in a forced-trial procedure. About half the mice of each group turned left and the other half turned right, with the opposite arm being blocked for that trial. After entering the maze arm, they were kept in it for 60 s. On the second trial, they could either select the famil- iar arm or enter the other arm. During days 4-6, the mice were tested for motor- activity in the T-maze. The number of square cross- ings was counted in a 4-min session. The maze was separated into 13 approximately equally spaced squares by placing strips of adhesive tape under the Correspondence: R. Lalonde, H6tel-Dieu Hospital, Neurology Service, Section of Behavioral Neurology, Montreal, Que., Canada H2W 1T8. 0006-8993/87/$03.50 © 1987 Elsevier Science Publishers B .V. (Biomedical Division)