[A morphological study on the brain in wriggle mouse Sagami, a new neurological mutant with dystonic disorders, with special reference to the abnormality of the cerebellum].

The 'Wriggle Mouse Sagami (WMS)' is a new neurological mutation that was discovered in an inbred strain of BALB/c mice at the Ohmura Institute for Laboratory Animals (Address: Zama 228, Kanagawa, Japan) in 1984. The affected characteristics are transmitted by an autosomal recessive gene (wri). The clinical symptoms are characterized by dystonic involuntary movements, such as fine tremors of the forelimbs, hypertonic musculature of the extremities, difficulty in maintaining an upright posture, writhing of the trunk, wriggling of the neck up-and-down and from side to side without any coordination between the movements of the limbs and trunk, and inability to walk a staigho that begin at 10 days to 2 weeks after birth and are progressive until 12 weeks of age. Here a morphological study on the brain of the WMS with special reference to the cerebellum was intended. The results were as follows: (1) In spite of these severe clinical symptoms, no marked abnormalities were observed in the cyto- and myeloarchitecture of the central nervous system, although the size of the whole brain was somewhat reduced and the molecular layer of the cerebellum was relatively hypotrophic compared with the granule cell layer. (2) The motor tracts investigated were normally detected by the retrograde HRP-labeling method. (3) Slight abnormality of the dendritic trees and spines, and remarkable axonal swellings of the Purkinje cells were demonstrated by a sensitive immunohistochemical method for inositol 1,4,5-trisphophate receptor protein (P400 protein). These changes were also evaluated by the Golgi method. (4) In electron microscopy of the molecular layer of the WMS cerebellum, parallel fibers seemed to be reduced and shrunken, and their synaptic contacts on the dendritic spines of the Purkinje cells were clearly reduced even at 17 days after birth. (5) Consequently, the Purkinje cells were possibly affected by failure of accurate connection with input fibers or by synaptic dysfunction, which might occur over the entire central nervous system.