The mutants exhibit a form of paroxysmal akinesia when suddenly disturbed in their cage. They freeze in abnormal positions for 20-30 seconds, i.e. may be crouched with head down, or lie on their side with one limb positioned stiffly at their side. When picked up by their tail, the hind limbs extend stiffly forward, the front limbs paddle swiftly. The animals recover quickly and then move about normally.
In two of three mutant EEGs, short, low amplitude ( 4 Hz spike-wave complexes; 0.5 - 1.5s, 10 - 15 uV), were observed while the animal was awake but immobile. The frequency was about 10 times per hour, although low-amplitude single or double spikes were seen at greater frequency. The spike-wave complexes did not coincide with, although sometimes followed, episodes of intermittent movement abnormality. In one animal tested, the single spikes and spike-wave complexes were eliminated after administration of 150 mg/kg ethosuximide, i.p., suggesting that these events may represent absence seizures.
Standard pathology work-up on three mutants (57, 75 and 150 days of age) revealed thickening of the petrous temporal bone in one animal, however, serial sections of the second animal's ear showed no abnormalities. There appeared to be some gaps in the purkinje cell layer of the parafloccular lobes of the cerebellum, but the rest of the cerebellum looked normal.
