Application of models of spasticity and spastic paralysis

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Intercollicular decerebrate rigidity (so-called <gamma> -rigidity) and anaemic decerebrate rigidity ( <alpha> -rigidity) have been used in pharmacological and physiological studies in cats. Because rats are usually used in behavioural and neurochemical studies for their ease of handling, however, we have produced both types of rigidity using rats in the evalustion of centrally acting muscle relaxants (Fukuda et al., 1974; Togari et al., 1978).The rate of success of intercollicular decerebrate rigidity has not been high probably due to compression of the brain by bleeding or the difficulty involved in precisely controlling the spatula. In order to avoid such problems, radio frequency (RF) lesion of the midbrain was produced in attempts to obtain a good preparation of rigidity and to establish an easy method of decerebration in rats.The effects of chlorpromazine (CPZ), a frug which preferentially depresses intercollicular decerebrate rigidity, and mephenesin, a centrally acting muscle relaxant, were evaluated on the RF decerebrate rigidity.1. Bilateral RF lesions of the midbrain were produced in an attempt to establish a non-bleeding method of producing decerebrate rigidity in rats.2. Marked extensor rigidity occurred with a high reproducibillity in hindlimbs without the appearance of voluntary movement. Stretch reflex tension induced by repetitive dorsiflexion of the hindfeet was employed as a measure of the intensity of rigidity.3. CPZ-HCL (0.1-1 mg/kg, i.v.) and mephenesin (10-50 mg/kg, i.v.) which depress intercollicular decerebrate rigidity, reduced the RF decerebrate rigidity.4. These results suggest that RF decerebrate rigidity can be used instead of intercollicular transection rigidity in the pharmacological and physiological studies.