DOES RESERPINE INDUCE PARKINSONIAN RIGIDITY

The aim of the study was to find out whether the reserpine-induced rigidity is similar to that seen in parkinsonism. Simultaneous measurements of the muscle resistance of the hind foot to passive bending and stretching in the ankle joint, as well as of the electromyographic (EMG) activity of the gastrocnemius and tibialis anterior muscles of rats were carried out. Reserpine was injected in a dose of 10 mg/kg alone or with alpha-methyl-p-tyrosine (250 mg/kg) 1, 4 and 27.5 h before the measurements. Reserpine increased the muscle resistance of the rat's hind leg to passive movements. That effect was the strongest at 1-2 h after the injections, and diminished markedly afterwards. The rigidity was accompanied with an increase in the resting, as well as in the stretch-induced short- and long-latency EMG activity in the gastrocnemius muscle. However, the intensity of the latter symptom did not change for a long period of time, which seems to correlate with the striatal dopamine depletion. The results suggest that the reserpine-increased EMG activity is a good model of parkinsonian rigidity.