COMPARISON OF THE ELECTROENCEPHALOGRAPHIC AND MOTOR EFFECTS OF ORPHENADRINE, AN ANTIPARKINSON AGENT

Abstract

Orphenadrine has been reported to improve effectively a variety of skeletal muscle spasms (1-5) and various disorders of parkinsonism (6-9). Orphenadrine is known to be one of anticholinergic agents with weak antihistamine activity (9). The anticholinergic and antihistamine mechanisms seem to be somewhat essential for the antiparkinson drugs (10, 11). The blocking effects of the anticholinergic antiparkinson agents on the reticular ascending function (12) as well as the suppressing effects on the tremor induced either by destructive lesions in the midbrain tegmentum (12) and the reticular formation (14) or by electrical stimulation of these structures (15, 16) indicate that the cholinergic mechanism is involved somewhere in the polysynaptic chains of the ascending and descending pathways from the midbrain. These evidences indicate that the suppression of the arousal response in the cortical EEG is predictive for the prevention of the tremor manifestation in the parkinson patients. Such an effect has been utilized for the evaluation of the antiparkinson agents (10, 12). In the present experiments the effects of various agents including orphenadrine were observed on the arousal responses of the cortical EEG and on the motor responses such as the head turning and neck tremor caused by electrical stimulation of the midbrain tegmentum. However, the uniform and parallel depression of both parameters was not always obtained, varying considerably in effect according to the administered doses and also to the time-length after the administration. The antiparkinson characteristics of orphenadrine were discussed, based on the evidences obtained.