An analysis of methylphenidate induced gnawing in guinea pigs

20 compounds acting on the central nervous system and the autonomic nervous system were tested in guinea pigs for their ability to induce gnawing. Only methylphenidate induced vigorous gnawing similar to that produced by apomorphine and amphetamine. Methylphenidate differs in its mode of action from both apomorphine and amphetamine. In the guinea pig, phenylethyl configuration with OH groups at para and meta positions of the phenyl ring does not seem to be an essential criterion for inducing gnawing as suggested for the rat (Ernst, 1965). Catecholamines do not appear to play any significant role in the mediation of methylphenidate gnawing, or even in the gnawing response itself in guinea pigs, since increase in the level of dopamine and other catecholamines does not induce gnawing.Communication No. 1394 of Central Drug Research Institute, Lucknow, India.