A simple method for the study of yawning in man induced by the dopamine receptor agonist, apomorphine

Apomorphine (Apo), a dopamine (DA) receptor agonist, induces yawning by stimulating central DA autoreceptors. Few data are available on Apo-induced yawning in man. A simple method for recording and measuring Apo-induced yawning by measuring the displacement of the lower jaw using a pair of linearlized magnetometers with one sensor attached to the forehead just below the hairline and the other under the chin is described. The output of the magnetometers is fed into a DC amplifier and displayed on a strip chart recorder. Complete concordance between evaluators reading the tracings and between observed yawning and recorded yawns was found. Measuring Apo-induced yawning may provide a simple approach to evaluating DA autoreceptor function in normal subjects and in patients with psychiatric and neurological disorders. Preliminary data show that Apo-induced yawning is more marked in women than in men. This is in contrast to spontaneous and drug-induced yawning in animals which is predominantly a male phenomenon. Sleep appears to inhibit Apo-induced yawning.