Spasmodic head movements produced by destruction of unilateral ventromedial tegmentum in cats.

In cats, unilateral electrolytic destruction in the dorsomedial parts of the ventral tegmental area (VTA) (Tsai) led to the appearance of torticollic rotatory head postures associated with a marked drop of the corresponding caudate serotonin. Results obtained from fluorescence histochemistry and brain dialysis also revealed that decrease in serotonin shared the leading role. However, since a chemical lesion produced by neurotoxic agents failed to induce such abnormal postures, concomitant interruption of nonaminergic fibers at VMT might also be the essential factor. Among them the interstitial nucleus (Cajal) and its descending tract were the most suspicious.