The acute and chronic effect of 5-methoxytryptamine on selected members of a primate social colony.

The acute and chronic effect of 5-methoxytryptamine (5-MeOT), a structural analogue of known tryptamine hallucinogens and a substance found in mammalian brain, on nonhuman primate behavior was studied in a social colony of four Stumptail macaques. In the first study, dose-dependent behavioral changes induced by 5-MeOT were determined with the administration of seven acute doses to each animal. At higher doses, 10-20 mg/kg, 5-MeOT induced two abnormal or "emergent" behaviors, body shakes and limb jerks. 5-MeOT also induced a dose-dependent reduction in normal social and solitary behavior of treated animals suggesting that this drug has sedative properties. The second study examined the effect of once daily administration of 5-MeOT, 10 mg/kg, for 5 days. During this time, tolerance developed to both 5-MeOT-induced body shakes and limb jerks, but failed to develop to the reduction in social and solitary behaviors. Since body shakes and limb jerks are behaviors characteristically induced in this species by hallucinogens, these results suggest that 5-MeOT may possess hallucinogenic properties. However, this effect may be weak and may only occur after large doses since large doses of 5-MeOT were required to induce a relatively small number of body shakes and limb jerks in monkeys when compared to potent hallucinogens such as LSD and 5-MeODMT.

Bicaudate index in computerized tomography of Huntington disease and cerebral atrophy.

Ventricular sizes on computerized tomographic (CT) scans were compared in seven patients with Huntington disease, 20 patients with cerebral atrophy, and 20 normal controls. The bicaudate index--the ratio of the width of both lateral ventricles at the level of the heads of the caudate nuclei to the distance between the outer tables of the skull at the same level--significantly discriminated among the three groups. The bicaudate indices were: Huntington disease 0.209 +/- 0.007, cerebral atrophy 0.121 +/- 0.006, and controls 0.092 +/- 0.003.