Postsynaptic dopamine agonist properties of TL-99 are revealed by yohimbine co-treatment.

The claim that TL-99 (6,7-dihydroxy-2-dimethylaminotetralin hydrobromide) is a selective dopamine autoreceptor agonist relies partly upon indirect behavioral evidence, particularly the absence of stereotyped behavior in treated rats. The possibility was examined that concurrent alpha 2-adrenoceptor agonist properties of TL-99 could have masked postsynaptic dopamine agonist activity. Co-administration of yohimbine or piperoxan with a high dose of TL-99 (30 mg/kg) dramatically increased motor activity in reserpinized rats, whereas each drug by itself had no effect.

Progressive changes in the acute dyskinetic syndrome as a function of repeated elicitation in squirrel monkeys.

Various neuroleptic-induced motor disorders that appear in primates previously treated with neuroleptics are collectively designated the acute dyskinetic syndrome. The relative incidence of these motor disorders was examined as the syndrome was repeatedly elicited by haloperidol and other dopamine antagonists in individual monkeys. After several weekly or biweekly treatments with haloperidol (1.

Acute dyskinesias in monkeys elicited by halopemide, mezilamine and the "antidyskinetic" drugs, oxiperomide and tiapride.

Oxiperomide and tiapride are dopamine receptor antagonists claimed to have "antidyskinetic" properties in animal models and the clinic. Halopemide and mezilamine are other dopamine antagonists predicted to lack extrapyramidal side effects in man on the basis of animal studies. Acute dyskinesias, a neuroleptic-induced acute extrapyramidal syndrome, were elicited in squirrel monkeys by oxiperomide (1 mg/kg), tiapride (30 mg/kg), and halopemide (10 mg/kg).