[Behavioral pharmacology of berberine-type alkaloids. (2) Central depressant effects of tetrahydroberberine (THB) and related compounds].

The behavioral effects of tetrahydroberberine (THB), tetrahydrocoptisine (THC), tetrahydropalmatine (THP) and tetrahydrojateorrhizine (THJ) were compared with those of chlorpromazine (CPZ) and benzodiazepines in mice and rats. Effects of THB were also determined by electroencephalography (EEG) in rabbits. THB was found to pharmacologically exert various actions similar to those of CPZ which is a major tranquilizer, however, the actions of THB were weaker than those of CPZ. Although THB alone did not induce catalepsy, it enhanced the cataleptogenic action of CPZ. At a dose over the effective levels, THB did not lower normal body temperature or induce muscle relaxation and loss of righting reflex. EEG activities in the frontal cortex areas were markedly affected by THB, e.g., fast waves in spontaneous EEG were converted to slow waves. THB and CPZ in a similar manner elicited a sustaining increase in hippocampal afterdischarge, but the action of THB was weaker than that of CPZ. The acute toxicity of THB was lower than that of CPZ and benzodiazepines and the depressant activity of THB almost equalled that of THC and THP, whereas the activity of 1-THB was 1.5 times as great as that of THB. These data indicate that THB, THC and THP may be a new type of tranquilizer.