[On the central inhibition action of tetrahydroberberine without relevance to GABA receptors].

Using an earthworm (Eisenia foetida) dorsal muscle preparation, it was shown that tetrahydroberberine (THB, 10(-7)-10(-4) mol/L) did not affect both GABA and ACh receptors. DA receptor antagonist haloperidol (HAL) also exerted no effect. Owing to the blocking action of isonicotinyl hydrazine (INH) and thiosemicarbazide (TSC) on biosynthesis of GABA, and of picrotoxin (PT) and bicuculline (Bic) on the GABA-BZ receptor complex mediated transmission, all these agents could induce convulsion in mice. This action could be antagonized by amino- oxyacetic acid (AOAA) and benzodiazepine (BZ), but not by DA receptor antagonists THB and HAL. All the above observations indicate that the GABA inhibition is not involved in the central action of THB.