Isoteoline is a compound of aporphine structure derived from the alkaloid glaucine. Previous studies with isoteoline have shown antagonistic activity at 5-HT(2C) serotonergic receptors. We have investigated whether isoteoline interacts with 5-HT(1B) receptors. An isolation-induced social behavioural deficit test in mice was used as a model of stimulation of these receptors. The deficit in the behaviour of isolated mice in this experimental procedure was reported to be sensitive to 5-HT(1B)-receptor stimulation, since agonists at these receptors are capable of reversing it. In our study, we used N-(3-trifluoromethylphenyl)piperazine (TFMPP) (2 mg kg(-1)) as a reference agonist at these receptor sites. TFMPP completely restored the normal behaviour of the isolated mice. Its effect was prevented by propranolol (4 mg kg(-1)), a beta-adrenergic receptor antagonist with a high affinity for 5-HT(1B) receptors, which was inactive by itself. When isoteoline was given before TFMPP, it did not prevent the effect of the latter. Given alone at doses of 0.25, 1, 4 or 8 mg kg(-1), isoteoline showed an effect of its own to normalize the behaviour of isolated mice. The effect of isoteoline (1 mg kg(-1), i.p.) was antagonized by pretreatment with propranolol, indicating that it was mediated through stimulation of 5-HT(1B) receptors. Repeated treatment with isoteoline (1 mg kg(-1), 2 x 3 days, i.p.) produced tolerance to its effect and significantly attenuated the effect of TFMPP, when animals were tested 16 h after the last injection. In conclusion, the results provided functional evidence of agonist-like activity of isoteoline at the 5-HT(1B) receptors.

Baicalin, baicalein, wogonoside and wogonin are flavone constituents of Scutellariae Radix with various beneficial biological activities. The purpose of this study was to investigate the urinary pharmacokinetics of these flavones after oral administration of Scutellariae Radix commercial powder. Ten healthy male volunteers received a dose of 5.2 g commercial powder (comparable to 9 g crude drug), respectively. The concentrations of baicalin, baicalein and wogonin in the commercial powder as well as their metabolites in urine were assayed by HPLC method. The glucuronides and sulfates of baicalein and wogonin in urine were hydrolyzed with b b-glucuronidase and sulfatase, respectively. Our results showed that the mean cumulated renal excretion of baicalein glucuronides and sulfates were 43.1؎4.5 m mmol (2.9% of dose) and 64.8؎6.3 m mmol (4.3% of dose), respectively, whereas wogonin glucuronides and sulfates were 21.6؎2.0 m mmol (5.9% of dose) and 20.7؎1.7 m mmol (5.7% of dose), respectively. The result indicated that the renal excretion of conjugated metabolites of wogonin (11.6% of dose) were higher than that of baicalein (7.2% of dose). The baicalein sulfates was predominant than the corresponding glucuronides, whereas wogonin sulfates was comparable to the corresponding glucuronides.

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