Effects of KB-2796 on plasma extravasation following antidromic trigeminal stimulation in the rat

We investigated the effects of KB-2796 (1-[bis(4-fluorophenyl)methyl]-4-(2,3,4-trimethoxybenzyl)piperazine dihydrochloride), a novel calcium channel blocker, on neurogenic inflammation caused by electrical stimulation in the trigeminal ganglion and on cutaneous reactions induced by inflammatory mediators in rats, by measuring plasma extravasation. Neurogenic inflammation was inhibited by pretreatment with capsaicin (25 mg/kg, s.c.) but not indomethacin (10 mg/kg, i.p.), while phosphoramidon (2.5 mg/kg, i.v.) augmented it. KB-2796 (0.1-1 mg/kg, i.v.) significantly inhibited neurogenic inflammation in a dose dependent manner, without affecting histamine-, bradykinin- or substance P-induced cutaneous reactions. Dimetotiazine (0.3 and 1 mg/kg, i.v.), flunarizine (1 mg/kg, i.v.), mepyramine (1 mg/kg, i.v.) and sumatriptan (1 mg/kg, i.v.) significantly inhibited neurogenic inflammation. However, these compounds also showed complete or partial inhibition of histamine-, bradykinin- or substance P-induced reactions. Nifedipine (0.1 mg/kg, i.v.) did not show marked effects on neurogenic inflammation and cutaneous reactions. The present experiments indicate that neurogenic inflammation is presumably mediated not only by neuropeptides released from trigeminal nerve endings but also by secondarily released histamine, and that KB-2796 like sumatriptan may inhibit neurogenic inflammation caused by trigeminal nerve stimulation probably through inhibition of neuropeptide release but its inhibition may be distinct from the calcium blocking action of the 1,4-dihydropyridine type.