title: UK-14,304, R(-)-alpha-methyl-histamine and SMS 201-995 block plasma protein leakage within dura mater by prejunctional mechanisms.
abstract: Intravenous administration of an alpha-adrenoceptor agonist, UK-14,304, a histamine H3 receptor agonist, R(-)-alpha-methyl-histamine (alpha-MeHA) or SMS 201-995 (a synthetic octapeptide analogue of somatostatin), blocked plasma protein (125I-albumin) extravasation within rat and/or guinea pig dura mater following unilateral electrical trigeminal ganglion stimulation or capsaicin administration. The extravasation caused by the administration of the neuropeptide mediator, substance P, was not inhibited by any of the three compounds. Blockade by UK-14,304 was completely antagonized by pretreatment with the highly selective alpha 2-antagonist, idazoxan, as was alpha-MeHA by pretreatment with the highly selective histamine H3 antagonist, thioperamide. Taken together, the results are consistent with blockade by prejunctional alpha 2, histamine H3 and probably somatostatin receptors which may be coupled to inhibition of neuropeptide release. Because 5-HT1-like agonists, which are useful for treating migraine and related headaches, share similar inhibitory properties in this in vivo model, the significance of prejunctional alpha 2, histamine H3 and somatostatin receptors to treatment of vascular headaches is suggested.
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000818:Animals; D000068438:Brimonidine Tartrate; D002199:Capillary Permeability / Q000187:drug effects*; D002211:Capsaicin / Q000494:pharmacology; D004388:Dura Mater / Q000098:blood supply* / Q000187:drug effects; D004558:Electric Stimulation; D006168:Guinea Pigs; D017442:Histamine Agonists / Q000494:pharmacology*; D007275:Injections, Intravenous; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology*; D015282:Octreotide / Q000494:pharmacology*; D011810:Quinoxalines / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011968:Receptors, Histamine / Q000187:drug effects*; D018100:Receptors, Histamine H3; D017481:Receptors, Somatostatin / Q000187:drug effects; D013373:Substance P / Q000494:pharmacology
chemical_list: D000316:Adrenergic alpha-Agonists; D017442:Histamine Agonists; D008761:Methylhistamines; D011810:Quinoxalines; D011968:Receptors, Histamine; D018100:Receptors, Histamine H3; D017481:Receptors, Somatostatin; D013373:Substance P; D000068438:Brimonidine Tartrate; C069357:alpha-methylhistamine; D015282:Octreotide; D002211:Capsaicin