title: Alpha2 adrenoceptors modulate histamine release from sympathetic nerves in the guinea pig vas deferens.
abstract: In our previous studies, we have identified that histamine (HA) is co-released with noradrenaline (NA) from the sympathetic nerve terminals and acts as a novel sympathetic neurotransmitter. However, the modulation of sympathetic HA release by sympathetic prejunctional receptors is still unknown. Therefore, in this study, we explored the modulation effect of alpha(2) adrenoceptors on sympathetic HA release and the interaction of alpha(2) adrenoceptors with HA H(3) receptors in vas deferens isolated from guinea pig. The selective alpha(2) adrenoceptor agonist brimonidine decreased the HA overflow in a concentration-dependent manner and abolished the contractile responses mediated by sympathetic HA release. Yohimbine competitively blocked the effect of brimonidine on HA release. Similarly, the HA H(3) receptor agonist R-(alpha)-methylhistamine also decreased HA release, and thioperamide blocked the effect of R-(alpha)-methylhistamine. When used singly, both yohimbine and thioperamide facilitated HA release. In addition, the inhibitory effect of brimonidine on HA release was stronger in the presence of thioperamide, while it was reduced when HA H(3) receptors were activated by R-(alpha)-methylhistamine. Our findings indicate for the first time that sympathetic HA release is negatively modulated both by prejunctional alpha(2) receptors and HA H(3) receptors and that these two prejunctional receptors interact with each other in modulating sympathetic HA release.
authors.affiliation: Department of Pharmacology, School of Pharmacy, The Fourth Military Medical University, Xi' an 710032, PR China.
authors.forename: Gonghao
authors.initials: G
authors.lastname: He
authors.forename: Xue
authors.initials: X
authors.lastname: Ma
authors.forename: Jun
authors.initials: J
authors.lastname: Lu
authors.forename: Jingru
authors.initials: J
authors.lastname: Meng
authors.forename: Yingying
authors.initials: Y
authors.lastname: Chen
authors.forename: Min
authors.initials: M
authors.lastname: Jia
authors.forename: Xiaoxing
authors.initials: X
authors.lastname: Luo
mesh_terms: D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists / Q000008:administration & dosage / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D000068438:Brimonidine Tartrate; D002744:Chlorpheniramine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D017442:Histamine Agonists / Q000494:pharmacology; D006634:Histamine H1 Antagonists / Q000494:pharmacology; D054828:Histamine H3 Antagonists / Q000494:pharmacology; D006636:Histamine Release; D066298:In Vitro Techniques; D008297:Male; D008761:Methylhistamines / Q000494:pharmacology; D010525:Peripheral Nerves / Q000187:drug effects / Q000502:physiology*; D010880:Piperidines / Q000494:pharmacology; D011810:Quinoxalines / Q000008:administration & dosage / Q000494:pharmacology; D043683:Receptors, Adenosine A2 / Q000378:metabolism*; D018100:Receptors, Histamine H3 / Q000378:metabolism; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000502:physiology*; D014649:Vas Deferens / Q000187:drug effects / Q000294:innervation / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
chemical_list: D058908:Adenosine A2 Receptor Agonists; D058917:Adenosine A2 Receptor Antagonists; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D017442:Histamine Agonists; D006634:Histamine H1 Antagonists; D054828:Histamine H3 Antagonists; D008761:Methylhistamines; D010880:Piperidines; D011810:Quinoxalines; D043683:Receptors, Adenosine A2; D018100:Receptors, Histamine H3; D015016:Yohimbine; D002744:Chlorpheniramine; D000068438:Brimonidine Tartrate; C069357:alpha-methylhistamine; C052075:thioperamide