title: Characteristics of the responses of isolated and perfused canine splenic arteries to vasoactive substances and to periarterially electrical stimulation.
abstract: Pharmacological characteristics of the canine isolated splenic artery were investigated by the cannula insertion method for observing vascular responses to vasoactive agents and periarterial nerve stimulation. Four alpha-adrenoceptor agonists and tyramine induced vasoconstrictions in a dose-dependent manner, and the order of potency was noradrenaline (NA) > phenylephrine > clonidine > methoxamine > tyramine. Xylazine (a selective alpha 2-adrenoceptor agonist) did not elicit any vasoconstriction. Several autacoids and KCl also constricted the splenic artery dose-dependently, and the order of potency was 5-hydroxytryptamine (5-HT) >> ATP = histamine >> KCl. The dose-response curves for clonidine and NA were shifted to the right by bunazosin (a selective alpha 1-adrenoceptor antagonist), but were not affected by midaglizole (a selective alpha 2-adrenoceptor antagonist). The parameters of electrical stimulation to elicit a clear and constant vasoconstriction were 0.2 msec of pulse duration, 6 V and 0.1 Hz. The vasoconstrictive responses to electrical stimulation at 6-12 V, 0.1-10 Hz and 0.2-1 msec of pulse duration were completely inhibited by tetrodotoxin (TTX) and strongly inhibited by guanethidine. The results in this study suggest that: 1) in contrast with other regional arteries, the canine splenic artery has an alpha 1-adrenoceptor-related and clonidine-sensitive vasoconstrictive response, 2) this artery has no functional postsynaptic alpha 2-adrenoceptors, 3) it may be easier to observe the vascular responses to vasoactive agents in the isolated and perfused arterial segments, and 4) the isolated and perfused canine splenic artery is useful as a preparation to study the sympathetic nerve transmission.
authors.affiliation: Department of Pharmacology, Shinshu University School of Medicine, Matsumoto, Japan.
authors.forename: L M
authors.initials: LM
authors.lastname: Ren
authors.forename: T
authors.initials: T
authors.lastname: Nakane
authors.forename: S
authors.initials: S
authors.lastname: Chiba
mesh_terms: D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D004285:Dogs; D004558:Electric Stimulation; D005260:Female; D007093:Imidazoles / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009638:Norepinephrine / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology; D013157:Splenic Artery / Q000187:drug effects / Q000502:physiology*; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D007093:Imidazoles; D011799:Quinazolines; D014662:Vasoconstrictor Agents; C032368:midaglizole; C018176:bunazosin; D003000:Clonidine; D009638:Norepinephrine