title: Frequency-dependence of 3H-noradrenaline release from rabbit pulmonary artery: effect of alpha-adrenoceptor antagonists and inhibitors of transmitter inactivation.
abstract: The aim of this study was to examine the modulating role of presynaptic alpha 2-adrenoceptors on transmitter release from vascular sympathetic neurones. This was done by examining the influence of removal of inactivation pathways on the effect of alpha-adrenoceptor antagonists on the release of transmitter from noradrenergic neurones. The rabbit main pulmonary artery preloaded with 3H-noradrenaline (3H-NA) was used. The artery was stimulated with 300 pulses at various frequencies (1, 3, 10 and 30 Hz). Pargyline (3 x 10(-4) M) increased the stimulation-evoked 3H-overflow at 1 and 3 Hz and decreased it at 30 Hz. U-0521 (3',4'-dihydroxy-2-methylpropiophenone; 3 x 10(-6) M) enhanced the overflow at 1 Hz and had no effect at 3-30 Hz. Corticosterone (4 x 10(-5) M) did not alter the stimulation-evoked 3H-overflow at 1-30 Hz. Cocaine (3 x 10(-6) M) enhanced the 3H-overflow slightly at 1-30 Hz. At 3 x 10(-5) M, cocaine enhanced 3H-overflow at 1 Hz and reduced it at 30 Hz. Neither corticosterone (4 x 10(-5) M) nor propranolol (10(-7) M) modified this effect of cocaine. Propranolol (10(-7) M) alone decreased the 3H-overflow at 30 Hz and had no effect at 1-10 Hz. Phenoxybenzamine (10(-6) M) and chlorpromazine (3 x 10(-6) M) potentiated the stimulation-evoked 3H-overflow at 1-30 Hz.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, School of Medicine, Odense University, Denmark.
authors.forename: O A
authors.initials: OA
authors.lastname: Nedergaard
mesh_terms: D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D003345:Corticosterone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004558:Electric Stimulation; D066298:In Vitro Techniques; D009474:Neurons / Q000378:metabolism; D014179:Neurotransmitter Uptake Inhibitors / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D011619:Psychotropic Drugs / Q000494:pharmacology; D011651:Pulmonary Artery / Q000294:innervation; D011817:Rabbits; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*; D014316:Tritium
chemical_list: D000317:Adrenergic alpha-Antagonists; D014179:Neurotransmitter Uptake Inhibitors; D011619:Psychotropic Drugs; D011942:Receptors, Adrenergic, alpha; D014316:Tritium; D003345:Corticosterone; D009638:Norepinephrine