title: Influence of age on control of norepinephrine release: Ca2+ channels and dopamine D2 receptors.
abstract: Possible age-related changes in the roles of L- and N-type Ca2+ channels and dopamine D2 receptors in control of norepinephrine release were investigated in tail arteries of F-344 rats. Nifedipine had no effect on stimulation-evoked tritium efflux at 6 or 24 months of age; however, omega-conotoxin GVIA reduced efflux by 70 to 80% at both ages even when frequency of stimulation was altered. Activation of prejunctional dopamine D2 receptors by the selective agonist N-0923 [(S)-(-)-2-(N-propyl-N-2-thienylethylamino)-5-hydroxytetralin++ +] inhibited contractile responses to transmural nerve stimulation in a frequency and concentration-dependent manner. Effects were similar from 6 to 26 months. Furthermore inhibition by N-0923 of stimulation-evoked [3H]norepinephrine efflux was not different at 12 and 24 months. Thus, N-type Ca2+ channels predominate in control of norepinephrine release, and this is unchanged with advancing age or stimulation intensity. Furthermore, D2 receptor-mediated inhibition of norepinephrine release is not altered with advancing age.
authors.affiliation: Department of Pharmacology, College of Medicine, University of California, Irvine 92717.
authors.forename: D J
authors.initials: DJ
authors.lastname: Friedman
authors.forename: S P
authors.initials: SP
authors.lastname: Duckles
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D001158:Arteries / Q000294:innervation; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D015259:Dopamine Agents / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000294:innervation; D009543:Nifedipine / Q000494:pharmacology; D009638:Norepinephrine / Q000378:metabolism*; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D017448:Receptors, Dopamine D2 / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000187:drug effects / Q000378:metabolism*; D013623:Tail / Q000098:blood supply; D013764:Tetrahydronaphthalenes / Q000494:pharmacology; D013876:Thiophenes / Q000494:pharmacology; D020866:omega-Conotoxin GVIA
chemical_list: D002121:Calcium Channel Blockers; D015220:Calcium Channels; D015259:Dopamine Agents; D010455:Peptides; D017448:Receptors, Dopamine D2; D013764:Tetrahydronaphthalenes; D013876:Thiophenes; C047508:rotigotine; D020866:omega-Conotoxin GVIA; D009543:Nifedipine; D009638:Norepinephrine