title: Relative contributions of ATP and noradrenaline to the nerve evoked contraction of the rabbit jejunal artery. Dependence on stimulation parameters.
abstract: Isotonic contractions of the rabbit jejunal artery were evoked by perivascular nerve stimulation with trains of 10 or 100 stimuli at 2 Hz or 10 Hz. Short trains of stimuli elicited contractions that were totally resistant to alpha-adrenoceptor blockade (0.1 mumol/l prazosin) but blocked by alpha,beta-methylene ATP (1 mumol/l). A substantial noradrenergic component of contraction comprising about 50% of the total could be evoked by adjusting the stimulation parameters (increasing the frequency and/or number of stimuli in a train). The noradrenergic and the purinergic components are derived from sympathetic nerves as both were blocked by TTX and the adrenergic neurone blocker guanethidine (3 mumol/l). It is concluded that the contraction of the rabbit jejunal artery to short trains of stimuli is predominantly purinergic, a noradrenergic component only being revealed at higher frequencies of stimulation or during longer trains of stimuli. The purinergic component of contraction is derived from sympathetic nerves and not from a separate population of purinergic nerves.
authors.affiliation: University Department of Pharmacology, Oxford, UK.
authors.forename: R J
authors.initials: RJ
authors.lastname: Evans
authors.forename: T C
authors.initials: TC
authors.lastname: Cunnane
mesh_terms: D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology / Q000502:physiology*; D000818:Animals; D015226:Dinucleoside Phosphates / Q000494:pharmacology; D004558:Electric Stimulation; D005260:Female; D006145:Guanethidine / Q000494:pharmacology; D066298:In Vitro Techniques; D007583:Jejunum / Q000098:blood supply; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D009638:Norepinephrine / Q000494:pharmacology / Q000502:physiology*; D011224:Prazosin / Q000494:pharmacology; D011817:Rabbits; D012039:Regional Blood Flow / Q000187:drug effects / Q000502:physiology
chemical_list: D015226:Dinucleoside Phosphates; C012275:P(1),P(5)-di(adenosine-5'-)pentaphosphate; D000255:Adenosine Triphosphate; C002630:alpha,beta-methyleneadenosine 5'-triphosphate; D009638:Norepinephrine; D011224:Prazosin; D006145:Guanethidine