title: Postnatal development of excitatory innervations in longitudinal smooth muscle of the chicken anterior mesenteric artery.
abstract: OBJECTIVE
  The anterior mesenteric artery of chickens contains a well-developed outer longitudinal smooth muscle layer in addition to an inner circular layer. Cholinergic and purinergic neurons play crucial roles in excitatory transmission at the longitudinal smooth muscle. The aim of this study was to clarify postnatal development of excitatory neurotransmission of the longitudinal smooth muscle.
  
  
  METHODS
  Membrane potentials of smooth muscle were recorded with a microelectrode technique. Perivascular nerves were stimulated by applying electrical field stimulation (EFS).
  
  
  RESULTS
  Histological examination showed that longitudinal smooth muscles exist in the artery at birth. EFS failed to evoke membrane response in 1-day-old chickens, though it caused depolarization (excitatory junction potential; EJP) in 12-week-old chickens. However, exogenous application of acetylcholine (ACh) or ATP produced depolarization in longitudinal smooth muscle of 1-day-old chickens, suggesting that responsiveness of smooth muscle to excitatory neurotransmitters is already established at birth. In preparations isolated from 10-day-old chickens, EFS caused EJP, which was totally blocked by atropine but not by a non-specific purinoceptor antagonist, suramin. Several purinoceptor subtypes including P2Y1, which may be related to depolarizing response in smooth muscle of adult chickens, were expressed in the anterior mesenteric artery of 10-day-old chickens.
  
  
  CONCLUSIONS
  Excitatory innervation in longitudinal smooth muscle of the chicken anterior mesenteric artery is not established at birth but develops during the early postnatal period. Moreover, development of cholinergic excitatory innervation precedes that of purinergic excitatory innervation, although receptors that mediate purinergic control are already expressed in smooth muscle.
authors.affiliation: Department of Basic Veterinary Science, Laboratory of Physiology, The United Graduate School of Veterinary Sciences, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan.
authors.forename: Feras
authors.initials: F
authors.lastname: Alkayed
authors.forename: Takahiko
authors.initials: T
authors.lastname: Shiina
authors.forename: Tadashi
authors.initials: T
authors.lastname: Takewaki
authors.forename: Yasutake
authors.initials: Y
authors.lastname: Shimizu
mesh_terms: D000109:Acetylcholine / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001285:Atropine / Q000494:pharmacology; D002645:Chickens; D018679:Cholinergic Agonists / Q000494:pharmacology; D004558:Electric Stimulation; D008297:Male; D008564:Membrane Potentials / Q000502:physiology; D008638:Mesenteric Arteries / Q000294:innervation*; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000502:physiology*; D011950:Receptors, Cholinergic / Q000235:genetics / Q000378:metabolism*; D058472:Receptors, Purinergic P2Y1 / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055366:Synaptic Potentials / Q000187:drug effects
chemical_list: D018679:Cholinergic Agonists; D011950:Receptors, Cholinergic; D058472:Receptors, Purinergic P2Y1; D001285:Atropine; D000255:Adenosine Triphosphate; D000109:Acetylcholine