title: Purinergic Ca2+ signaling in myenteric neurons via P2 purinoceptors.
abstract: Fura 2 microfluorimetry was used to test the hypothesis that ATP acts at P1 and P2 purinoceptors to elevate cytosolic free Ca2+ concentrations [Ca2+]i) in calbindin-immunoreactive cultured myenteric neurons from adult guinea pig small intestine. Local "micro-puff" application of ATP or ATP(gamma)S caused an increase in [Ca2+]i in 99% of 200 multipolar neurons. The potency profile of agonists for the rise in [Ca2+]i was ATP(gamma)S = ATP >> ADP >> AMP, adenosine, 5'-(N-ethylcarboxamido)adenosine, and 2-chloro-N(6)-cyclopentyladenosine. Tetrodotoxin-sensitive synaptic transmission could contribute as much as 25% to the ATP response. The P1 antagonist 8-cyclopentyl-1,3-dipropylxanthine blocked 50% of the peakATP Ca2+ response. P2 antagonists blocked the ATP response: pyridoxalphosphate-6-azophenyl-2',4'-disulfonic acid > reactive blue 2 > suramin. Suramin enhanced the ATP response in 27.5% of neurons. Some neurons (<15%) displayed distinct multiphasic Ca2+ signatures. About 54% of ATP-responsive neurons expressed calbindin. The data support the following hypotheses: 1) two distinct P2 purinoceptors are linked to the rise in [Ca2+]i in myenteric neurons; 2) purinergic Ca2+ signaling is not restricted to one neuronal phenotype; and 3) intraneuronal Ca2+ is not involved in adenosinergic hyperpolarization in AH/type 2 neurons.
authors.affiliation: Department of Anesthesiology, College of Medicine, The Ohio State University, Columbus 43210, USA.
authors.forename: F L
authors.initials: FL
authors.lastname: Christofi
authors.forename: Z
authors.initials: Z
authors.lastname: Guan
authors.forename: J D
authors.initials: JD
authors.lastname: Wood
authors.forename: L V
authors.initials: LV
authors.lastname: Baidan
authors.forename: B T
authors.initials: BT
authors.lastname: Stokes
mesh_terms: D000241:Adenosine / Q000502:physiology; D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D064026:Calbindins; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D017615:Enteric Nervous System / Q000166:cytology / Q000502:physiology*; D006168:Guinea Pigs; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D015398:Signal Transduction; D013329:Structure-Activity Relationship; D013498:Suramin / Q000494:pharmacology; D013779:Tetrodotoxin / Q000494:pharmacology
chemical_list: D064026:Calbindins; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D064030:S100 Calcium Binding Protein G; D013779:Tetrodotoxin; D013498:Suramin; D000255:Adenosine Triphosphate; D000241:Adenosine; D002118:Calcium