Purinergic ca2+ signaling in myenteric neurons via p2
purinoceptors.
Christofi, F. L., Z. Guan, J. D. Wood, L. V. Baidan, and B. T. Stokes.
Departments of Anesthesiology and Physiology, College of Medicine,
The Ohio State University, Columbus, OH 43210, USA
APStracts 3:0177G, 1996.
Fura-2 microfluorimetry was used to test the hypothesis that ATP acts
at P1 and P2 purinoceptors to elevate cytosolic free Ca2+ levels
([Ca2+]i) in calbindin immunoreactive cultured myenteric neurons from
adult guinea-pig small intestine. Local "micropuff"
application of ATP or ATP[tau]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[tau]S = ATP >> ADP >>
AMP, Adenosine, NECA, CCPA. TTX-sensitive synaptic transmission could
contribute as much as 25% to the ATP response. The P1 antagonist
CPDPX blocked 50% of the peak ATP Ca2+ response. P2 antagonists
blocked the ATP response; PPADS > 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
supports 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. [3] Intraneuronal Ca2+ is not involved in adenosinergic
hyperpolarization in AH/Type 2 neurons.
Received 24 October 1995; accepted in final form 5 September
1996.
APS Manuscript Number G461-5.
Article publication pending Am. J. Physiol. (Gastrointest. Liver
Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996