Beta-nicotinamide adenine dinucleotide is an inhibitory neurotransmitter in visceral smooth muscle.
Peripheral inhibitory nerves are physiological regulators of the contractile behavior of visceral smooth muscles. One of the transmitters responsible for inhibitory neurotransmission has been reputed to be a purine, possibly ATP. However, the exact identity of this substance has never been verified. Here we show that beta-nicotinamide adenine dinucleotide (beta-NAD), an inhibitory neurotransmitter candidate, is released by stimulation of enteric nerves in gastrointestinal muscles, and the pharmacological profile of beta-NAD mimics the endogenous neurotransmitter better than ATP. Levels of beta-NAD in superfusates of muscles after nerve stimulation exceed ATP by at least 30-fold; unlike ATP, the release of beta-NAD depends on the frequency of nerve stimulation. beta-NAD is released from enteric neurons, and release was blocked by tetrodotoxin or omega-conotoxin GVIA. beta-NAD is an agonist for P2Y1 receptors, as demonstrated by receptor-mediated responses in HEK293 cells expressing P2Y1 receptors. Exogenous beta-NAD mimics the effects of the enteric inhibitory neurotransmitter. Responses to beta-NAD and inhibitory junction potentials are blocked by the P2Y1-selective antagonist, MRS2179, and the nonselective P2 receptor antagonists, pyridoxal phosphate 6-azophenyl-2',4'-disulfonic acid and suramin. Responses to ATP are not blocked by these P2Y receptor inhibitors. The expression of CD38 in gastrointestinal muscles, and specifically in interstitial cells of Cajal, provides a means of transmitter disposal after stimulation. beta-NAD meets the traditional criteria for a neurotransmitter that contributes to enteric inhibitory regulation of visceral smooth muscles.
Mutafova-Yambolieva
Violeta N
VN
Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV 89557, USA.
Hwang
Sung Jin
SJ
Hao
Xuemei
X
Chen
Hui
H
Zhu
Michael X
MX
Wood
Jackie D
JD
Ward
Sean M
SM
Sanders
Kenton M
KM
D000244:Adenosine Diphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D004558:Electric Stimulation; D006801:Humans; D066298:In Vitro Techniques; D051379:Mice; D008810:Mice, Inbred C57BL; D009130:Muscle, Smooth / Q000187:drug effects / Q000294:innervation*; D009243:NAD / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology*; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2 / Q000235:genetics / Q000502:physiology; D058472:Receptors, Purinergic P2Y1; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism
C111914:N(6)-methyl-2'-deoxyadenosine 3',5'-diphosphate; D018377:Neurotransmitter Agents; C546382:P2RY1 protein, human; C546383:P2ry1 protein, mouse; D058919:Purinergic P2 Receptor Antagonists; D018048:Receptors, Purinergic P2; D058472:Receptors, Purinergic P2Y1; D011994:Recombinant Proteins; D009243:NAD; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate