Purinergic mechanisms

Scislo TJ, O Leary DS. Purinergic mechanisms of the nucleus of the solitary tract and neural cardiovascular control. Neurol Res. 2005 27 182-194. 

At the same time, ATP comes into play as a neurotransmitter, but experimental data suggest a complex mechanism of interactions. Spyer et al. (2004) proposed ATP as the key neurotransmitter, but that the CO2 response is not affected by PPADS (ATP antagonist) in in vitro preparation. Additionally, recent data from P2X2 knockout mice showed a normal response to CO2, suggesting that purinergic mechanisms are not involved in central chemo reception. However, this leaves out a role of CO2/H sensing in the peripheral chemoreceptors. 

Bumstock, G. (1990) Overview. Purinergic mechanisms. Annals of the New York Academy of Sciences, 603 1-17. 

Somlyo You showed that there are other mechanisms that come into play, such as Ca2+ sensitization. I would expect an agonist such as a purinergic agonist to activate the Rho/Rho kinase system, which ionomycin does not. 

R.aeymaek.ers Mechanical stimulation of cells in culture has been shown to release ATP which could diffuse to neighbouring cells and activate purinergic receptors. Can you exclude this possibility in the interpretation of your data ... 

Gorodeski GI, Hopfer U, and Wenwu J [1998] Purinergic receptor induced changes in paracellular resistance across cultures of human cervical cells are mediated by two distinct cytosolic calcium related mechanisms. Cell Biochem Biophys 29 281-306... 

Gorodeski GI [2002] Regulation of transcervical permeability by two distinct P2-purinergic receptor mechanisms. Am J Physiol 282 C75-C83... 

It has also been established that the RBC itself could act as a mobile sensor for hypoxia [61]. The mechanism works as follows Under conditions of low oxygen and pH, the RBC releases ATP, which binds to purinergic receptors on the endothelial cells. This leads to the production in the endothelial cells of the vasodilator NO. Since the most likely location for hypoxia would be in or near the venular network, the local vasodilatory response to NO is propagated to upstream vessels causing arteriolar vasodilation (see the following section on Coordination of Vasomotor Responses). 

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