Release of ATP in the ventral medulla during hypoxia in rats: role in hypoxic ventilatory response.
P2X2 receptor subunits of the ATP-gated ion channels are expressed by physiologically identified respiratory neurons in the ventral respiratory column, implicating ATP in the control of respiratory activity. We now show that, during hypoxia, release of ATP in the ventrolateral medulla (VLM) plays an important role in the hypoxic ventilatory response in rats. By measuring ATP release in real time at the ventral surface of the medulla with novel amperometric biosensors, we found that hypoxia (10% O2; 5 min) induced a marked increase in the concentration of ATP (approximately 3 microm). This ATP release occurred after the initiation of enhanced respiratory activity but coincided with the later hypoxia-induced slowing of the respiratory rhythm. ATP was also released at the ventral surface of the medulla during hypoxia in peripherally chemodenervated animals (vagi, aortic, and carotid sinus nerve sectioned). By using horizontal slices of the rat medulla, we found that, during hypoxia, ATP is produced throughout the VLM in the locations corresponding to the ventral respiratory column. Blockade of ATP receptors in the VLM (microinjection of P2 receptor antagonist pyridoxal-5'-phosphate-6-azophenyl-2',4'-disulphonic acid; 100 mum) augmented the hypoxia-induced secondary slowing of the respiratory rhythm. Our findings suggest that ATP released within the ventral respiratory column is involved in maintenance of the respiratory activity in conditions when hypoxia-induced slowing of respiration occurs. These data illustrate a new functional role for ATP-mediated purinergic signaling in the medullary mechanisms controlling respiratory activity.
Gourine
Alexander V
AV
Department of Physiology, Royal Free and University College Medical School, London NW3 2PF, United Kingdom. a.gourine@rfc.ucl.ac.uk
Llaudet
Enrique
E
Dale
Nicholas
N
Spyer
K Michael
KM
D000222:Adaptation, Physiological; D000255:Adenosine Triphosphate / Q000378:metabolism*; D000818:Animals; D015374:Biosensing Techniques; D000860:Hypoxia / Q000503:physiopathology*; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism*; D010791:Phrenic Nerve / Q000503:physiopathology; D011732:Pyridoxal Phosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018048:Receptors, Purinergic P2 / Q000187:drug effects / Q000502:physiology; D058476:Receptors, Purinergic P2X2; D012143:Respiratory Physiological Phenomena; D015398:Signal Transduction / Q000187:drug effects; D013563:Sympathectomy, Chemical
C546403:P2rx2 protein, rat; D018048:Receptors, Purinergic P2; D058476:Receptors, Purinergic P2X2; C077792:pyridoxal phosphate-6-azophenyl-2',4'-disulfonic acid; D011732:Pyridoxal Phosphate; D000255:Adenosine Triphosphate