Long-term facilitation of upper airway muscle activity induced by episodic upper airway negative pressure and hypoxia in spontaneously breathing anaesthetised rats. Export

@article{citeulike:4277652, abstract = {ABSTRACT Obstruction of the upper airway (UA) is associated with episodes of hypoxia and upper airway negative pressure (UANP). Episodic hypoxia elicits long-term facilitation (LTF) of tongue protrudor, retractor and respiratory pump muscle activity (Ryan et al paper submitted). However, whether repeated exposure to UANP also induces LTF is unknown. We hypothesised that repetitive exposure to UANP would induce LTF of UA and respiratory pump muscle activity and when coupled with hypoxia, as occurs when the UA obstructs, would lead to an even greater facilitation of muscle activity and the response to UANP. Experiments were performed in 24 anaesthetised, spontaneously breathing rats with intact vagi. To induce LTF, UANP stimuli (-10cmH(2)O) of 5-second duration were delivered every 30 seconds for three minutes ([\&plusmn] hypoxia). This was repeated eight times over one hour, each three-minute episode separated by five minutes normoxia. Genioglossus (GG), hyoglossus (HG) and diaphragm (Dia) muscle activity was recorded before, during and for one hour following the last exposure to episodic UANP alone (n = 8), UANP and hypoxia together (n = 8) or normoxia alone (n = 8). During the final hour, single pulses of UANP were applied at 1 minute and every 10 minutes thereafter to determine whether LTF of the response to UANP had been induced. Our results show that LTF of GG muscle activity and its response to UANP was induced following exposure to episodic UANP stimuli alone and UANP applied during hypoxia. However, there was no significant difference between these responses. Episodic UANP alone also induced LTF of HG muscle activity but this effect did not manifest until 40 minutes following the last episode of repeated UANP stimulation. In the presence of hypoxia, no LTF of HG muscle response to UANP was found. In conclusion, episodic UANP stimulation induces LTF of UA dilator and retractor tongue muscles, but no further facilitation occurs when coupled with hypoxia. This response may serve as an important protective mechanism of respiratory homeostasis during sleep, particularly in patients who suffer from obstructive sleep apnoea.}, author = {Ryan, Stephen and Nolan, Philip}, citeulike-article-id = {4277652}, citeulike-linkout-0 = {http://dx.doi.org/10.1113/jphysiol.2009.169698}, citeulike-linkout-1 = {http://view.ncbi.nlm.nih.gov/pubmed/19332494}, citeulike-linkout-2 = {http://www.hubmed.org/display.cgi?uids=19332494}, day = {30}, doi = {10.1113/jphysiol.2009.169698}, issn = {1469-7793}, journal = {The Journal of physiology}, keywords = {breathing, f1000, sleep}, month = {March}, posted-at = {2009-06-22 21:08:54}, priority = {2}, title = {Long-term facilitation of upper airway muscle activity induced by episodic upper airway negative pressure and hypoxia in spontaneously breathing anaesthetised rats.}, url = {http://dx.doi.org/10.1113/jphysiol.2009.169698}, year = {2009} }

TY - JOUR ID - citeulike:4277652 L3 - citeulike-article-id:4277652 N2 - ABSTRACT Obstruction of the upper airway (UA) is associated with episodes of hypoxia and upper airway negative pressure (UANP). Episodic hypoxia elicits long-term facilitation (LTF) of tongue protrudor, retractor and respiratory pump muscle activity (Ryan et al paper submitted). However, whether repeated exposure to UANP also induces LTF is unknown. We hypothesised that repetitive exposure to UANP would induce LTF of UA and respiratory pump muscle activity and when coupled with hypoxia, as occurs when the UA obstructs, would lead to an even greater facilitation of muscle activity and the response to UANP. Experiments were performed in 24 anaesthetised, spontaneously breathing rats with intact vagi. To induce LTF, UANP stimuli (-10cmH(2)O) of 5-second duration were delivered every 30 seconds for three minutes ([&plusmn] hypoxia). This was repeated eight times over one hour, each three-minute episode separated by five minutes normoxia. Genioglossus (GG), hyoglossus (HG) and diaphragm (Dia) muscle activity was recorded before, during and for one hour following the last exposure to episodic UANP alone (n = 8), UANP and hypoxia together (n = 8) or normoxia alone (n = 8). During the final hour, single pulses of UANP were applied at 1 minute and every 10 minutes thereafter to determine whether LTF of the response to UANP had been induced. Our results show that LTF of GG muscle activity and its response to UANP was induced following exposure to episodic UANP stimuli alone and UANP applied during hypoxia. However, there was no significant difference between these responses. Episodic UANP alone also induced LTF of HG muscle activity but this effect did not manifest until 40 minutes following the last episode of repeated UANP stimulation. In the presence of hypoxia, no LTF of HG muscle response to UANP was found. In conclusion, episodic UANP stimulation induces LTF of UA dilator and retractor tongue muscles, but no further facilitation occurs when coupled with hypoxia. This response may serve as an important protective mechanism of respiratory homeostasis during sleep, particularly in patients who suffer from obstructive sleep apnoea. JF - The Journal of physiology SN - 1469-7793 TI - Long-term facilitation of upper airway muscle activity induced by episodic upper airway negative pressure and hypoxia in spontaneously breathing anaesthetised rats. KW - breathing KW - f1000 KW - sleep AU - Ryan, Stephen AU - Nolan, Philip PY - 2009/03/30/ UR - http://dx.doi.org/10.1113/jphysiol.2009.169698 ER -