title: Hypothermia reduces ischemia- and stimulation-induced myocardial interstitial norepinephrine and acetylcholine releases.
abstract: Although hypothermia is one of the most powerful modulators that can reduce ischemic injury, the effects of hypothermia on the function of the cardiac autonomic nerves in vivo are not well understood. We examined the effects of hypothermia on the myocardial interstitial norepinephrine (NE) and ACh releases in response to acute myocardial ischemia and to efferent sympathetic or vagal nerve stimulation in anesthetized cats. We induced acute myocardial ischemia by coronary artery occlusion. Compared with normothermia (n = 8), hypothermia at 33 degrees C (n = 6) suppressed the ischemia-induced NE release [63 nM (SD 39) vs. 18 nM (SD 25), P < 0.01] and ACh release [11.6 nM (SD 7.6) vs. 2.4 nM (SD 1.3), P < 0.01] in the ischemic region. Under hypothermia, the coronary occlusion increased the ACh level from 0.67 nM (SD 0.44) to 6.0 nM (SD 6.0) (P < 0.05) and decreased the NE level from 0.63 nM (SD 0.19) to 0.40 nM (SD 0.25) (P < 0.05) in the nonischemic region. Hypothermia attenuated the nerve stimulation-induced NE release from 1.05 nM (SD 0.85) to 0.73 nM (SD 0.73) (P < 0.05, n = 6) and ACh release from 10.2 nM (SD 5.1) to 7.1 nM (SD 3.4) (P < 0.05, n = 5). In conclusion, hypothermia attenuated the ischemia-induced NE and ACh releases in the ischemic region. Moreover, hypothermia also attenuated the nerve stimulation-induced NE and ACh releases. The Bezold-Jarisch reflex evoked by the left anterior descending coronary artery occlusion, however, did not appear to be affected under hypothermia.
authors.affiliation: Dept. of Cardiovascular Dynamics, Advanced Medical Engineering Center, National Cardiovascular Center Research Institute, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan. torukawa@res.ncvc.go.jp
authors.forename: Toru
authors.initials: T
authors.lastname: Kawada
authors.forename: Hirotoshi
authors.initials: H
authors.lastname: Kitagawa
authors.forename: Toji
authors.initials: T
authors.lastname: Yamazaki
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Akiyama
authors.forename: Atsunori
authors.initials: A
authors.lastname: Kamiya
authors.forename: Kazunori
authors.initials: K
authors.lastname: Uemura
authors.forename: Hidezo
authors.initials: H
authors.lastname: Mori
authors.forename: Masaru
authors.initials: M
authors.lastname: Sugimachi
mesh_terms: D000109:Acetylcholine / Q000378:metabolism*; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D002415:Cats; D004558:Electric Stimulation; D006339:Heart Rate / Q000502:physiology; D007035:Hypothermia / Q000378:metabolism*; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D009638:Norepinephrine / Q000378:metabolism*; D013564:Sympathetic Nervous System / Q000502:physiology*; D014630:Vagus Nerve / Q000502:physiology*
chemical_list: D000109:Acetylcholine; D009638:Norepinephrine