caa a22 4500 467941572 CHVBK 20180406153014.0 cr unu---uuuuu 170328e20060501xx s 000 0 eng 10.1007/s00421-006-0135-7 doi (NATIONALLICENCE)springer-10.1007/s00421-006-0135-7 Hormonal responses to opioid receptor blockade: during rest and exercise in cold and hot environments [Elektronische Daten] [David Armstrong III, Bradley Hatfield] Opioid receptors appear to modulate a variety of physiological and metabolic homeostatic responses to stressors such as exercise and thermally extreme environments. To more accurately determine the role of the naloxone (NAL) sensitive opioid receptor system during rest and exercise, subjects were subjected to concomitant environmental thermal stress. Fifteen untrained men rested or performed low intensity (60% $$ V_{{{\text{O}}_{{{\text{2peak}}}} }} $$ ) or high intensity (80% $$ V_{{{\text{O}}_{{{\text{2peak}}}} }} $$ ) exercise on a cycle ergometer for 60min in an environmental chamber during cold (0°C) hot (35°C) air exposure while receiving an infusion of normal saline (SAL) or NAL (0.1mgkg−1). Plasma adrenocorticotropin hormone (ACTH), immunoreactive beta-endorphin (IBE), cortisol and growth hormone were measured at baseline and every 15min while in the chamber. Time to exhaustion was significantly reduced during high intensity exercise in the heat (P<0.0001). NAL significantly (P=0.0004) reduced the time to exhaustion (38.3±2.1min) during high intensity exercise in the heat compared to SAL (49.4±2.1min). ACTH and IBE increased during hot conditions and cold attenuated this response. Plasma concentrations of IBE, ACTH, and growth hormone increased significantly with NAL during high intensity exercise in the heat compared to SAL. Cold attenuated the response of ACTH, IBE and cortisol to NAL. NAL administration exaggerates plasma hormone concentration during high intensity exercise in the heat, but not cold. These results support a regulatory effect of the opioid receptor system on physiological responses during exercise in thermally stressful environments. Future research should be directed to more clearly defining the effect of environmental temperature on the mechanism of hypothalamic-pituitary-adrenal hormonal release during exercise and hot environmental temperatures. Springer-Verlag, 2006 Exercise nationallicence Men nationallicence Cold nationallicence Heat nationallicence Naloxone nationallicence Opioid receptors nationallicence Armstrong III David Department of Internal Medicine, Endocrinology Clinic, National Naval Medical Center, 20814, Bethesda, MD, USA aut Hatfield Bradley Deptartment of Kinesiology, University of Maryland, North Gym, College Park, MD, USA aut European Journal of Applied Physiology Springer-Verlag 97/1(2006-05-01), 43-51 1439-6319 97:1<43 2006 97 421 https://doi.org/10.1007/s00421-006-0135-7 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00421-006-0135-7 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Armstrong III David Department of Internal Medicine, Endocrinology Clinic, National Naval Medical Center, 20814, Bethesda, MD, USA aut NATIONALLICENCE 700 1- Hatfield Bradley Deptartment of Kinesiology, University of Maryland, North Gym, College Park, MD, USA aut NATIONALLICENCE 773 0- European Journal of Applied Physiology Springer-Verlag 97/1(2006-05-01), 43-51 1439-6319 97:1<43 2006 97 421 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer