inflammatory response, disseminated intravascular coagulation and lactic acidosis have been shown to correlate with mortality in patients with septic shock. Previous studies in our laboratory have shown that induced mild hypothermia significantly increased the survival of septic rat. Trying to explain how hypothermia could slow down the progression of sepsis, we measured arterial blood gas (PaO 2 , PaCO 2 ), pH, [HCO 3 - ], haemoglobin content as well as plasma lactates and cytokines (IL6 and TNF alpha) as indices of oxygenation status, ventilatory efficiency, acid–base balance, energy metabolism and inflammatory state. The study was conducted using 84 male Sprague–Dawley rats which were anaesthetized and maintained under normothermic (38 °C) or mild hypothermic (34 °C) conditions. Rats were assigned to one of four groups (septic + hypothermia, sham-control + hypothermia, septic + normothermia and sham-control+normothermia). Sepsis was experi- mentally induced by a cecal ligation and puncture (CLP). The sham- control groups underwent the same procedures but the cecum was neither ligated nor incised. At T0 and after 2, 4 or 6 h, rats were sacrificed and the arterial blood immediately withdrawn for assays. It is expected that our results, correlating the induced hypother- mia with blood chemistry and oxygenation conditions, will reinforce the take care of sepsis patients in intensive care units. Email Address for correspondence: karelle.leon@univ-brest.fr doi:10.1016/j.cbpa.2009.04.150 A5.64 Poster Session — Monday 29th June 2009 Autonomic regulation of the heart during digestion and swim- ming in the European sea bass (Dicentrarchus labrax) Nina K. Iversen (Aarhus University), Aurélie Prinet (Université Montpellier 2), Inge Findorf (Aarhus University), David McKenzie (Université Montpellier 2), Tobias Wang (Aarhus University) The cardiovascular responses to digestion and exercise and their autonomic regulation were studied in the European sea bass (Dicebtrarchus labrax). We measured cardiac output (Q), heart rate (f H ) and oxygen consumption (MO 2 ) at rest and during digestion or exercise and inhibited the autonomic innervation of the heart by intraperitoneal infusion of antagonists (β-adrenergic, propranolol and muscarinic cholinoceptor, atropine, 5 mg kg - 1 each). Digestion was associated with a pronounced tachycardia, a decrease in stroke volume (Vs), resulting in a slight elevation of Q (61.9±5.5 to 68.0± 5.4 ml min -1 kg -1 ) compared to rest. Swimming caused a marked increase in Q (42.7±6.3 to 60.9±3.6 ml min -1 kg -1 ) with in- creasing swimming speed (20 to 60 cm s -1 ), through a rise in f H while Vs did not change. Resting heart rate was characterized by a pronounced inhibitory vagal tone (98.3±21.7%), and the elevation in heart rate when metabolism increased was mainly due to a reduction of the vagal tone. Thus, adrenergic tone remained at 30–40% during rest, exercise and digestion. Intrinsic f H , revealed after double autonomic blockade was similar during rest and digestion (71.1 ± 4.5 and 69.8 ±6.3 min -1 ). This demonstrates that non-adrenergic, non-cholinergic (NANC) factors are of little importance in mediating the heart rate response to digestion in this species, it may be mechanical distention of the stomach wall which mediates the decreased cholinergic tone. Email Address for correspondence: nina.iversen@biology.au.dk doi:10.1016/j.cbpa.2009.04.151 A5.65 Poster Session — Monday 29th June 2009 Bimodal regulation of heart rate during hypoxic bradycardia in rainbow trout Oncorhynchus mykiss Mikkel Boel (Zoophysiology Dept. of Biological Sciences, Aarhus University), Hans Malte (Zoophysiology Dept. of Biological Sciences, Aarhus University) Rainbow trout were acclimated to normoxia or severe hypoxia (25% O 2 saturation) and subsequently exposed to various degrees of hypoxia ranging from 90%–25% while the ECG and buccal pressure was recorded. The severity of the hypoxic exposure was intensified in a stepwise manner in stages of 40 min duration. The classical responses to hypoxia, i.e. progressive increases in ventilation rate (fR) and amplitude as well as bradycardia, were observed in both acclimation groups, even though bradycardia, appeared only at the more severe hypoxia levels (40% and 25%). However, histograms of the distribution of the beat to beat intervals (H–H) revealed that, in most individuals of both acclimation groups, regulation of the heart occurred at less severe hypoxia levels. Thus, in normoxic exposures, there was a unimodal H–H distribution which, under moderate hypoxia levels, became narrower and progressively moved to shorter H–H intervals (tachycardia). At a hypoxia level around 60% or 50% a second peak of larger H–H intervals appeared, which gradually grew, while the preceding peak of smaller H–H intervals gradually became smaller. At return to normoxia the original, unimodal distribution was re-established. Thus, it seems that bradycardia results from a shifting balance between groups of H–H intervals. Email Address for correspondence: hans.malte@biology.au.dk doi:10.1016/j.cbpa.2009.04.152 A5.66 Poster Session — Monday 29th June 2009 Postprandial cardiac constancy in ball pythons, Python regius Bjarke Jensen (Aarhus University) Pythons are renowned for their pronounced metabolic response to digestion and a marked growth of the visceral organs during the postprandial period. The heart of Burmese pythons (Python molurus) may grow by up to 40% 48 h after ingestion of large meals, but very little is known about possible changes in the gross morphology. To investigate whether the morphology of the python heart changes during digestion (fed 25% of their body mass), we compared heart structure of ball pythons (Python regius) during fasting and at 24 and 48 h into the postprandial period (N = 5 in each group). Dry mass of the small intestine (SI), kidneys (K) and liver (L) increased significantly during digestion (48 h to fasting relative organ dry- weight increase was; SI=157.2%; K=47.3%; L=47.5%; N =5 per group). However, there was no significant changes in cardiac ventricular dimensions (length, width and volume; N = 5 per group) or wet mass relative to body mass (fasting, 0.27%; 24 h, 0.27%; 48 h, 0.28%; N =3 per group). The hearts were sectioned in 2 mm transverse slices (10–12 slices per ventricle) to inspect the three major ventricular septa, the muscular ridge, the bulbuslamelle and the vertical septum that are responsible for the unique pressure separation of pythons. None of the septa showed distinct changes. It appears that the postprandial cardiac growth is less pronounced in ball pythons compared to Burmese pythons and we speculate that the Abstracts / Comparative Biochemistry and Physiology, Part A 153 (2009) S90–S113 S108