Respiratory and Circulatory Responses of Rainbow Trout Larvae to Carbon Monoxide and to Hypoxia

1971 ◽  
Vol 55 (3) ◽  
pp. 683-694
Author(s):  
G. F. HOLETON
Keyword(s):  
Heart Rate ◽  
Carbon Monoxide ◽  
Rainbow Trout ◽  
Vagal Tone ◽  
Resting Heart Rate ◽  
Adult Fish ◽  
Cutaneous Respiration

1. Larval trout undergo a transition from cutaneous respiration to gill respiration which at 10°C is well advanced by the 18th day after hatching. 2. Resting heart rate of newly hatched trout increases during the first few days, stabilizes for a while, and then drops between the 9th and 18th day after hatching. This drop may be the result of establishment of ‘vagal tone’. 3. The basic breathing response of larval trout when hypoxic is an increase in fin movements and an increase in rate and amplitude of breathing, but breathing movements slow and weaken if environmental PO2 falls much below 40 mmHg. 4. With trout up to 8 days after hatching hypoxia causes a tachycardia. At very low PO2 levels there is a drop in heart rate and in the amount of blood pumped by the heart. Upon restoring oxygen to very hypoxic larvae, the heart rate recovers slowly, unlike the quick abolition of bradycardia of adult fish. It appears that up to the age of 8 days from hatching, trout do not have a functional bradycardia reflex associated with hypoxia. 5. The responses of larval trout to CO and to hypoxia, and of adult trout to CO, are similar in nature. It is proposed that the basic response to anoxaemia is an increase in breathing and circulation and that the adult bradycardia response to hypoxia is a superimposed mechanism which relates circulation to the quantity of oxygen presented to the gills.

P4423Extreme bradycardia in athletes is due to intrinsic changes within the heart

2019 ◽  
Vol 40 (Supplement_1) ◽  
Author(s):  
M D Flannery ◽  
F Sully ◽  
K Janssens ◽  
G Morris ◽  
J Kalman ◽  
...  
Keyword(s):  
Heart Rate ◽  
Vagal Tone ◽  
Endurance Athletes ◽  
Valsalva Manoeuvre ◽  
Resting Heart Rate ◽  
Maximum Heart Rate ◽  
Vo2 Max ◽  
Heart Rates ◽  
Intrinsic Heart Rate ◽  
Autonomic Blockade

Abstract Background It is well known that athletes and in particular endurance athletes have lower resting heart rates than non-athletes. This has generally been considered a healthy adaptation. Traditionally this was thought be due to increased vagal tone. Several studies have shown that endurance athletes continue to have lower heart rates in the absence of autonomic influence suggesting bradycardia is due to intrinsic changes within the heart. A subset of endurance athletes have very low heart rates with Tour de France cyclists having described heart rates in the 30s. It is unclear whether in these elite athletes with very low heart rates the profound bradycardia is due to autonomic influence or intrinsic changes within the heart. Aim The aim of this study was to determine if extreme bradycardia in athletes is due to excess vagal tone or more profound intrinsic changes within the heart. Methods We recruited three cohorts for this study: non-athlete controls (NA), endurance athletes with a documented resting heart rate >40 (EA) and endurance athletes with a resting heart rate <40 (BA). All participants underwent baseline testing including ECG, echocardiography and VO2 max testing. All participants came back on a second occasion for treatment with dual autonomic blockade (DAB) to determine intrinsic heart rate in the following manner. After resting supine for five minutes resting heart rate was measured. Participants were then administered 0.04mg/kg of intravenous atropine. After five minutes participants were then administered 0.05mg/kg of intravenous metoprolol. This was repeated every five minutes until there was no further drop in heart rate or 0.2mg/kg had been administered. The resting heart rate at this stage was recorded as the intrinsic heart rate. Parasympathetic blockade was confirmed by lack of response to Valsalva manoeuvre and sympathetic blockade was confirmed by lack of response to metoprolol. VO2 max testing was then performed to determine maximum heart rate. Results 9 NA (7 male), 10 EA (8 male) and 5 BA (4 male) participated in this study. The average age was similar in all groups (NA 32.9y, EA 32.4y, BA 31.4y). The average resting heart rate was 71.7 in the NA group, 48.3 in the EA group and 41.6 in the BA group (p<0.05 for comparisons between all three groups). Following dual autonomic blockade resting heart rate was 86.0 in the NA group, 76.9 in the EA group and 64.4 in the BA group (p<0.05 for comparisons between all three groups). Maximum heart rate under DAB was 140.1 in the NA group, 138.0 in the EA group and 140.4 in the BA group. These differences were not significant. Conclusion In athletes with very low heart rates, bradycardia is due to more profound intrinsic changes within the heart. Acknowledgement/Funding NHMRC Project Grant

The influence of temperature and anaemia on the adrenergic and cholinergic mechanisms controlling heart rate in the rainbow trout

1979 ◽  
Vol 57 (12) ◽  
pp. 2440-2447 ◽  
Author(s):  
Chris M. Wood ◽  
Patricia Pieprzak ◽  
J. N. Trott
Keyword(s):  
Heart Rate ◽  
Rainbow Trout ◽  
Relative Effect ◽  
Salmo Gairdneri ◽  
Resting Heart Rate ◽  
Adrenergic Stimulation ◽  
Cholinergic Mechanisms ◽  
Cholinergic Mechanism ◽  
Cholinergic Tone ◽  
C 30

The capacity for cardioacceleration by adrenergic and cholinergic mechanisms was studied in resting rainbow trout, Salmo gairdneri, at 5, 12, and 20 °C. The trout were fitted with chronic dorsal aortic catheters for heart rate and blood pressure measurements. At all three temperatures, muscarinic cholinergic blockade with atropine caused substantial tachycardia, thereby indicating the presence of cholinergic vagal tone in resting animals. The relative effect of atropine was significantly greater at 5 °C (+53% of resting heart rate) than at 12 and 20 °C (≈ +30%). Maximal adrenergic stimulation (via adrenaline) after atropine caused a small further cardioacceleration at all temperatures. The adrenaline effect increased significantly from +8% (of resting heart rate) at 5 °C to +15% at 20 °C. The findings provide qualified support for the hypothesis that a reduction in vagal cholinergic activity is relatively more important in tachycardia at low temperature, and that adrenergic stimulation is relatively more important at high temperature, although the cardioacceleratory capacity of the cholinergic mechanism remains dominant throughout. The increase in heart rate accompanying experimental anaemia (haematocrit ≤ 6%) at all three temperatures was almost entirely due to a removal of vagal cholinergic tone; the contribution of adrenergic mechanisms, if any, was small.

scholarly journals It takes time to heal a broken heart: Ventricular plasticity improves heart performance after myocardial infarction in rainbow trout, Oncorhynchus mykiss

2021 ◽  
Author(s):  
Lucas A. Zena ◽  
Andreas Ekström ◽  
Albin Gräns ◽  
Catharina Olsson ◽  
Michael Axelsson ◽  
...  
Keyword(s):  
Heart Rate ◽  
Rainbow Trout ◽  
Coronary Artery ◽  
Oncorhynchus Mykiss ◽  
Coronary Occlusion ◽  
Morphological Characteristics ◽  
Coronary Artery Ligation ◽  
Resting Heart Rate ◽  
Rainbow Trout Oncorhynchus Mykiss

Coronary arteriosclerosis is a common feature of both wild and farmed salmonid fishes and may be linked to stress-induced cardiac pathologies. Yet, the plasticity and capacity for long-term myocardial restructuring and recovery following a restriction in coronary blood supply is unknown. Here, we analyzed the consequences of acute (3 days) and chronic (from 33 to 62 days) coronary occlusion (i.e., coronary artery ligation) on cardiac morphological characteristics and in vivo function in juvenile rainbow trout, Oncorhynchus mykiss. Acute coronary occlusion resulted in elevated resting heart rate and decreased inter-beat variability, which are both markers of autonomic dysfunction following acute myocardial ischemia, along with severely reduced heart rate scope (maximum – resting heart rate) relative to sham-operated trout. We also observed a loss of myocardial interstitial collagen and compact myocardium. Following long-term coronary- ligation, resting heart rate and heart rate scope normalized relative to sham-operated trout. Moreover, a distinct fibrous collagen layer separating the compact myocardium into two layers had formed. This may contribute to maintain ventricular integrity across the cardiac cycle, or alternatively, demark a region of the compact myocardium that continues to receive oxygen from the luminal venous blood. Taken together, we demonstrate that rainbow trout may cope with the aversive effects caused by coronary artery obstruction through plastic ventricular remodeling, which, at least in part, restores cardiac performance and myocardium oxygenation.

Regional Frontal Lobe Response Magnitudes During Affective Shifting Covary With Resting Heart Rate Variability in Healthy Volunteers

2016 ◽  
Vol 30 (4) ◽  
pp. 165-174 ◽  
Author(s):  
Ryan Smith ◽  
John J.B. Allen ◽  
Julian F. Thayer ◽  
Richard D. Lane
Keyword(s):  
Heart Rate ◽  
Heart Rate Variability ◽  
Healthy Subjects ◽  
Emotional Reactivity ◽  
Bold Signal ◽  
Resting Heart Rate ◽  
Functional Magnetic Resonance ◽  
Absolute Value ◽  
Cardiac Vagal Control ◽  
Resting Heart Rate Variability

Abstract. We hypothesized that in healthy subjects differences in resting heart rate variability (rHRV) would be associated with differences in emotional reactivity within the medial visceromotor network (MVN). We also probed whether this MVN-rHRV relationship was diminished in depression. Eleven healthy adults and nine depressed subjects performed the emotional counting stroop task in alternating blocks of emotion and neutral words during functional magnetic resonance imaging (fMRI). The correlation between rHRV outside the scanner and BOLD signal reactivity (absolute value of change between adjacent blocks in the BOLD signal) was examined in specific MVN regions. Significant negative correlations were observed between rHRV and average BOLD shift magnitude (BSM) in several MVN regions in healthy subjects but not depressed subjects. This preliminary report provides novel evidence relating emotional reactivity in MVN regions to rHRV. It also provides preliminary suggestive evidence that depression may involve reduced interaction between the MVN and cardiac vagal control.

Resting Heart Rate and Right Frontal Lobe Functioning in Trauma Survivors

2008 ◽  
Author(s):  
Christopher Immel ◽  
James Hadder ◽  
Michael Knepp ◽  
Chad Stephens ◽  
Ryoichi Noguchi ◽  
...  
Keyword(s):  
Heart Rate ◽  
Frontal Lobe ◽  
Trauma Survivors ◽  
Resting Heart Rate ◽  
Frontal Lobe Functioning
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