BIOM2011 Group 2 - Report 2 Final full PDF

Preview

Summary

Course Code BIOMCourse Title Integrative Cell & Tissue BiologyCourse Coordinator Bradley LaunikonisDue Date 10/5/Assignment Title Cardiac Function Labratory ReportWord Count xDate Submitted 9/5/Extension applied for Yes / No Revised DateStudent Number Surname First Namesxxxxxxxxxxx X MANINSE...

Description

Course Code

BIOM2011

Course Title

Integrative Cell & Tissue Biology

Course Coordinator

Bradley Launikonis

Due Date

10/5/2021

Assignment Title

Cardiac Function Labratory Report

Word Count

x

Date Submitted

9/5/2021

Extension applied for Yes

/ No

Revised Date

Student Number

Surname

First Name

sxxxxxxxxxxx

X

MAN

within the sino-atrial node commonly termed the pacemaker of the heart, which controls the action potentials and nervous function of the heart(3). Following a fight or flight response, the autonomic nervous system is activated, resulting in the release of neurotransmitters such as noradrenaline and adrenaline(4). These neurotransmitters subsequently bind to β 1/2-adrenergic receptors (β1/2-AR) present on cardiac cells and in other organs including the lung and kidney(5). Adrenaline is the primary agonist for all β-ARs of the G-protein coupled receptor family (GCPR), which are integral in many physiological processes including nervous system functionality (4,6). Binding to GCPR ligands such as adrenaline results in structural changes and coupling with heterotrimeric G-proteins, resulting in the conversion of G-protein-bound GDP to GTP(5). This detachment of the G-protein leaves active Gα and Gβ subunits to mediate downstream nervous signalling which results in increased heart rate and blood flow(5). O’Donnel et al., (1982) conducted a pharmacological study in cane toads which demonstrated the agonistic effects of adrenaline and antagonistic effects of propranolol following binding to β-adrenergic receptors(7). The authors further demonstrated that these drugs may increase the availability of calcium ions within the nervous system(7). The influx of calcium ions in cardiac cells through multiple pathways such as L-type calcium ions channels promotes cardiac depolarisation and subsequently increases the force of cardiac contraction(8,9). Hence, cane toads can be used as an experimental model to characterise the effects of drugs on cardiac conduction, such as heart rate and cardiac contractile force(8,9).

β‐ adrenergic drugs such as adrenaline an agonist and propranolol an antagonist can be used to modulate sympathiometic nervous system responses such as heart rate and the amplitude of cardiac contraction(7). Understanding how these drugs influence heart rate and the force of cardiac contraction can lead to new treatment methods that promote effective cardiac function(7). Objective: This study will investigate the effects of a β1/2-AR-agonist and a non-selective βantagonist, propranolol both individually and in combination on the cardiac function of a toad. Hypothesis: It is hypothesised that adrenaline will increase the heart rate and force of ventricular contraction causing an increase in cardiac output

whereas propranolol and will

decrease the heart rate and correspondingly depress ventricular contraction and cardiac output. Methods: A double-pitched cane toad was dissected along the ventral surface exposing the thoracic cavity for the removal of the sternum tissue. The pericardium was incised with particular care to ensure the vena cava was not damaged. The heart was then raised from the thoracic cavity by the thumb and forefinger. The ventricle of the heart via a bent pin was attached to the transducer. The heart was then enclosed within the thoracic cavity by cotton thread with the bent pin adjusted to keep the heart beating. The Lab Chart software platform recorded atrial and ventricular mechanical events. The contractile force increased from 6 mN to around 8mN. The heart was then connected to a three lead Electrocardiogram (ECG) to measure the movement of cardiac electrical activity. This requires one lead attached to the muscle wall of the ventricle by copper wire for the positive ECG cable. A second cable (earth) attached on the right near the right collar bone and the third cable (negative) attached to the right hind limb. The experiment then employed the following steps

Confidential

Page 3

5/29/2021

1. The force transducer and ECG were employed to measure baseline cardiac events. These results were used as the scientific control to minimise the effect of any other variable. This was repeated 3 times every 20 seconds and applying frog ringer solution before and after the drug application to wash. 2. Propranolol (100 µL)/(1mM) was administered and the effect of this drug on cardiac function was measured for three minutes. This was repeated 3 times every 20 seconds and applying frog ringer solution before and after the drug application to wash. 3. Adrenaline (100 µL)/(1mM) was administered and the effect of this drug on cardiac function was measured for three minutes. This was repeated 3 times every 20 seconds and applying frog ringer solution before and after the drug application to wash. 4. Propranolol and Adrenaline were administered (100 µL each) in combination. The effect of these drugs on cardiac function was measured for three minutes. This was repeated 3 times every 20 seconds and applying frog ringer solution before and after the drug application to wash. Analysis: LabChart

Reader software (AD Instruments,

Bella

Vista,

NSW,

AU

v8.0) was used to record the heart rate in beats per minute (bpm) and contractile force in millinewtons (mN) for all treatment groups. The heart rate was determined by the number of cycles of ventricular contractions in 10 seconds and the value multiplied by six to obtain beats per minute. All data analysis were completed via Prism ™(GraphPad, San Diego, CA, USA v9.0) software to obtain the statistical results from LabChart. A one-way ANOVA with Tukey post-test was utilised for comparing the control values for both contractile force and heart rate. We analysed using one-way ANOVA with Tukey’s multiple comparisons test. Statistical significance was determined as P...