Course Code BIOM2011

Course Code BIOM2011 Course Title Integrative Cell and Tissue Biology Course Coordinator Associate Professor Bradley Launikonis Due Date 10/05/2022 Assignment Title Effects of Experimental Drug Agents on Cardiac Function Word Count 1643 Date Submitted 11/05/2022 Extension applied for Yes / No Revised Date -

Student Number SurnameFirst Name 46500937AroraSiddhant This study source was downloaded by 100000864769797 from CourseHero.com on 08-31-2023 07:48:39 GMT -05:00 https://www.coursehero.com/file/199512014/Cardiac-Prac-Report-Submission-Siddhant-Aroradocx/

Introduction The sympathetic nervous system plays an integral role in stress-induced cardiac activity, first garnered and expressed by Walter Branford Cannon in his literature titled "Fight or Flight" Response (Craft, J et al., 2019). The sympathetic response is monitored across numerous species, with primary reference made to cane toad species (Bufo marinus) in this report. Regarded for its administered positive chronotropic and inotropic effects, inducing the sympathetic response triggers multiple physiological adaptations, including but not limited to; accelerated heart rate (HR), increased ventricular contractile force (VCF) and cardiac contractility (Lakkatta EG, 2004).Following inducement of the flight or flight response, activation of the autonomic nervous system (ANS) is initiated, releasing specific neurotransmitters, noradrenaline and adrenaline (O’Donnel SR; Wanstall JC, 1982). Part of the triggered response via the ANS is the subsequent binding process by which the neurotransmitters bind to β1 and 2-adrenergic receptors (β1/2-AR) present on cardiac cells (Madamanchi A, 2007). A variety of physiological processes, including nervous system functionality, is regulated by the hormone adrenaline, a primary agonist of all β-ARs within the G-protein coupled receptor family (GCPR) (Pavoine C; Defer N, 2005). Adrenaline binds specifically to GCPR-ligands and induces structural changes in the G-protein by coupling to heterotrimeric G-proteins, facilitating the conversion of G-protein-bound GDP to GTP (Madamanchi A, 2007).Undergoing detachment of the G-protein leaves active Gα and Gβ subunits to mediate downstream nervous signalling and action potential propagation, yielding an increase in blood flow and HR (Madamanchi A, 2007).A representation of the effects of adrenaline is thoroughly catalogued in the pharmacological study conducted by O'Donnel et al. (1982) in cane toads, which distinctively demonstrated the antagonistic effects of propanol and agonistic effects of adrenaline subsequent to binding with β-adrenergic receptors. The author's findings further observed a correlation between drug administration and an influx in the availability of calcium ions within the nervous system (O'Donnel et al., 1982). This increased availability of calcium ions infused into cardiac cells through multiple pathways, specifically L-type channels, facilitates cardiac depolarisation, coupled with a subsequent increase in VCF (De Ruijter W et al., 2002). This study, coupled with substantial evidence from other sources, suggests that cane toads are a viable experimental option applicable when accurately characterising the effects of drugs on cardiac conduction, specifically HR and VCF (De Ruijter W et al., 2002). This study source was downloaded by 100000864769797 from CourseHero.com on 08-31-2023 07:48:39 GMT -05:00 https://www.coursehero.com/file/199512014/Cardiac-Prac-Report-Submission-Siddhant-Aroradocx/

The β-adrenergic drugs can be employed to modulate sympathomimetic nervous system activity effectively, particularly its responses to physiological shifts, catalysing modifications in HR and VCF (O'Donnel et al., 1982). Thorough research and critical analysis of findings concerning drug-induced changes can provide a gateway to developing new treatment methods responsible for promoting and facilitating adequate cardiac function (O'Donnel et al., 1982). With selective application of the aforementioned scientific literature, this study will investigate the effects of β1/2-AR-agonist through adrenaline and propranolol as the non-selective β- antagonist, with individual and combined observance of the effects on cardiac function in the Bufo marinus species. Hypothetically, it is anticipated that a direct correlation will exist between increasing adrenaline stimulation and increasing HR and VCF in the Bufo marinus species. On the contrary, propanol administration is expected to have an inverse effect generating reductions in HR and VCF with increasing propanol.

Method:

A double-pithed Bufo marinus was used to experiment. The double-pithed toad was placed on its ventral side up on the dissection mat, pinned down in a supine arrangement.Using forceps, longitudinal and lateral incisions were made along the Bufo Marinus' ventral surface, exposing the thoracic cavity. Subsequently, the pericardium lining the heart was pierced, revealing the heart.With considerable care, the heart was gradually elevated from the thoracic cavity and hooked to a force transducer by threading a needle through the apex of the Bufo Marinus' heart. This allowed one end of the threading to elevate the heart and the other end to be incorporated onto a small hook concatenating the force transducer. The thread aligning the elevated heart and the force transducer was adjusted for sufficient tension (taut) to a degree varying between 5.5 to 7mN. Earth, positive and negative electrocardiogram (ECG) leads were attached to the respective limbs on the Bufo Marinus sample, two on the legs and one on the left forearm. Room temperature Ringer's solution was periodically applied to the experimental sample to maintain adequate tissue function.To investigate the effect of the experimental condition, Lab Chart was utilised to accumulate all baseline and experimental data, i.e. HR and VCF. This baseline data was utilised as the scientific control to ensure the minimisation of any effects from other variables. This study source was downloaded by 100000864769797 from CourseHero.com on 08-31-2023 07:48:39 GMT -05:00 https://www.coursehero.com/file/199512014/Cardiac-Prac-Report-Submission-Siddhant-Aroradocx/

When testing the experimental drug agents, propanol (100 µL)/(1mM) was initially administered with the subsequent applied effect observed and measured for 3 minutes. Three replicates were conducted following a period of 20 seconds. After obtaining data for propanol, adrenaline was administered to the Bufo marinus sample with the subsequent applied effect observed and measured for 3 minutes. Finally, both experimental drug agents were applied in tandem with the subsequent applied effect on cardiac function observed and measured for 3 minutes. Ringer's solution was periodically applied to the experimental sample to maintain adequate tissue function before and after drug administration per replicate.LabChart Reader software by AD instruments was utilised to record all data with experimental conditions, HR recorded in beats per minute (bpm) and VCF recorded in millinewtons (mN) across all treatment groups/replicates. In order to calculate bpm, the number of ventricular contraction cycles in the heart every 10 seconds was multiplied by six.All raw data was inputted into and analysed using GraphPad Prism. The software was employed as it can efficiently generate statistical results from data. To generate a comparison amongst the scientific control and treatment groups, a one-way ANOVA with Tukey post-test was employed when generating statistical results for both HR and VCF. Analysis was done using one-way ANOVA utilised in conjunction with Tukey's multiple comparison test to allow for inference of comparative inferences across all treatments. Statistical significance was determined to be P<0.05 amongst all experimental groups. This study source was downloaded by 100000864769797 from CourseHero.com on 08-31-2023 07:48:39 GMT -05:00 https://www.coursehero.com/file/199512014/Cardiac-Prac-Report-Submission-Siddhant-Aroradocx/