Real-Time Detection of Ferulic Acid Effects on Rat Left Ventricle Using Pressure-Volume Conductivity Catheter

This protocol describes a method for measuring left ventricular pressure and volume using the pressure-volume conductance technique. This method enables continuous real-time monitoring of the effects of drugs on the heart.

Anesthesia is an unavoidable issue in animal experiments. In this experiment, the different levels of anesthesia have a significant impact on the experimental results. This pressure-volume loop measurement method is easier to learn compared to the open-chest method, including fewer experimental tools and less learning time for experimenters.

Our lab will research traditional Chinese medicine's effects and mechanisms on cardiovascular diseases, exploring its extensive but not fully understood impact on heart health. To begin, immerse the pressure-volume sensor of the conduction catheter instrument into 0.9%sodium chloride solution. Once the sensor has been saturated, connect the experimental setup.

Press the Start icon on the software to automatically record the monitoring data from the pressure-volume sensor. Next, calibrate the pressure and conductivity with the Mikro-Tip pressure-volume software. Immobilize the anesthetized rats on an isothermal heating plate, keeping the back in contact with the plate.

Coat a temperature probe with petroleum jelly and insert the probe into the rectum of the rat. Now, make a four-centimeter long incision on the right side of the median line on the rat's neck. Use forceps to separate the muscle and connective tissue.

Isolate the carotid artery from the other tissues. Then place three 5-0 surgical lines below the carotid artery. Drip sterile 0.9%sodium chloride solution onto the artery to keep it moist.

Now, cut the skin above the left clavicle and peel off the tissue around the jugular vein. Cross the left jugular vein with a 5-0 surgical line. Then ligate the distal end of the right carotid artery.

Clamp the arterial clips proximally to suspend the blood flow. With micro scissors, cut a section in the vessel where the blood flow has stopped. Insert a catheter along the carotid artery deep into the left ventricle.

Ensure that the lowest systolic pressure after ventricle entry is close to zero millimeters of mercury. Slightly adjust the pressure-volume catheter to obtain a reasonable pressure-volume relationship. Ligate the proximal end of the surgical line to prevent massive blood loss and change in catheter position.

When the pressure-volume stabilizes, ligate the surgical line distal to the ligated jugular vein. Slowly inject up to one milliliter per kilogram of ferulic acid. Now, inject 50 microliters of 20%sodium chloride solution from the left jugular vein to remove the parallel conductance generated by the myocardium.

Once the testing is complete, use a blood collection needle to withdraw blood from the rat's abdominal aorta. Transfer the collected blood into a sodium heparin collection tube and invert the tube two times to prevent blood clotting. After euthanizing the animal with excess anesthesia, place the collected blood into the orifice of a calibration tube.

The catheter will automatically detect the blood conductance and record it in the monitoring module. A marked increase in pressure was observed as the catheter entered the left ventricle from the carotid artery. The left ventricular pressure was observed to be within 10 to 105 millimeters of mercury, and the conductance volumes were within 65 to 115 microliters.

The complete cardiac cycle was formed by the counterclockwise pressure-volume loop. The administration of ferulic acid induced significant changes in the heart function. The injection of hypertonic saline through the left jugular vein caused an increase in conductivity values.