In this experiment, contractions of the earthworm gut are measured in an organ bath with a force transducer. The effect of neurotransmitters and ionic concentrations on contraction strength and rate will be investigated.
Written by staff of ADInstruments
With acknowledgement to: Dr. Stuart I. Cromarty, Department of Natural Sciences, Assumption College, Worcester, MA, USA.
Smooth muscle is one of three muscle fiber types found in animals. Unlike skeletal and cardiac muscle cells, smooth muscle cells are not striated, and have single nuclei. Smooth muscles are typically under control of the autonomic nervous system, and do not contract voluntarily. Smooth muscle contracts slowly, …show more content…
You should have 10-15 cm of loose thread available after you tie off the gut so that you can attach the gut to the organ bath and force transducer.
4. Using scissors, carefully remove the gut section from the earthworm.
Mounting the gut in the organ bath
1. Tie the posterior end of the earthworm gut to the mounting hook and mount the hook on the ring stand so the gut is in the organ bath. The distal end of the intestine should be 1 cm from the glass hook. Be sure to hold on to the thread on the anterior end.
2. Lower the force transducer on the micropositioner to its lowest position.
3. Tie the thread on the anterior end of the gut (pharynx end) to the force transducer. The gut should be slack.
4. Carefully raise the micropositioner by turning the adjustment knob until the gut is under slight tension. NOTE: Be extremely careful not to overstretch the gut during this step. The gut is very delicate and could tear easily.
5. Make sure the drain stopcock on the organ bath is closed. Fill the organ bath with normal earthworm saline. The gut should now be completely submerged. If the gut is not completely submerged, you may need to re-tie the lower thread to the hook.
Figure 1. The earthworm gut segment mounted in the organ chamber for recording. The ring stand and force transducer are not shown.
Figure 2. Anatomy of the earthworm gut section.