Smooth Muscle Contraction in Rabbit Intestine

Study Notes

Smooth muscle contraction occurs spontaneously in the rabbit small intestine, meaning it is not dependent on motor or autonomic nerve stimulation.
The smooth muscle is under involuntary control by the endocrine and autonomic nervous systems.
The instability of the smooth muscle membrane potential leads to continuous, irregular contractions in the absence of nerve supply. This is called tonus or tone.
Action potentials spread through gap junctions between smooth muscle cells, triggering a wave of muscle contraction.

A kymograph is a device that records physiological variables.
It is a revolving drum with paper wrapped around it, onto which a stylus moves to record changes in variables like motion.

To study the autonomic properties of smooth muscle in the rabbit small intestine in response to various agents.

The rabbit should be sacrificed humanely using cervical dislocation, without using anesthetic.
The abdomen is cut open and the jejunum is located and cut into 1-inch pieces.
These pieces are kept in a Petri dish containing Tyrode's solution.
One end of the jejunum is attached to a hook in the muscle chamber.
The chamber is filled with 100 ml of warm Tyrode's solution and aerated with a 95% oxygen / 5% carbon dioxide mixture.

Jejunum segments shorten when placed in cold solution, and motility ceases.
Motility returns within 5-10 minutes when the segments are placed in warm (37°C) Tyrode's solution within the muscle bath.
Adding drugs directly to the bath allows for rapid changes in muscle tonus to be recorded.
It is recommended to replace the solution between drug additions to allow for a 1-2 minute stabilization period after replacement.