Autonomic Control of Smooth Muscle (Ex. 12)

Procedure:

You will receive a 3 cm long segment of rabbit duodenum in lab today. You will get instructions on how to place the duodenum segment in the Tyrode’s solution warm tissue bath and how to attach it to your balanced (but not calibrated) F-60 myograph. You will then increase the sensitivity until 2-3 cm of pen deflection are observed each time the muscle contracts. Before you begin recording adjust the level of Tyrodes solution in the chamber so that the tissue is immediate below the surface, but not touching the surface. This will allow drugs to diffuse through as little liquid as possible before hitting the tissue surface. Don’t forget to hit the event marker when you add a drug to the tissue chamber. The drugs must be washed out of the chamber after each experiment. You will be instructed on how to do this. Washing also causes the tissue to stop contracting momentarily. You will have to monitor the contraction activity until the tissue returns to normal before going to the next experiment.

Transducer: F-60

Paper Speed: .25 cm/sec

Timer: 10 sec

Stimulus: Chemical

Drug administered:

Drug dosage:

Methods: Record 30 seconds of activity once the tissue has recovered from handling.

Label: measure rate (contractions per minute) and force (Average Centimeters of pen deflection) for the 30 sec control period.

Effect of Epinephrine on Duodenal Activity

Methods: Record 30 seconds of activity then add 1 ml of Epinephrine (5 ug/ml) to the tissue bath, keep recording until the rate and/or force of contractions change then record an additional 30 seconds. Stop the record and wash 4 times.

Label: measure rate (contractions per minute) and force (Average Centimeters of pen deflection) for the 30 sec control period and during the 30 seconds of record when epinephrine is in effect.

Methods: Record 30 seconds of activity then add .5 ml of acetylcholine (1 ug/ml) to the tissue bath, keep recording until the rate and/or force of contractions change then record an additional 30 seconds. Stop the record and wash 4 times.

Label: measure rate (contractions per minute) and force (Average Centimeters of pen deflection) for the 30 sec control period and during the 30 seconds of record when acetylcholine is in effect.

Methods: Record 30 seconds of activity then add .5 ml of physostigmine (50 ug/ml) to the tissue bath, keep recording until the rate and/or force of contractions change then record an additional 20 seconds, now add .5 ml of acetylcholine (1 ug/ml) to the tissue bath, keep recording until the rate and/or force of contractions change then record an additional 20 seconds. Stop the record and wash 4 times. If at any time during this record the tissue stops contracting stop and wash the chamber out.

Label: measure rate (contractions per minute) and force (Average Centimeters of pen deflection) for the 30 sec control period and during the 20 seconds of record when physostigmine is in effect, and during the 20 sec. of physostigmine plus acetylcholine.

Methods: Record 30 seconds of activity then add .5 ml of atropine (200 ug/ml) to the tissue bath, keep recording until the rate and/or force of contractions change then record an additional 20 seconds, now add .5 ml of acetylcholine (1 ug/ml) to the tissue bath, keep recording until the rate and/or force of contractions change then record an additional 20 seconds. Stop the record. If the tissue is still contracting do not wash before going on to the next experiment (or it may not start contracting again). If it stops contracting during this experiment wash the chamber and wait for the activity to increase.

Effect of Sodium Azide (mimics anoxia)

Methods: Record 30 seconds of activity then add 1 ml of sodium azide (650 mg/ml) to the tissue bath, keep recording until the rate and/or force of contractions are almost completely diminished.