Electromyogram of rabbit colon and cecum in vitro.

The rabbit colon is unique in that the proximal colon has taenia coli, but the distal colon has none. Electromyograms were studied from the mucosal and serosal sides of the proximal (taenial) and distal (nontaenial) rabbit colon and cecum. In the proximal colon, similar electromyograms could be obtained from either the mucosal (circular muscle) or serosal (taenia coli) side. Spike bursts occurred in 18.6% of slow waves from the serosal side; however, there were none from the mucosal side. Unlike the proximal colon, the serosal side of the distal colon gave a better electromyographic recording which showed electrical silent periods and variable amplitudes of slow waves. Recordings could also be obtained equally well from both the mucosal and serosal sides of the rabbit cecum. Acetylcholine significantly increased (p less than 0.05) the percentage of slow waves with spikes in taenial colon and the electrical active period in nontaenial colon, whereas atropine, phenylephrine, isoproterenol, and tetrodotoxin produced a significant decrease (p less than 0.05). This study showed that the electromyograms of the rabbit colon and cecum were complex. Although differences existed between the taenial and nontaenial colon, they exhibited similar responses to some autonomic drugs. Furthermore, recordings could be obtained from both sides of the proximal colon and cecum.