The effect of local anesthetics on the transmural potential difference of the small intestine of the rat

Abstract

It has been postulated that intestinal transmural potential difference (PD) depends on active transport of Na⁺ and glucose. Since local anesthetics are known to interfere with Na⁺ and K⁺ movement through nerve and red cell membranes, the effect of local anesthetics on PD was investigated. An apparatus for in vitro study of transmural PD and absorption in the small intestine of rats was described. In this system the isolated gut was found to remain viable for at least 90 min. Dibucaine HCl (0.04%) and tetracaine HCl (0.15%) depressed the negative polarity of the mucosal surface. Procaine (1.0%) depressed further and finally reversed the PD to a positive polarity. In the concentration used, procaine increased the osmolarity of the mucosal solution. In the control preparation a similar increase in osmolarity, achieved by the addition of mannitol, also resulted in a fall of PD. It is thought that the total effect produced by procaine was the sum of the osmolar and pharmacological actions of the drug. A possible relationship between Na⁺ and glucose transport in relation to the depressing effect of local anesthetics on the PD was discussed.