Abstract
The effects of tetracaine and lidocaine on contractile responses of rat aorta to norepinephrine and KCl were measured and compared to the antagonism of norepinephrine and KCl by N-(2-chloroethyl)dibenzylamine hydrochloride (Dibenamine). Also, the effect of tetracaine on enrbamylcholine-induced contractions of rat trachea was investigated. Analysis of cumulative dose-response curves showed that the local anesthetics antagonized norepinephrine. carbamylcholine and KCl in a manner similar to that seen with Dibenamine. The initial parallel shift to the right of the norepinephrine and carbamycholine dose-response curves produced by the local anesthetics appeared to be caused by a change in the affinity constant of both the adrenergic and cholinergic receptors. The nonparallel shift in the dose-response curves seen with higher concentrations of the local anesthetics and the noncompetitive antagonism of the response to potassium were probably caused by the well-known effects of local anesthetics on the mobilization of Ca++ needed for smooth muscle contraction.
Footnotes
- Received September 22, 1972.
- Accepted March 12, 1973.
- © 1972 by The Williams & Wilkins Co.
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|