DIGITAL ANALYSIS OF THE PHARMACOLOGICAL EFFECTS OF IN-VITRO ISCHEMIA ON RABBIT CORPUS CAVERNOSUM

Purpose: Regulation of corporal smooth muscle tone is essential for th e initiation of penile erection. In recent years, in vitro isometric t ension studies using isolated corpus cavernosal tissue have been used extensively to investigate the mechanisms regulating corporal smooth m uscle tone and tension. In the present study, we utilized digital anal ysis of contractile data generated from investigation of contractile a nd relaxation responses of isolated rabbit corpus cavenosum to various forms of stimulation. Digital analysis of the contractile and relaxat ion data allows quantitation of both maximal and mean rates of tension change, and time elapsed to maximal response. Rates of tension change s may provide additional important information regarding cellular even ts that mediate corporal tone and tension changes. Methods: Sexually m ature male New Zealand White rabbits were used. Each corpus cavernosum was dissected sharply from the removed penis, then two longitudinal s trips were prepared fur isometric tension studies and placed in indivi dual baths. Tension was monitored continually using an 8-channel Grass Polygraph. The Grass PolyVIEW system simultaneously converted analog signals to digital information and stored data using a 486 PC computer . Each corporal strip was prestimulated with 300 mu mol/l phenylephrin e to produce a maximal contraction, then field stimulation (FS), carba chol and nitroprusside were applied consecutively to determine relaxat ion effects. This procedure was repeated after strips were deprived of glucose and oxygen (in vitro ischemia) for 1 h. The following paramet ers were quantitated for all responses: maximal tension change; maxima l and mean rates of tension change, and time to maximal response. Resu lts: Effects of 1-hour in vitro ischemia on rabbit corporal tissue wer e as follows: (If an 85% decrease in contractile response to phenyleph rine, and (2) a marked increase in rate of contractile response to phe nylephrine. Phenylephrine precontracted strips exhibited: (3) no chang e in relaxant response to FS; (4) increased relaxant responses to carb achol and nitroprusside: (5) no change in rates of relaxation in respo nse to FS; (6) increased rates of relaxation in response to carbachol and nitroprusside, (7) no change in elapsed time to maximal relaxation in response to FS, and (8) decreased elapsed time to maximal relaxati on in response to carbachol and nitroprusside. Conclusion: Digital ana lysis of the data generated facilitates recording, reviewing and analy zing of in vitro isometric tension studies on rabbit corpus cavernosum . Digital analysis allows quantification of additional parameters that have important implications for determination of mechanisms by which specific pathological processes occur.