Comparative Effects of Tramadol on Vascular Reactivity in Normotensive and Spontaneously Hypertensive Rats

Abstract

The aim of the present study was to determine the effects of tramadol on vascular reactivity in aortic rings from Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). Aortic rings, with or without endothelium, were obtained from male WKY rats and SHR (15-20 weeks old) and prepared for isometric tension recording. Aortic rings were precontracted with phenylephrine (10 micromol/L) or 40 mmol/L KCl and then exposed to cumulative concentrations of tramadol (0.1-1 mmol/L). Tramadol produced a concentration-dependent relaxation of precontracted aortic rings from WKY rats and SHR, which was not dependent on functional endothelium. Vascular relaxation was significantly greater in rings from SHR than WKY rats. The concentration of tramadol necessary to produce a 50% reduction of the maximal contraction to phenylephrine (IC(50)) in rings with and without endothelium from SHR was 0.47 +/- 0.08 and 0.44 +/- 0.03 mmol/L, respectively (P = 0.76). Tramadol attenuated the contracture elicited by Ca2+ in depolarized tissue, suggesting that it may inhibit L-type Ca2+ channels. However, pretreatment with nicardipine (1 micromol/L) prevented the relaxation induced by tramadol in aortic rings from WKY rats and partially reduced its inhibitory effect in aortic rings from SHR. 6. Pretreatment of endothelium-denuded aorta with glybenclamide (3 micromol/L), 4-aminopyridine (3 mmol/L), tetraethylammonium (3 mmol/L) and naloxone (100 micromol/L) did not affect tramadol-induced vasodilation of aortic rings from either WKY rats or SHR. Intravenous administration of tramadol (10 mg/kg) to conscious SHR significantly reduced both systolic and diastolic blood pressure from 171.4 +/- 5.3 to 129.3 +/- 5.3 (P = 0.002) and from 125.0 +/- 6.5 to 57.8 +/- 8.9 mmHg (P = 0.003), respectively.

Vasodilatory activity and antihypertensive profile mediated by inhibition of phosphodiesterase type 1 induced by a novel sulfonamide compound

“…In some experiments, N ‐nitro‐ l ‐arginine methyl ester hydrochloride ( l ‐NAME; 100 μ m ) [17], 1H‐[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ; 10 μ m ) [18], Diphenhydramine hydrochloride (10 μ m ) [19], indomethacin (10 μ m ) [18], naloxone (100 μ m ) [20], atropine (10 μ m ) [21], wortmannin (300 n m ) [22], propranolol (10 μ m ) [23], HOE 140 (1 μ m ) [24], sildenafil (0.1 and 100 μ m ) [25], SQ 22536 (100 μ m ) [17], nicardipine (1 μ m ) [20] were added to the saline solution in chambers 15–30 min before phenylephrine and LASSBio‐985. Results are expressed as the percent relaxation of the maximum contractile tension to phenylephrine after LASSBio‐985 concentrations addition.…”

Tramadol hydrochloride: An alternative to conventional local anaesthetics for intraoral procedures- a preliminary study

“…[11][12][13] It is known to cross the blood brain barrier and has a vasodilating property. 14,15 The plasma protein binding for this drug is approximately 20% 11 and is poorly lipophilic. 16 Tramadol is known for its strong analgesic effect and has been used in dentistry for pain relief since many years.…”