Additive effects of propofol and midazolam on dopamine vasodilatation of isolated rabbit renal arteries

Background and objective

This study evaluated the effects of varying doses of propofol and midazolam on the vasodilatation due to low-dose dopamine in an isolated rabbit artery model.

Methods

Twenty-four New Zealand rabbits (2–2.5 kg) were used in the study. All of their left renal arteries were extracted. Renal artery strips 2–3 mm in length were mounted in 20 ml organ baths containing Krebs-Henseleit solution. In order to determine the maximal concentration for dilating the artery tissue, dopamine was added in cumulative log concentrations (10^-9–10^-5 M) to the bath after the tissue had been contracted with the KCl solution. The concentration that had the maximal relaxation effect was the one used in the subsequent trials of propofol and midazolam. After contraction with KCl solution and then relaxation with low-dose dopamine, tissue preparations were exposed to either cumulative log concentrations (10^-9–10^-5 M) of propofol (n = 8) or midazolam (n = 10). The force on the transducer was then recorded, and these measurements were translated into percentages of the initial contraction force.

Results

Dopamine-induced relaxation (3 × 10^-7 M) of the renal artery preparation was increased to a similar extent with the addition of midazolam at all concentrations (10^-9–10^-5 M). Propofol caused a concentration-dependent increase in relaxation (P < 0.05). Midazolam concentrations greater than 10^-9 M (10^-8–10^-5 M) resulted in a significant increase in relaxation of the artery tissues (P < 0.05). The amount of relaxation in the propofol and midazolam groups was not significantly different (P > 0.05).

Conclusions

In this rabbit renal artery dilatation model using dopamine, the addition of either propofol or midazolam results in a statistically significant increase in the vasodilatatory effect of dopamine.