M. COSTESCU*, H. PĂUNESCU*^#, B.S. VELESCU**, A. ZUGRAVU*, OANA ANDREIA COMAN*, I. FULGA*

* Department of Pharmacology and Pharmacotherapy, “Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania
** Department of Pharmacology and Clinical Pharmacy, Faculty of Pharmacy,”Carol Davila” University of Medicine and Pharmacy, Bucharest, Romania

The actual research was conducted to assess the influences of pretreatment with different doses of serotonin on gastrointestinal motility (rat jejunum) induced by acetylcholine after the depletion of endogenous serotonin by para-chlorophenylalanine in order to evaluate the effect of increased serotonin. Rats of which jejunum was removed, were pre-treated with 300 mg/kg bw para-chlorophenylalanine, for 3 days. The assessments were done using an isolated organ bath with isometric transducers, using Tyrode solution, aerated with air, 37 °C. Different acetylcholine and serotonin doses were added to the bath in order to obtain concentrations of 10^–8 M, 10^–7 M, 10^–6 M, 10^–5 M and 10^–4 M, respectively. Subsequently after one dose of serotonin of  10^–8 M, increasing doses of acetylcholine were added in order to obtain bath concentrations in the same concentration mentioned above. The cycle was repeated with serotonin 10^–7 M, 10^–6 M, 10^–5 M and 10^–4 M. The contractile force, the rate of contractile force development during contraction, the rate of contractile force development during relaxation were assessed. Results were interpreted by calculating the mean and standard deviation for each pair of concentrations. In the present experimental conditions, a complex interaction between serotonin and acetylcholine on intestinal motility was shown

Corresponding author’s e-mail: phpaunescu@yahoo.com

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