الفهرس 
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Abstract
The present study was performed to investigate some pharmacodynamic effects of spectinomycin. The present study was divided into two types of experiments which were in-vitro and in-vivo experiments. The in-vitro experiments were applied to investigate the effect of spectinomycin on isolated smooth, cardiovascular muscles and neuromuscular preparations. Smooth muscle preparations such as gastrointestinal (guinea pig’s ileum, rabbit’s duodenum, rat’s colon and rat’s fundic strip), rat’s uterus and guinea pig’s tracheal chain. Cardiovascular muscle preparations such as guinea pig’s auricles, rabbit’s heart and rabbit’s aortic strip. Neuromuscular preparations such as frog’s gastrocnemius muscle sciatic nerve, frog’s rectus abdominis muscle and rat’s phrenic nerve hemi diaphragm.
The in-vivo experiments were applied to investigate the effect of spectinomycin on electrocardiograph parameters in conscious rabbits, analgesic activity of spectinomycin in mice and antipyretic effect of spectinomycin in rats. Spectinomycin in concentration lower than 80 μg/ml bath had no effect on guinea pig’s ileum, while 160 to 320 μg/ml bath caused slight inhibition in the force of contraction. Higher concentrations (640 to 1280 μg/ml bath) caused marked inhibition in the force and rate of contractions. Complete relaxation was achieved by addition of 2560 μg of spectinomycin / ml bath.
Concentration of spectinomycin at 40 μg /ml bath had no effect on the duodenal motility of rabbits. Concentrations from 80 to 160 μg/ml
bath caused slight inhibition on the force of contraction. Concentrations from 320 to 640 μg spectinomycin/ml bath induced marked inhibition in the force of contraction of isolated rabbit’s duodenum. Complete relaxation was achieved by a concentration of 1280 μg spectinomycin/ml bath.
Spectinomycin in concentration at 40 μg/ml bath had no effect on the rat’s colon motility. Concentrations from 80 to 160 μg/ml bath spectinomycin caused slight inhibition in the force of contraction. Concentrations of spectinomycin from 320 to 640 μg/ml bath caused marked inhibition in the force and rate of contraction. Complete relaxation was achieved by concentration of 1280 μg/ml bath spectinomycin. The inhibitory effect of spectinomycin on the isolated intestinal smooth muscle preparations appeared to be attributed to its direct effect, which proved by addition of acetylcholine as cholinergic agonist, nicotine sulfate in small concentration as ganglionic stimulant to rabbit’s duodenum, guinea pig’s ileum and rat’s colon caused a marked stimulation in the presence of spectinomycin. Moreover, spectinomycin induced its intestinal relaxant effect even after complete blockage of ά-adrenergic receptors by phentolamine, therefore these results proved that the effect of spectinomycin seemed to be mostly through a direct inhibitory effect on the intestinal smooth muscle i.e myogenic effect. Spectinomycin in concentrations lower than 80 μg/ml bath had no effect on the motility of rat’s fundic strip. spectinomycin in concentration of 160 μg/ml bath caused slight inhibition of the motility of rat’s fundic strip. Spectinomycin in concentrations 320 to 640 μg/ml bath caused marked inhibition of the motility of rat’s fundic strip. Complete relaxation was produced by the concentration of 1280 μg/ml bath. In presence of spectinomycin, histamine was not able to produce its stimulant effect on the rat’s fundic strip, so spectinomycin might appeared to have an antihistaminic like effect.