Does chorionic gonadotropin hormone have a direct action on uterine contractions?

Direct effect of chorionic gonadotropin hormone on uterine contraction in non pregnant and pregnant rats in early and late pregnancy was investigated in the present work. Isolated uteri suspended in organ bath containing Kreb's solution of PH 7.4 at 37C bubbled with carbogen were used. Spontaneous uterine contractions were recorded using isotonic transducer and an ossilograph. It was observed that CG inhibited the amplitude and frequency of uterine contractions. The mechanism of action was investigated. It was found that CG was not acting by increasing cAMP or cGmp or by decreasing calcium influx through voltage operated calcium channels or by decreasing calcium release from the internal myometrial store. But, CG may act by decreasing calcium influx through receptor operated calcium channels and by modulation of prostaglandins synthesis. Thus, CG can be considered one of the hormones which maintain uterine quiescence during pregnancy by direct action

Role of endogenous prostaglandins in excitation contraction of skeletal muscle in rats

Prostaglandins are present in every mammalian tissue. Inhibition of their synthesis by piroxicam was used as a tool to study the role of endogenous PGs in nerve excitability, neuromuscular transmission and direct muscle contraction using isolated gastrocnemius-sciatic preparations from albino rats. It was observed that inhibition of PGs synthesis by piroxicam inhibited directly as well as and to a greater extent indirectly evoked muscle contractions. It decreased peak tetanic tension and produced tetanic fade. Its inhibitory effect on indirect muscle contraction was not reversed by prostigmine. Piroxicam inhibited also acetyl choline-induced-and caffeine induced contractures. But, there was no significant effect on rheobase, utilization time and chronaxia of sciatic nerve by inhibition of PGs synthesis

Role of nitric oxide in cardiac contractility

The aim of the present work was to investigate the direct role of NO, and the possibility that cGMP was its second messenger in cardiac contractility under basal cholinergic and adrenergic stimulated conditions. Experiments were performed on spontaneously beating atrial and electrically stimulated ventricular preparations isolated from rabbits. The results showed that inhibition of NO synthase by nitro-L-arginine had no significant effect on basal atrial or ventricular contractions and that the inotropic effect of acetyl choline or adrenaline did not differ significantly after inhibition of NO synthase. Also, it was observed that L-arginine and sodium nitroprusside decreased significantly ventricular contractions, but atrial contractions were not affected by L-arginine although increased significantly by high concentration of sodium nitroprusside. These effects of L-arginine or sodium nitroprusside were antagonized by the guanylate cyclase inhibitor methylene blue

Effects of proton pump inhibitors and histamine H2 receptor antagonists on gastrointestinal motility

Isolated segments from the different parts of the gastrointestinal tract of rabbit were used. They were suspended in organ bath containing physiological solution of PH7.4 at 37C and bubbled with air. Motility was recorded using isotonic transducter and an ossilograph. The effects of the proton pump inhibitor Omeprazole [5 UM] and the histamine H2 receptor antagonist Ranitidine [3 x 10-4 M] were studied. It was observed that Omeprazole decreases esophageal tone, decreases the amplitude of contractions in stomach and duodenum and decreases both bone and amplitude of contractions in the colon. This inhibitory effect of Omeprazole is abolished by either propranolol or phentolamine indicating an adrenergic effect of Omeprazole. The increased tone is a cholinergic effect since it is abolished by atropine. But the increased amplitude of contractions is not affected by atropine and is aboliahed in calcium free solution indicating that this effect of Ranitidine is due to increased calcium influx from the extracellular fluid

Effect of choloroquine on the serum concentrations of glucose and lipids in rats fed on high fat diet

This study is carried out on 35 rats divided into 4 groups. Group I [control]; fed on balanced diet for 4 weeks, group II; fed on high fat-diet for 4 weeks and injected chloroquine I.P 5 mg/kgm 4 times daily in the last 3 days, and group IV; fed on high fat-diet for 4 weeks and injected chloroquine in the last 3 days. At the end of the food regimen, rats were killed and the blood was analyzed for glucose, triglycerides, total cholesterol, HDL-cholesterol and LDL-cholesterol. Chloroquine injection produces no significant changes in the serum level of glucose and lipids in rats fed on balanced diet but, it lowers significantly the elevated serum concentrations of glucose, cholesterol, and LDL-cholesterol in rats fed on high fat-diet

Effect of somatostatin hormone analogue on intestinal motor activity

The effect of somatostatin hormone analogue, octreotide, on intestinal motor activity were studied using isolated segments from ileum and colon of rabbit. They were suspended in organ bath containing Tyrode's solution of PH 7.4 at 37C and bubbled with air. Motility was recorded using isotonic transducer and an ossilograph. It was found that octreotide was not acting by stimulation of either alpha or beta adrenergic receptors or by blocking muscarinic or hiatamine receptors or by increasing cyclic guanosine monophosphate [cGMP]. But octreotide may act by decreasing cyclic adinosine monophosphate [cAMP] and calcium influx from the extracellular fluid. This inhibitory effect of octreotide on colonic motility is one of its beneficial effects in treatment of persistent diarrheas