Role of adrenergic receptors in the caffeine-induced increase in glucose uptake by the canine hindlimb

The present study was designed to investigate the effects of alpha and beta adrenergic receptor blockers on caffeine-induced increase in canine hindlimb glucose uptake. The study was carried out on fasted male anaesthetized dogs divided into five groups (5dogs per group). Each dog was given a bolus injection of normal saline, caffeine (6mg/kg) caffeine after pretreatment with prazosin (0.2mg/kg). Caffeine (6mg/kg), caffeine after pretreatment with prazosin (0.2mg/kg), propranolol (0.5mg/kg) or combination of prazosin (0.2mg/kg) and propranolol (0.5mg/kg). The experiments were carried out under resting and exercising conditions of the hindlimb. Hindlimb glucose uptake (HGU) was calculated as the product of blood flow and arterio-venous glucose difference. Blood glucose was determined by the glucose oxidase method and blood flow to the hindlimb was determined by time-collection method. The results showed that pretreatment of the animal with either prazosin or propranolol significantly reduced caffeine-induced hyperglycemia, glucose extraction and hindlimb glucose uptake at rest. The two blockers also separately reduced caffeine-induced hyperglycemia during contraction of the hindlimb. Prazosin or propranolol did not however influence the effect of caffeine on glucose extraction and hindlimb glucose uptake during contraction of the hindlimb. It was therefore concluded that alpha and beta adrenergic receptors are involved in caffeine induced responses at rest and not during hindlimb contraction. Key words: Adrenergic receptors, Caffeine, dog, Glucose uptake

Attenuation of impaired uterine contractile activity by ascorbic acid supplementation during early gestational variable stress exposure in Wistar rats

Background: This study investigates the effect of ascorbic acid supplementation during early gestational variable stress exposure on stress markers and in-vitro contractile responses of the uterus. Methods: Twenty nulliparous pregnant rats (180-200 g) were randomly divided into 4 groups of 5 each. Stressed animals were variably exposed to 6 non-habituating and painless stresses (sleep deprivation, predator exposure, immobility, rapid cage changes, noise, and foreign object). Treated groups received ascorbic acid supplementation orally (10 mg/kg bwt) with or without stress exposure while control group received normal saline only. Stress exposure and ascorbic acid treatment was during gestation days (GD) 1-8. Serum cortisol, oxidative biomarkers and in-vitro contractile responses of excised uterine tissue to acetylcholine, oxytocin, calcium chloride, potassium chloride, diclofenac, and magnesium were assessed. Statistical significance was taken at p<0.05. Results: Ascorbic acid supplementation in stressed pregnant group significantly deceased (p < 0.05) MDA activity. Catalase activity was enhanced in ascorbic acid supplemented stressed group while serum cortisol levels were significantly (p < 0.05) reduced in ascorbic acid supplemented stressed group when compared to stress only exposed group. Concentration dependent contraction responses to acetylcholine, oxytocin, calcium chloride, and potassium chloride were significantly reduced in stressed only pregnant rats. Ascorbic acid supplementation in stressed group reversed these reductions. However, doses of diclofenac and magnesium showed no significant effect on relaxation responses across all groups. Conclusion: Ascorbic acid supplementation during early gestational variable stress exposure attenuated impaired contractile functions of the uterus. Enhanced antioxidant enzymes and suppressed MDA activity appear to play a role in the modulation Keywords: Variable stress, early gestation, uterine contractility, ascorbic acid, oxidative stres

Effects of Electrical Vagal Stimulation and Bilateral Vagotomy on Bile Flow and Electrolyte Composition in Rats

Effect of electrical vagal stimulation and bilateral vagotomy on the flow and electrolyte composition of bile was studied in fasted and anaesthetized male albino Wistar Rats. Entero-hepatic circulation was maintained artificially by continuous infusion of 1% sodium teurocholate. In each experiment, bile was collected at 15 mins intervals for a period of 90 mins. The bile aliquot was then analyzed for sodium and bircarbonate. The results showed that vagal stimulation significantly increased bile flow and had no effect on the bile concentration of sodium and bicarbonate. Bilateral vagotomy had no significant effect on bile flow, sodium and bicarbonate concentration. The results of this study suggest a very limited role of the vagus nerves in the secretion of bile in the rat.KEYWORDS: Bile flow, Bile electrolytes, Vagotomy, Electrical stimulation