Effect of ICV injection of Ghrelin ‎and morphine on T3 and T4 ‎plasma levels in rat

Previous studies have shown that ghrelin inhibits the activity of Hypothalamus-Pituitary-Thyroid (H-P-T) axis. It is also proved that ghrelin increases the appetite via Agouti Related Protein and neuropeptide Y Pathway, decreases T3 and T4 secretion. Also morphine by effect on Pituitary hormones like TSH decreases T3 and T4 concentrations. Thus, the goal of this study was to determine the influence of the interaction between ghrelin and morphine on thyroid hormones concentration. Twenty one male Wistar rats weighing 200-250 g were randomly divided into 3 groups. The groups received 5 nmol ghrelin, 1µg morphine or 5 nmol ghrelin together with 1µg morphine in third cerebral ventricle in volumes of 3 μl .The blood samples were collected every day. Starting one day before and up to one day after injections. Brain slices were taken to ensure that the place of the canulae was right. The plasma was analysed by Radioimmunoassay technique to determine T3 and T4 concentrations. The results showed that the i.c.v injection of ghrelin and morphine significantly decreased the mean plasma concentrations of thyroid hormones (P<0.05). Co-administration of these two substances in some of groups showed that decrease mean plasma concentrations of thyroid hormones (P<0.05). This study showed that ghrelin and morphine significantly decreased mean plasma concentration of T3 and T4. Co-administration of two substances in some of groups showed that decrease mean plasma concentration of thyroid hormones (p<0.05).