The Injection Effects of Loratadine and Steroid Hormones into Hippocampus on Motor Skill Learning and Balance in the Rats

Background and Aim : Study of the effect of histamine antagonist, showed that the antihistamines have a different effect on balance and locomotor activity. Loratadine is a long acting antihistamine, that is H1 histamine receptor antagonist and used to treat allergies. This new second-generation antihistamine selectively worked on peripheral H1-receptor sites and passes a very little bit of the blood brain barrier. Therefore, this study aimed to investigate the effects of direct injection of Loratadine on hippocampus function and for a wider study, steroid hormones beside the Loratadine were used and their interaction on the balance and motor skill learning, was investigated.Methods : Twenty-five mature wistar rats weighing 250±25g were randomly divided into the 5 following groups (n=5 rats/group): Control, the groups received Loratadine (CLAR), Loratadine plus Estradiol (CLAR+E2)(2μl+1μl), Loratadine plus Progesterone (CLAR+P2) (2μl+1μl) and Loratadine plus Estradiol and Progesterone (CLAR+E2+P4). Before surgery, the rats motion balance and motor skill was examined with the rotarod set. The rotarod test is a performance test based on a rotating rod with forced motor activity being applied, usually by a rodent. Some of the functions of the test include evaluating balance, grip strength and motor coordination of the subjects; especially in testing the effect of experimental drugs. The test measures parameters such as riding time (seconds) or endurance. Animals in the control groups did not receive any drug. Rats in the drug groups were anesthetized with intra-peritoneal injection and bilateral cannulas were implanted 0.2 mm above hippocampus, by stereotaxic apparatus. A week after the surgery, the drugs were injected into the groups through cannulas. To check the learning and memory criteria, at the end of injection, balance and motor skill learning were assessed by rotarod test again (1,3 and 24 hours after the injection). One-way analyses of variance (ANOVA) followed by Tukey’s post hoc test, were used for analysis of the data.Results : The collected information from pharmaceuticals showed that intra-hippocampus administration injection of Loratadine, significantly (p<0.001) reduced rotarod test. Also, 3 and 24h after the injection of Loratadine plus Progesterone, the results of the rotarod test in this group are significantly(p<0.01) higher than CLAR+E2+P4. and Loratadine plus E2 (CLAR+E2) drug groups. The comparison of the rotarod test of each group suggests that the motor balance index in the control group has significantly(p<0.01) increased in the 3 and 24 hours after injection. The rotarod test of drug groups with respect to the pre - injection drug rotarod test showed a significant decrease at the level (p<0.001). Conclusion : It seems that the injection of Loratadine in hippocampus can decrease motor skill learning and balance. There is an interaction between Loratadine and progesterone hormone in the balance and motion learning at the hippocampus. However, the use of estrogen hormone with Loratadine has no noticeable effect on motion learning and balance.

Keywords:

Loratadine , Steroid Hormones , Memory , Rotarod , Balance , Motion Skill Learning