Central Injection of Ghrelin Improves Motor Balance in the Rotarod Test in the Rats: Altering the Expression of Drd1 Gene

Abstract

Introduction: Motor learning consolidates in adulthood, and its defects begin to appear with aging. Ghrelin, an endogenous peptide, improves memory and learning, targeting dopaminergic circuits. While cytidine diphosphate choline (citicoline) is known as a common drug for enhancing memory and learning in aging, it is not recommended for adults due to its side effects. The current study aimed at investigating if ghrelin treatment would improve motor learning via the expression of a relevant gene. Methods: For this experimental study, adult male Wistar rats were randomly divided into five groups: control group, three groups of ghrelin treatment (0.3, 1.5, and 3 nmol/μL), and one group with citicoline treatment. The injections were done intra-hippocampally. The motor learning rate was determined using the rotarod performance test by measuring the resistance to falling. Then the expression of dopamine receptor type D1 (Drd1) gene in the hippocampus was measured by a real-time polymerase chain reaction (PCR). Results: Ghrelin (3 nmol/μL) and citicoline had similar and significant effects on motor learning improvement (P<0.01). Both drugs significantly increased Drd1 gene expression (P <0.001). Conclusion: Ghrelin, like citicoline, improves motor learning by altering the expression of Drd1 gene in the hippocampus.