Effect of 6-OHDA growth hormone on the calcium binding proteins located in the bulbus olfactorius in Parkinson model rats

Abstract

Objective: Parkinson's disease is the second most common neurodegenerative disease. One of the earliest signs is hyposmia which may appear in the premotor period resulting from the alpha-synucleinopathy that affects the neurons along the olfactory pathway. Growth hormone (GH) stimulates cell growth and regeneration. The recovery of neuronal functions may be correlated with the GHs. Calretinin can buffer calcium when intracellular calcium levels increase. This study aims to investigate the effect of GH on calretininpositive neurons in the olfactory bulb of Parkinsonian rats. Materials and Methods: 6-hydroxydopamine (6-OHDA) was injected intracranially. GH (0.15 mg/kg/day) and saline were administered subcutaneously for treatment and control groups respectively. Calretinin staining was performed on the sections and calretininpositive neurons in the lateral olfactory tract were counted. Results: Thickness of the lateral olfactory tract was lesser in the control group. The decrease in the thickness of the tract may be an important sign of hyposmia. The calretinin-positive neurons in the olfactory bulb of the treatment group are more in number when compared with the control group. Conclusion: The decrease in expression of calcium-binding proteins is closely related to neurodegenerative diseases. As a result, the slight increase compared to the control group may be due to the neuroprotective effect of GH.