Vol.:(0123456789) 1 3 Anatomical Science International https://doi.org/10.1007/s12565-020-00538-y ORIGINAL ARTICLE Neuroprotective efect of regular swimming exercise on calretinin‑positive striatal neurons of Parkinsonian rats H. Boracı 1  · Ö. Kirazlı 1  · R. Gülhan 2  · D. Yıldız Sercan 1  · Ü. S. Şehirli 1 Received: 15 September 2019 / Accepted: 8 March 2020 © Japanese Association of Anatomists 2020 Abstract In Parkinson’s disease (PD), physical therapy is one of the mainstays of supportive treatment modalities. This study focused on the neuroprotective efect of regular exercise on striatal calretinin positive interneurons in a rat model of PD. 6-hydroxy- dopamine (6-OHDA) was injected unilaterally into the medial forebrain bundle of Wistar rats. 6-OHDA lesioned (Parkin- sonian) and unlesioned (control) rats were divided into sedentary and exercise groups. Exercise groups had daily swimming sessions for 30 min for 6 weeks. After 6-OHDA injections, an apomorphine-induced rotation test was performed (0.05 mg/ kg, subcutaneous) at the 3rd and 6th weeks. At the end of the 6th week, brains were removed following transcardiac perfu- sion. The brain sections were stained immunohistochemically for tyrosine hydroxylase and calretinin reactivity. The num- ber of rotations was signifcantly lower in Parkinsonian exercise group compared to Parkinsonian sedentary group at the 6th week (p = 0.024) and there was signifcant diference between Parkisonian sedentary groups at the 3rd and 6th weeks (p < 0.002). The calretinin positive interneurons signifcantly increased in the Parkinsonian exercise group compared to Parkinsonian sedentary group (p = 0.0003) and control exercise group (p < 0.0001). To conclude, the swimming exercise led to a striking increment of calretinin positive interneurons in the striatum of Parkinsonian rat. These fndings indicated that the neuroprotective mechanism of exercise increased the number of striatal calretinin positive interneurons that might generate new approaches for the mechanism of neuroprotection. We concluded that striatal calretinin positive interneurons have an important role in the neuroprotective mechanisms of exercise in PD. Keywords Calretinin · Parkinson’s disease · Rat · Striatum · Swimming exercise Introduction Parkinson’s disease (PD) is a neurodegenerative movement disorder. The approaches for the treatment focused on the symptoms due to the fact that there is no cure for the dis- ease (Balestrino and Schapira 2020). A variety of treatment modalities are being in use, including drug therapy, deep brain stimulation and supportive treatments. The physical exercise is the clinically approved component of these sup- portive treatments. The efcacy of physical exercise, espe- cially on motor functions, is variable and based upon the frequency, intensity, time and type of exercise (Ammann et al. 2014). By demonstrating an improved physical capacity and increased oxidative capacity of the major muscle groups with no sign of stress, swimming exercise is accepted as a well-liked treatment of PD among experiments in recent years (Haobam et al. 2005; Contarteze et al. 2008). The swimming is a natural ability of rats, and therefore, it is also preferred in experimental rat models (Souza et al. 2009). Several studies in PD animal models claim neuropro- tective efects of exercise on dopaminergic neurons and increase in neurotrophic factors (Garza et al. 2004; Nee- per et al. 1995; Gomez-Pinilla et al. 1998). It is mentioned that treadmill exercise increases cell proliferation as well as receptors for neurotrophic factors BDNF (brain derived neurotrophic factor) and GDNF (glial cell line-derived neurotrophic factor) in the striatum after brain damage (Yi et al. 2009). Both vigorous and voluntary exercises lead to an increase in neurotrophic factors. These neurotrophic * Ü. S. Şehirli usehirli@marmara.edu.tr 1 Department of Anatomy, School of Medicine, Marmara University, Başıbüyük Yolu No: 9/2 Başıbüyük, Maltepe, Istanbul, Turkey 2 Department of Medical Pharmacology, School of Medicine, Marmara University, Istanbul, Turkey