Abstract
OBJECTIVES:In addition to the classic motor symptoms of Parkinson’s disease (PD), patients also present with non-motor symptoms, such as autonomic dysfunction, which is present in almost 90% of patients with PD, affecting the quality of life and mortality. Regarding sex differences in prevalence and presentation, there is increasing concern about how sex affects autonomic dysfunction. However, there are no previous data on autonomic cardiac function in females after 6-hydroxydopamine (6-OHDA) striatal injection.METHODS:Wistar female rats were ovariectomized. After 20 days, the animals received bilateral injections of 6-OHDA (total dose per animal: 48 µg) or a vehicle solution in the striatum. Thirty days after 6-OHDA injection, subcutaneous electrodes were implanted for electrocardiogram (ECG) recording. Ten days after electrode implantation, ECG signals were recorded. Analyses of heart rate variability (HRV) parameters were performed, and the 6-OHDA lesion was confirmed by analyzing the number of tyrosine hydroxylase-positive neurons in the substantia nigra pars compacta (SNpc).RESULTS:A high dose of 6-OHDA did not affect HRV of females, independent of ovariectomy. As expected, ovariectomy did not affect HRV or lesions in the SNpc after 6-OHDA injection.CONCLUSIONS:We suggest that females with 6-OHDA present with cardioprotection, independent of ovarian hormones, which could be related to female vagal predominance.
Highlights
Parkinson’s disease (PD) is a neurodegenerative disease that affects 1% of the general population and 3% of the population over 60 years of age [1]
Tyrosine hydroxylase (TH) Immunohistochemistry To analyze the effect of the injection of 6-OHDA or saline into the CPu, the number of TH+ neurons in the substantia nigra pars compacta (SNpc) was analyzed (Figures 1A–B)
Ovariectomy had no effect on the number of TH+ neurons in the SNpc in any of the five levels analyzed, and the analysis did not show an interaction between ovariectomy and 6-OHDA injection
Summary
Parkinson’s disease (PD) is a neurodegenerative disease that affects 1% of the general population and 3% of the population over 60 years of age [1]. This prevalence is expected to double in the few decades due to demographic aging [2]. PD is classically characterized by motor clinical manifestations caused by the loss of dopaminergic neurons in the nigrostriatal pathway. PD patients present with non-motor symptoms that could precede motor dysfunction by up to 10 years [3]. Non-motor symptoms are related to autonomic function, which affects up to 90% of patients [4].
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