The effects of propolis extract on age-associated cognitive deficits in rats
Özet
Background: Propolis is widely used as alternative medicinal product due to their antimicrobial, antiinflammatory and antioxidant properties. Previous studies have shown that propolis has a neuroprotective effect and alleviates the cognitive impairments in scopolamine or beta-amyloid induced learning and memory impairment animal models [1,2]. The incidence of the physiological aging associated neurodegenerative diseases characterized by memory loss and dementia is increasing. The aim of this study is to evaluate the effect of chronic propolis administration on cognitive dysfunctions following physiological aging processes.
Methods: In this study, male Wistar rats were divided into 4 groups (n=10 for each group): young-control (YC-6 months), young-propolis (YP-6 months), old-control (OC-24 months), old-propolis(OP-24 months). The water-soluble form of propolis will be prepared from fresh Turkish propolis (Aksuvital Natural Products Company). The main components in this extract will be identified by Gas Cromathography-Mass Spectrometry (GC-MS) analysis. The extract of propolis (100 mg/kg) was administered orally for 28 consecutive days to YP and OP groups. At the end of 28 days period, locomotor activities, passive avoidance and elevated plus maze tests were performed respectively. In passive avoidance apparatus, which measures emotional memory, acquisition (on day 1), and retention (on day 2) trials were carried out. In acquisition trial, an electric foot-shock was delivered to the animal via grid floor. The time taken for animals to enter the dark compartment was recorded as the training latency. Retention latency was evaluated 24-h after acquisition trial. In EPM test, which measures spatial memory, acquisition (on day 1) and retention (on day 2) sessions were performed. Transfer latency (the time in which the animal moves from the open arm to the enclosed arm) was utilized as an index of learning and memory processes. The rats were placed into the open arm and the transfer latency was recorded for both days. The results of the study were evaluated by one way ANOVA post hoc Tukey test. The data were considered to be significant statistically if the probability had a value of 0.05 or less.
Results: There is no statistically significant differences between the first day transfer latencies in all groups in passive avoidance and elevated plus maze tests. The retention latencies in passive avoidance test significantly reduced in physiologically aged, OC group compared to the YC group (p<0.05). Also, the second day transfer latencies in elevated plus maze test increased in OC group compared to the young controls (p<0.05). The results of both behavioral tests shown the development of cognitive dysfunction because of the physiological aging. After chronic propolis administration, both latencies in OP group reversed to the young control levels.
Conclusion: The results of the study have shown that the chronic propolis extract administration may prevent the emotional and spatial memory impairment during physiological aging. Hence the propolis extract could be considered as a new strategy to prevent or slow down the development of cognitive dysfunctions following physiological aging processes. However, further studies are needed to explore the biological mechanisms of propolis and to support these findings.
