Caffeine improved spatial learning and memory deficit in sleep deprived female rat

Previous studies have shown that caffeine has beneficial effects on cognitive impairment in sleep deprived male rats. Therefore in the present study, we examined the effects of chronic caffeine administration on learning and memory impairments induced by sleep deprivation (SD) in the intact and ovarectomized (OVX) female rats. Two sets of animals including intact and OVX were randomly recruited into the following subgroups: control, SD, wide platform (Sham platform), caffeine, and caffeine plus SD. Multiple platform method was used for SD induction. Spatial learning and memory were determined using Morris water maze (MWM) task. Throughout behavioral investigation, significant learning impairment was observed in sleep-deprived OVX rats compared to the intact and the other OVX groups (P<0.05). Short term memory impairment was observed in both sleep-deprived OVX and intact groups (P<0.05). 4weeks caffeine administration improved these impairments. Based on these findings we propose that sleep deprivation impaired cognitive function whereas caffeine treatment reversed these impairments. D ow nl oa de d fr om w w w .p hy ph a. ir at 2 0: 20 IR S T o n T hu rs da y O ct ob er 1 3t h 20 16 122 | Physiol Pharmacol 19 (2015) 121-129 Esmaeilpour et al. related to sleep (Manber and Armitage, 1999). Previous studies suggested a neural basis for sex difference in hippocampus dependent learning task (Maren et al., 1994). Estrogen level can alter memory during the lifespan of the female. Indeed, when estrogen increases, dendrite spine density increase on pyramidal cells in the prefrontal cortex and hippocampus and improve memory functions (Luine and Frankfurt, 2013). Estrogen in its acute form facilitates the effect of glutamatergic transmission, and long-term potentiation (LTP) which provides a potential explanation for the considerable influence of steroid on behavior pattern. Recent works have identified the mechanism which underlies this synaptic action (Kramar et al., 2013). Caffeine is used commonly as a central nervous system stimulant (Ferré, 2008) which is found in several beverages and food. Caffeine has beneficial effects on cognitive impairment and neurodegenerative disease including Alzheimer’s and Parkinson’s disease because of its neuroprotective effects (Dall'Igna et al., 2004; Dall'Igna et al., 2007). Previous studies have shown that low doses of caffeine administration have positive effects on learning and memory (Angelucci et al., 2002); additionally chronic caffeine consumption prevents learning and memory impairment in Alzheimer disease (Dall'Igna et al., 2007). The beneficial effects of caffeine administration on memory may be related to its nonselective antagonistic effects on adenosine receptors (Takahashi et al., 2007; Pires et al., 2009). Indeed, another study has shown that caffeine prevents spatial short-term memory and E-LTP impairments induced by 24-h sleep deprivation in CA1 area of the hippocampus of male rats (Alhaider et al., 2010b). However, no information is available about the effect of caffeine administration on the damaging effects of SD on the cognitive function in female rats. The aim of the present study was to examine the effects of chronic caffeine treatment on SD-induced impairment of learning and memory in the intact and ovarectomized female rats. Materials and methods All experimental protocols and treatments were approved by the Ethical Committee of the Kerman Neuroscience Research Center (EC/KNRC/92-30) that was completely in agreement with the “NIH Guide for the Care and Use of Laboratory Animals”. Adult intact and OVX female Wistar rats, weighing 200– 250 g, were randomly assigned into five subgroups: Control, SD, wide platform (sham platform), Caffeine and Caffeine ⁄ SD. A sham surgery was also performed on a separate group of rats. All OVX and sham surgery (submitted to surgery without removing the ovaries) underwent ovariectomy surgical procedure (n = 8 for each group). Rats were caged individually and maintained under constant temperature (23 ± 1 °C) and 12-h light–dark cycle (light on at 07:00). They had free access to standard food and water. All female were bilaterally ovariectomized under general anesthesia (60 mg/kg ketamin and 10mg/kg xylazin). All of the ovarectomized rats were used after 1 month of surgery to prevent or minimize any hormonal influence originating from their reproductive cycle (Saadati et al., 2015) Caffeine (Sigma Aldrich) was orally consumed for 4 weeks in drinking water (0.3 g ⁄ L) (Alhaider et al., 2010b). The range of the daily consumption of caffeine by each rat was between 16–20 mg. The amount of water consumed by rats in the caffeinated groups during the 4 weeks was not significantly different than that of the control group. During sleep deprivation of the caffeine/sleep deprivation group, we added the same concentration of caffeine in the aquarium water in case the rats drink from aquarium water rather than water bottles. The rats in SD and caffeine ⁄ SD groups were sleepdeprived for 72 h using the columns-in-water method (modified multiple platform model). Four rats from the same cage were placed in an aquarium containing 10 circular platform platforms (10 cm height, 7 cm diameter) whose tops were 2 cm above the water. Platforms arranged in two rows and spaced 10 cm apart (edge to edge) so that the rats could move freely around by leaping from one platform to another. Because the animals can move freely within such multiplatform chamber, it is reported that they experience less immobilization stress compared to the widely used single platform model. Rats woke as they fell into the water each time they reached the REM sleep phase because of loss of muscle tone. During the D ow nl oa de d fr om w w w .p hy ph a. ir at 2 0: 20 IR S T o n T hu rs da y O ct ob er 1 3t h 20 16 Caffeine improved learning and memory in rat Physiol Pharmacol 19 (2015) 121-129 | 123 sleep deprivation period, rats had free access water bottles and food pellets baskets hanging from the top of the chamber. We also tested the effects of possible stress causing elements of the chamber environment by using a wide platform (15 cm in diameter), which allowed the rats to sleep without falling into the water (Hajali et al., 2012). The Morris water maze is one of the most greatly. Widely used models in behavioral neuroscience for evaluating the potential effects on spatial learning and memory in experimental manipulation. This device is a black circular pool (160 cm in diameter and 80 cm in height) that was filled to a depth of 40 cm with water and kept at room temperature. The pool was separated into four equal quadrants. A black square platform (10 cm in diameter) was centered in northeast quadrant of the pool and submersed 1.5 cm into the water so that it was imperceptible at water level. The experiments were done in the dimly lit light room with spatial cues which were attached to the walls around the maze at different points. Noldus Ethovision system, version 7.1, is a smart video tracing system that recorded the performance of rats. Also, it can be traced on the monitor of the computer. In this test there are three blocks with 30 minutes. Each block included four sequential trials each taking 60s (Inter-trial interval=30s). Rats were release randomly in the water maze while facing the wall of each quadrant. After each rat found the platform, it was allowed to stay there for 20s and then it was relocated to its cage to rest for 10s before starting the next trial. In case a rat did not discover the platform in 60s it was led to that platform by the experimenter. The data on time and distance to find the hidden platform were collected and analyzed later. A single probe trial was given 2 h after the last training trial to test the short term spatial memory in the water maze. In this trial the platform was removed and rat was allowed to swim for 60 s. The time and distance spent in the target quadrant (quadrant 4) were analyzed as a measure of spatial memory retention (Saadati et al., 2015). All comparisons among the groups were also analyzed with two-way ANOVA followed by Tukey's post hoc multiple comparison test. The averages for different groups also were compared using one-way ANOVA, followed by Tukey test. Data was explained as Means ± SEM of eight rats per group. The statistical significant level was considered as P < 0.05.