Caffeine use prevents stress-induced impairment of spatial memory

A study conducted in Turkey discovered that adding caffeine to the drinking water of rats exposed to social isolation stress can protect them from developing spatial memory impairments. While rats who did not drink caffeine with water showed spatial memory impairments as a result of stress, these impairments were absent in rats who drank water with caffeine. The research was recently published in Developmental Neuroscience.

Caffeine is a natural stimulant that primarily affects the central nervous system. It provides a temporary boost in energy and alertness. Caffeine is found in various plants, including coffee beans, tea leaves, and cacao pods, making it a common ingredient in beverages like coffee, tea, and chocolate. When consumed, caffeine blocks the action of a neurotransmitter called adenosine. This neurotransmitter promotes relaxation and sleepiness, so blocking it results in increased wakefulness and alertness.

Caffeine also induces changes in specific genes associated with strengthening and weakening of connections between neurons (i.e., synaptic plasticity) in the hippocampus region of the brain. Another factor that is known to affect synaptic plasticity in the hippocampus is stress. The hippocampus is essential in the formation of new memories, including memories related to spatial features of one’s surroundings, but also those related to facts and events. Previous studies indicated that caffeine can prevent memory deficits and destruction of synapses connecting neurons.

Study author Seval Musuroglu Keloglan wanted to investigate the effects of caffeine on behavioral and neurochemical changes related to learning and memory function caused by stress. They conducted an experiment on mice exposed to social isolation. Social isolation is a well-established stress factor that causes changes in the whole body. It affects the neurochemical and neuroendocrine systems of the body both in humans and in many other animals.

The research was conducted on 28 Wistar albino male rats, 21 days old at the beginning of the experiment. The rats were housed in a controlled environment with a 12-hour light/dark cycle and a temperature of 21 degrees Celsius, with free access to food and water.

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The rats were randomly divided into four groups, each consisting of seven rats. One group underwent social isolation stress, another received caffeine in their water, the third group experienced both social isolation stress and consumed caffeinated water, and the fourth group served as the control, living normally without any special treatments. The caffeine-exposed groups had 0.3 grams of caffeine per liter of water, resulting in a daily intake of approximately 1-2 mg/kg of caffeine. Social isolation stress was induced by housing selected rats individually for four weeks, with minimal handling and reduced noise, thereby limiting their social interactions.

After four weeks of treatment, the rats’ learning and memory functions were assessed using the Morris Water Maze Test. This test involves placing a rat in a large circular tank filled with water, where it must find an escape platform that is hidden just below the water’s surface. The pool is surrounded by various visual cues, and the rat must use these cues to navigate and remember the platform’s location over repeated trials. This test is extensively used in neurological research to study cognitive functions, the effects of brain injuries, and the efficacy of treatments for conditions affecting memory and spatial learning.

This test was performed over five days. The first day was the habituation day. On this day, if a rat could not find the platform within 120 seconds, the experimenter would use a wooden stick to force it onto the platform and allow it to rest there for 10 seconds. Learning training was conducted by throwing each rat into the water from various corners five times between days 1 and 4 of the test.

Results showed that there were no differences in weight between rats from different groups after the treatment. However, rats in the social isolation group showed impaired spatial memory in the Morris Water Maze Test compared to the control group. Examination of brain tissue of these rats showed that the control and caffeine only groups, but also the group that was exposed to both social isolation and caffeine, had normal shapes of neurons.

On the other hand, the study authors found various irregularities in the appearance of neurons of rats from the group exposed to social isolation stress but not to caffeine. “[Social isolation] impaired spatial memory and caused morphological changes in adolescent rats, but this effect of isolation was not seen in caffeine-treated animals,” they concluded.

The study sheds light on the effects of caffeine on the brains of rats exposed to stress. However, it should be noted that the study was conducted on rats and not on humans. Although rats and humans share many physiological similarities, they also differ in many other areas. The effects on humans might not be the same.

The paper, “Effect of caffeine on hippocampal memory and levels of gene expression in social isolation stress”, was authored by Seval Musuroglu Keloglan, Leyla Sahin, Sayad Kocahan, Ebru Annac, Nurhan Tirasci, and Ayper Boga Pekmezekmek.