Garlic Improves Memory in Mice

Aged Garlic May be a Useful Treatment for Alzheimer's Disease

 

Take Home Message: Consuming aged garlic extracts improved memory and learning in rodents. Scientist believe garlic may help treat humans with Alzheimer's disease too (Ray et al. 2011).

Is your mouse having problems finding her way home? Adding aged garlic extract may allow her to find her way. Chronic garlic consumption has been shown to enhance memory in numerous rodent trials (Chauhan and Sandoval 2007, Haider et al. 2008, Ray et al. 2011, Jeong et al. 2013, Mukherjee and Banerjee 2013). Garlic increases brain serotonin concentrations in rats (Haider et al. 2008). Higher brain serotonin concentrations are associated with improved cognitive performance in many species, including humans. (Note: if you are having trouble with your memory or learning skills you may be depressed. See our page on depression symptoms to learn more).

Feeding mice a crude garlic extract partially reversed the effects of a drug, Scopolamine, which acts as a amnesic in mice. It also increased memory and learning in control mice (Mukherjee and Banerjee 2013). Mice were given garlic extract (40mg/kg/day) for 21 days. The garlic significantly improved learning and memory both in control mice and in scopolamine induced amnesic mice (Mukherjee and Banerjee 2013). Likewise, an earlier trial found that mice given garlic for 21 days had a significant improvement in memory (Haider et al. 2008).

In a similar study, mice were cognitively impaired by injecting them with a neurotoxin, amyloid beta protein (Aβ). Aβ proteins form insoluble plaques in the brain. They can bind to receptors on nerve cells and erode their synapses. This destroys the cell's ability to communicate and induces brain oxidative stress and formation of reactive oxygen species (ROS). Aβ is present in dementia and may be one of the major causes of Alzheimer's disease (Walsh and Teplow 2012).

Mice impaired by the Aβ neurotoxin performed significantly worse than control mice on the memory test. In contrast, mice injected with the Aβ neurotoxin and given ethyl acetate extracts from aged garlic in their water exhibited an attenuated Aβ-induced impairment on tests. In other words, eating garlic helped protect against the neurotoxin's ill effects. The more garlic extract the mice received, the better they did on learning and memory. In fact, mice given the highest dose of ethyl acetate actually did better than the normal control mice in tests (Jeong et al. 2013). In a similar study, feeding aged garlic to mice with the rodent's version of Alzheimer's disease prevented deterioration of hippocampal based memory tasks (Chauhan and Sandoval 2007).

Mechanisms by which Garlic Enhances Cognitive Function:

Garlic increases serotonin concentrations in the brain (Haider et al. 2008). High serotonin concentrations are associated with improved brain functions such as learning, memory and mood.

Aged garlic extract inhibits cortical acetylcholinesterase (AchE) while increasing glutathione (GSH) concentrations (Mukherjee and Banerjee 2013). GSH is a potent internal antioxidant that protects brain cells from free radical damage. Some treatments for Alzheimer's disease use AchE inhibition. AchE inhibition may affect executive and attentional cognitive functions (Bohnen et al. 2005).

Ethyl acetate extracts from aged garlic protects nerve cells from Aβ-induced ROS generation in vitro (Jeong et al. 2013).

Aged garlic compounds, in particular S-allyl-L-cysteine, protects neural cells from ROS. Interestingly, pretreatment of cells with garlic extract protected 80% of cells from ROS-mediated damage. It also protected pre-synaptic proteins (Ray et al. 2011). This may be beneficial in treating Alzheimer's Disease (Chauhan and Sandoval 2007, Ray et al. 2011).

 

How is Memory and Learning Accessed in Mice?

Mice are placed in a Y-maze test to measure willingness to explore new environments. Rodents prefer to explore a new area, or new 'arm' of the Y-maze, rather than returning to an area that was previously visited. This test uses a maze shaped like a Y. The mouse is placed in the center of the maze and allowed to explore freely for a predetermined length of time. Smarter mice will explore more new areas and remember where they have already explored.

In the passive avoidance test mice learn to avoid an unpleasant environment. Normally there is a light side and a dark side of a chamber. One side of the chamber is also associated with a mild foot shock. Smarter mice with better memory will quickly learn to avoid the side that shocks.

More on Scopolamine

Scopolamine is a belladonna alkaloid which is extracted from one of North America's most toxic plants, Deadly Nightshade or Belladonna (Atropa belladonna). Belladonna is so toxic that eating a single leaf or 2-5 berries can be lethal to an adult human. Scopolamine can also be extracted from other plants in the Solanaceae family including the Colombian Borrachero tree. Borrachero means "get-you-drunk".

Scopolamine is normally used to treat extreme motion sickness, vomiting or gastrointestinal spasms. In the past, it has been used as an anesthetic for surgery, as a poison, and to make poison tipped arrows. Unfortunately, this drug also has a modern day dark side.

Scopolamine is known as "The Devil's Breath" and the "Zombie Drug". It has been dubbed the "World's Scariest Drug". This colorless, odorless and tasteless drug can be added to people's food or drink to cause unconsciousness, loss of free will and docility. Illegal scopolamine use is a huge problem in Colombia. Criminals use this drug to rob, rape, prostitute, kidnap or harm unsuspecting marks easily. They add scopolamine to unsuspecting victim's drinks or food. Drugged people have withdrawn money from ATMs for the criminals, willingly handed them their belongings or helped them rob their own house! Afterwards, the person wakes ups disorientated and with retrograde memory loss.

Part of the problem with this scary drug is that people are extremely submissive or zombie-like under its influence. People seem to lose their ability to exercise free will. There is debate about whether people lose their free will or just become very disorientated. Either way, the victim usually becomes submissive. Victims can be kept drugged and docile for days while criminals use them for their own evil purposes.

Both the USA and Canada have issued warnings against travel to Colombia due to this problem. If you do travel to Colombia beware of leaving any food or drink unprotected. Scopolamine, known as Burundanga in Colombia, is also given to unsuspecting people in chocolate, chewing gum, cigarettes, drinks or concealed in a piece of paper and blown in their face.

How does Scopolamine work?

Scopolamine works by outcompeting acetylcholine in the brain. Acetylcholine is necessary to form memories. Scopolamine blocks acetylcholine access to neuron receptors during memory formation so that the memory is never formed. In addition, scopolamine seems to have an effect on free will which makes people unusually docile. It may influence the amygdalae, or decision making part of the brain. More research needs to be done on this theory, however. This drug was used as a truth serum by the CIA in the middle of the 20th century. They discontinued using it due to the side effects such as hallucinations, blurred vision, headache, rapid heart rate and death.

References:

Bohnen NI, Kaufer DI, Hendrickson R, Ivanco LS, Lopresti BJ, Koeppe RA, Meltzer CC, Constantine G, Davis JG, Mathis CA, Dekosky ST, Moore RY. Degree of inhibition of cortical acetylcholinesterase activity and cognitive effects by donepezil treatment in Alzheimer's disease. J Neurol Neurosurg Psychiatry. 2005;76:315-9. Pubmed. Full text.

Chauhan NB, Sandoval J. Amelioration of early cognitive deficits by aged garlic extract in Alzheimer's transgenic mice. Phytother Res. 2007;21:629-40. Pubmed.

Haider S1, Naz N, Khaliq S, Perveen T, Haleem DJ. Repeated administration of fresh garlic increases memory retention in rats. J Med Food. 2008;11:675-9. Pubmed. doi: 10.1089/jmf.2006.0229

Jeong JH, Jeong HR, Jo YN, Kim HJ, Shin JH, Heo HJ. Ameliorating effects of aged garlic extracts against Aβ-induced neurotoxicity and cognitive impairment. BMC Complement Altern Med. 2013;13:268. Pubmed. doi: 10.1186/1472-6882-13-268

Mukherjee D, Banerjee S. Learning and memory promoting effects of crude garlic extract. Indian J Exp Biol. 2013;51:1094-100. Pubmed.

Ray B, Chauhan NB, Lahiri DK. Oxidative insults to neurons and synapse are prevented by aged garlic extract and S-allyl-L-cysteine treatment in the neuronal culture and APP-Tg mouse model. J Neurochem. 2011;117:388-402. Pubmed. doi: 10.1111/j.1471-4159.2010.07145.x (full text)

Ray B, Chauhan NB, Lahiri DK. The "aged garlic extract:" (AGE) and one of its active ingredients S-allyl-L-cysteine (SAC) as potential preventive and therapeutic agents for Alzheimer's disease (AD). Curr Med Chem. 2011;18:3306-13. Pubmed. Full text.

Walsh DM, Teplow DB. Alzheimer's disease and the amyloid β-protein. Prog Mol Biol Transl Sci. 2012;107:101-24. Pubmed. doi: 10.1016/B978-0-12-385883-2.00012-6