Ketamine, famed for its use as a horse tranquilliser, is being billed as the next big thing in the quest to find an effective treatment for depression. This is a drug that, according to FRANK, depresses the nervous system, causes a temporary loss of body sensation and has powerful hallucinogenic properties. Well, it's now been suggested that it takes on a more formal persona – distancing itself from its Class C role as the street drug 'Special K'. This was discussed back in summer 2010, but its potential has been lauded again in The Royal Society's recent collection of essays from their neuroscience project, Brain Waves.
Professor Barbara Sahakian, from the University of Cambridge, thinks that, following its success in recent proof-of-concept studies, it's the perfect candidate for industry to pursue and "would result in great benefits for patients with depression".
The past decade has seen research into depression focus on glutamate, which is a substance known as a neurotransmitter responsible for ferrying signals through the spinal cord and brain. It functions as part of an important signalling system in the brain, and there's evidence that alterations in the levels of glutamate can cause depression. Some scientists believe moderating the system in which it works is key to controlling the disease.
A study by the World Health Organisation suggested that by 2020 major depression would be a leading cause of reduced life expectancy, second only to ischemic heart disease. Less than a third of patients with major depressive disorder (MDD) achieve remission after a fortnight of treatment with standard antidepressants, which is echoed in the management of bipolar disorder.
Ketamine is particularly interesting because of its rapid action – in trials on patients with treatment-resistant MDD some showed improvements within only 40 minutes. Over 70% responded within 24 hours, reaching a level that took six to eight weeks to occur with traditional therapeutics. The drug inhibits proteins that interact with glutamate; it's thought that other antidepressants act on members of the same chain, but ketamine takes a short-cut, explaining why its effects are seen so quickly. More than that, the drug also sets off a series of events that lead to the formation of new synapses (the gaps between nerve cells where neurotransmitters are found) – another reason for its speedy results.
The set of essays also discusses the potentials of cognitive enhancing drugs whose actions improve memory and concentration. As many diseases exhibit the symptoms these drugs tackle, they could target anything from Alzheimer's to attention deficit hyperactivity disorder (ADHD). However they identify a rise in the amount of healthy individuals taking such drugs and Professor Trevor Robbins' essay notes that 'off-label' use is likely to become both a regulatory and ethical issue.
A good example of this is the American survey conducted last year that found a quarter of students using neuroenhancing drugs such as Ritalin and modafinil (used to treat ADHD and narcolepsy, respectively). However, a review by Lynch and colleagues, to be published in the journal Pharmacology Biochemistry and Behaviour, notes that there is a lack of studies conducted on modafinil use in healthy adults, and reports of both positive and negative effects of Ritalin. They write that more evidence is needed before definitive conclusions can be drawn on whether the effects translate into cognitive improvements throughout the brain, but that it's likely they would rely on the individual and the situation.
Module 2 in the Brain Waves series will discuss the implications of advances in neuroscience on education and lifelong learning.
