by Pakinee Pooprasert
Parkinson’s is a progressive disease where the brain becomes damaged over many years, with the classical symptoms being tremor (involuntary shaking of particular parts of the body), slow movement and stiff and inflexible muscles. Currently patients with Parkinson’s are given multiple drugs to slow down the disease progression, and many studies are conducted with the aim of finding a Parkinson’s cure or treating it more effectively.
In a revolutionising study, Italian neuroscientists report that the brain cells of people with Parkinson’s disease can respond to inert (placebo) drugs. This response wears off after one day, but the effects demonstrates that it might be possible to reduce the medication needed to treat this disease by interspersing real drugs with placebo injections or pills. While a few patients did not respond dramatically to the placebos, most did and this poses a very promising future for the field.
In patients with Parkinson’s, the characteristic tremors and stiff muscles are due to the death of dopamine-producing brain cells. Currently, doctors alleviate these symptoms by prescribing drugs such as apomorphine, which activates dopamine receptors.
Additionally, for conditions such as pain and immune disorders, trials have shown that it is possible to train people to respond to placebos, and this made Benedetti and his colleagues – researchers who led the work at the University of Turin – wonder whether the same applies for neurological disorders.
The study involved 42 people with advanced Parkinson’s disease who were having deep brain stimulation, allowing Benedetti’s team to measure the activity of individual neurons in the thalamus, a region that is inhibited by lack of dopamine in Parkinson’s patients.
During the surgery for deep brain stimulation, participants were given a saline injection which was told to be apomorphine. Interestingly, it produced no response, unless the patients had been preconditioned by having received 1-4 daily injections of the actual drug before the surgery. It was observed that neurons showed increased activity and muscle rigidity dropped in patients who did respond to the saline after the injection. This was assessed by a neurologist who was not told of the purpose of the study, to prevent any bias.
Furthermore, it was found that the larger the number of previous apomorphine injections, the greater the subsequent response to the saline. This meant that if the patients had received four previous injections, there was “no difference between drug and placebo response,” Benedetti explained.
While this training is short lived, it only lasted a maximum of 24 hours, Benedetti hopes that it may be possible to lengthen the placebo ‘memory’ of patients by giving them the real drugs for longer.
Why is this study revolutionary? “Because of its clear demonstration that clinical response and neurological activation are clearly linked and can be trained,” stated Christopher Goezt, a neurologist at Rush University Medical Centre in Chicago, Illinois. Furthermore, “Though the group sizes are small, the results seem compelling,” says Tor Wager, another neuroscientist at the University of Colorado Boulder. In addition, Espay, a neuroscientist at the University of Cincinnati in Ohio who has studied placebo effects in Parkinson’s predicts that placebos could ultimately be used in clinical practice to reduce the amount and cost of medication.
Despite the clear results, what remains unclear is how exactly the effects works. Goetz postulates that it may be a ‘Pavlovian response’, in which patients conditioned through experience associate injections with symptomatic relief.