It may sound like a paradox to produce a drug that is used to treat drug addiction but this is a logical possibility according to studies published in Addiction Biology where investigators at the University of Bath discover a potential mechanism for fighting drug addiction relapse.
Drug relapse remains a major issue in addiction treatments. The majority of adult patients affected by addiction will return to drug use within 12 months of quitting. The issue is haunted by the 'opioid epidemic' of prescription as well as the recreational opioid drug use which includes morphine and heroin. Drug addiction relapse is related with drug-related cues such as certain environments here the drugs are consumed, drug paraphernalia, the drug by itself, as well as stress, which highlight the importance of memories and the role they hold in addiction relapse.
Researchers at Bath, along with colleagues from the University of Surrey and RenaSci, studied an animal model that allowed them to examine the animals relapse to morphine seeking behavior. The rat and mouse models learned to associate particular cues with morphine use. After drug removal, relapsing to the drug-use behavior happened as a result of receiving these drug cues again.
The Bath team wanted to specifically investigate the effect of using a brain blocker neurotransmitter better known as acetylcholine, which plays a significant role in memory processes. Investigators studied the effect of a ligand blocker of a specific acetylcholine receptor. This ligand or blocker is called the alpha7 nicotinic receptor, which was tested to see if this might impair relapse. Alpha7 nicotinic receptors are the main component of the intended drug, methyllycaconitine (MLA), which successfully blocked morphine relapse and is derived from Delphinium plants.
These novel observations researchers to examine the brain region responsible for MLA's effect and to identify the hippocampus as the locus, the part of the brain well known for its role in memory. Most importantly, they identified the ventral portion of the hippocampus that is accepted with emotional memories and obviously a link to addiction pathways.
Professor Sue Wonnacott, from the University of Bath's Department of Biology & Biochemistry, said: "It's an exciting step forward that links the cholinergic system, more commonly associated with nicotine addiction, with the mechanisms of relapse a different class of abused drug -- the opioids. More work needs to be done to uncover the brain mechanisms involved, but it raises the prospect of erasing long-term drug-associated memories that underpin addiction and the propensity to relapse."
Dr. Chris Bailey, from the University of Bath's Department of Pharmacy & Pharmacology, also added that "Drug addiction is very poorly treated at present so this potential novel approach is very welcome. An important next step is to see if MLA blocks relapse to other abused drugs. We already have evidence, in the same animal model, that it is effective against the more potent opioid, heroin. If MLA has similar effects against other drugs of abuse such as cocaine it would be even more encouraging."
Source: University of Bath, Addiction Biology