The paper describes some interesting new findings that are likely to inform …

• (Abstract)
• The Dopaminergic Pathway
• Alcohol Withdrawal: the role of glutamate
• Opioid Dependence: what other neurotransmitter systems are involved?
• Ecstacy: the 5-HT system and neurotoxicity
• The Gabaergic System: target for sedatives
• Conclusion
• References

Biology Articles » Neurobiology » Neurobiology of Diseases & Aging » Neurobiology of addiction and implications for treatment » Opioid Dependence: what other neurotransmitter systems are involved?

Opioid Dependence: what other neurotransmitter systems are involved?

- Neurobiology of addiction and implications for treatment

Opioid Dependence: what other neurotransmitter systems are involved?

As described above, the mu opiate receptor plays a key role in opiate reward, but many of the mechanisms underlying opiate tolerance, dependence and withdrawal remain elusive. As the opiate receptor may not change with chronic opiate exposure, changes ‘downstream’ of the receptor may be more critical. For example, noradrenergic overactivity is seen in opiate withdrawal and can be treated with ₂ agonists such as lofexidine or clonidine (Strang et al, 1999).

In the treatment of opiate addiction, methadone is the most commonly prescribed drug, although the use of buprenorphine is increasing. Methadone (like heroin) is a full agonist at the mu receptor, whereas buprenorphine is a mu partial agonist. Partial agonists give lower levels of response at maximal receptor occupancy. Also, when a partial agonist occupies receptors, fewer are available for a full agonist (e.g. heroin). The partial agonist is therefore acting as an antagonist. Consequently, buprenorphine will stimulate the mu opioid receptor, but not maximally (hence, there is less risk of respiratory depression in overdose), and will also prevent the effects of heroin taken ‘on top’. In addition, its longer half-life allows less than daily dosing, an advantage in supervised consumption.