- opioids narcotics (activate opioid receptors)
- nicotine (activate nicotine receptors)
- marijuana (activate cannabinoid receptors)
- alcohol (activate GABA receptors; an inhibitory transmitter) Drug like cocaine & Ritalin affect Neuronal Terminal Transport. Drugs like Amphetamines –methamphetamine -MDMA (Ecstasy) release DA from vesicles and reverse Transporter.
- Slowed gait
- Impaired balance.
- Good News: After 2 years, some of the dopamine deficits are recovering
- Bad News: Functional deficits persist
Brain Area Involvement:
For Amphetamines, Opiates, Cocaine, Cannabinoids, Phencyclidine, Ketamine- Peri Basal Ganglionic areas affected.
For Opiates, Ethanol, Cannabinoids, Barbiturates, Benzothiazepines, Nicotine- Midbrain and supero hypothalamic areas affected.
Effects of Drugs on Dopamine Release
Amphetamines cause much greater activity than Nicotine, Cocaine and Ethanol—they all cause Neurotoxicity.
There is decrease in metabolism in the Orbito Frontal Cortex (OFC)-seen on Positron Emission Tomography analysis. Dopamine Transporter Loss is seen after heavy Methamphetamine use.Motor Function is affected to cause
Impairment correlates with damage to the dopamine system.Implication:
Brain changes resulting from prolonged use of psycho stimulants such as methamphetamine, maybe reflected in compromised cognitive and motor functioning.Is There Recovery?
What does this mean???
The ability to experience Reward is damaged.
(A comparatively decreasing order of reward sensation is experienced: from cocaine -to methamphetamines -to alcohol, with Cocaine being the least. Food, sex and nurturing provide comparatively only about 20% efficacy).Summary:
Addictive drugs activate the reward system via increasing dopamine neurotransmission. The reward pathway is associated with several drugs that have addictive potential.
Just as heroin (morphine) and cocaine activate the reward pathway in the VTA and nucleus accumbens, other drugs such as nicotine and alcohol activate this pathway as well, although sometimes indirectly (through the globus pallidus, an area activated by alcohol that connects to the reward pathway).
While each drug has a different mechanism of action, each drug increases the activity of the reward pathway by increasing dopamine transmission.
Because of the way our brains are designed, and because these drugs activate this particular brain pathway for reward, they have the ability to be abused. Thus, addiction is truly a disease of the brain.
This knowledge will in time help to find an effective treatment strategy for the recovering addict.
Dr M. S. Menon,
MD., Major (Retd) AMC.,
Director, Kripa Foundation.
01 December 2014