The following information is a summary of how drugs and alcohol impact the neurotransmitters in the brain. I gathered information from a variety of resources to create a simple summary. Most of the information comes from NIDA.
Effects on Neurotransmitters
Marijuana – Anandamide is an endogenous (naturally occurring) cannabiniod neurotransmitter which activates cannabinoid receptors in different parts of the brain. Endocannabanoids serve as an internal neuromodulatory system with at least 5 identified members. They are involved in appetite, pain sensation, mood, memory, synaptic plasticity. Marijuana (THC mimics anandamide) activates these internal receptors
Endocannabinoids are released just after neurons have fired and in some parts of the brain increase the firing rate of the neuron that had just released them. By increasing the action of the neurons that are already active, cannabinoids cause each thought, each response, each act of perception or imagination to magnify itself. This is what produces mental exploration when “high” but misses the “big picture” due to being so caught up in the momentum of the present reflection. Some brain areas have many cannabinoid receptors; others have few or none. Areas highly affected include the cerebellum and basal ganglia. In low to medium doses, marijuana can cause: relaxation, reduced coordination, reduced blood pressure, sleepiness, disruption in attention, an altered sense of time. In high doses, marijuana can cause: hallucinations, delusions, impaired memory, and disorientation.
Opiates – Opioid receptors are normally activated by endogenous neural endorphin chemicals. Heroin saturates these opioid receptors and creates euphoria. Opiate receptors are widely distributed in the brain and body. Opiates provide a calming feeling by inhibiting neurons activated by pain or stress and they also increase the flow of dopamine in the ventral striatum creating feelings of pleasure. Opiates relieve pain by blocking the transmission of pain messages between neurons and therefore prevent pain messages from reaching the brain (known as analgesia). Heroin penetrates the brain more quickly than other opiates. There are lots of opiate receptors on brain stem which controls breathing and misuse can result in accidental overdose.
Dissociatives – DXM (dextromethorphan - found in cough syrup), ketamine, PCP – (Phencyclidine also known as angel dust), glue and gasoline are all drugs that dissociate feelings from reality. These chemical block the NMDA (N-methyl-D-aspartate) receptors which are fundamental agents of synaptic plasticity which facilitate neural connections and learning. When NMDA receptors are blocked, “reality” stops getting through. A well-functioning brain synchronizes limbic (mid brain) meaning with the sense of the cerebral cortex and constantly flows in both directions. Dissociatives close down the coritco-limbic bridge so the limbic system is no longer constrained by the logic and reasoning of the cerebral cortex. Long term use results in memory loss and speech difficulties.
Hallucinogens – LSD (Lysergic Acid Diethylamide) – LSD looks just like serotonin molecules and binds tightly to these receptors. Once encamped in the receptors prevent the inhibitory, soothing, filtering, and regulating role of serotonin. The brain now responds to everything, including the tiniest fragments of thought and perception resulting in information overload. The brain loses its ability to integrate information causing widespread effects including emotional swings, altered perceptions, delusions and visual hallucinations.
MDMA (Ecstasy) – Causes neurons to release greater amounts of serotonin and dopamine than normal. MDMA can cause damage to serotonin containing neurons.
Stimulants:
Methamphetamine – Meth is strongest of all stimulant drugs. It is chemically similar to dopamine. This similarity allows methamphetamine to fool the dopamine transporter into carrying methamphetamine to the nerve terminal. Methamphetamine also directly crosses nerve cell membranes, and once inside nerve terminals, it enters dopamine vesicles and causes the release of these neurotransmitters. Result is high concentration of dopamine in the synapse activating and activating over and over. Norepinephrine and serotonin levels also become elevated in the synapse. It differs from cocaine in that it can damage neurons in frontal cortex, amygdala and striatum (brain region involved in movement). The message of meth is that goals do not matter anymore. When engorged on dopamine, the ventral striatum acts as if it’s pursuing goals, yet there are not goals. Long term used is associated with symptoms that mirror Parkinson’s disease of tremors, rigidity, balance and posture and motor difficulties.
Cocaine - Cocaine blocks the dopamine from leaving the synaptic gaps (prevents the reuptake) between the brain's neurons, and this leads to a buildup of dopamine; the brain then remains stimulated. Users often take cocaine in "binges," during which the cocaine is used repeatedly and at increasingly higher doses. This can lead to increased irritability, restlessness, panic attacks, and paranoia/psychosis. With increasing dosages or frequency of use, the risk of adverse psychological or physiological effects increases.
Alcohol – Alcohol has a widespread impact on the brain and impacts multiple neurotransmitters. Alcohol affects judgment, emotion, breathing/heart rate, and balance/coordination. Alcohol promotes GABA (gamma-amino butyric acid). GABA is a neurotransmitter that primarily works to inhibit the activity of neurons. Similarly, alcohol may inhibit/block release of the excitatory neurotransmitter glutamate. Some evidence suggests that alcohol may activate naturally occurring opioid and cannabinoid pathways. Alcohol enhances the functioning of GABA but long term use results in “rebound” causing a risk for seizure/heart attack if not slowly tapered. Benzodiazepines work on GABA so they are often used to aid symptoms of withdrawal.
Hypnotics - Hypnotics (prescription sleeping pills, benzodiazepines, barbiturates) binds to a subtype of GABA receptor. Again, GABA is a neurotransmitter that primarily works to inhibit the activity of neurons. When hypnotics bind to this receptor, it slows and stops activity in certain parts of the brain. They diminish activity in parts of the brain that are responsible for processing thoughts.
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