When opiates enter the brain they disperse and start bumping into neurons. Some neurons have what’s known as opioid receptors on their surface. When an opiate bumps into an opioid receptor attached to a neuron within the Ventral Tegmental Area (VTA) of the brain it will activate what’s called an opioid circuit. These opioid circuits are what make users feel good. This feel-good sensation is one of the primary factors in the development of opiate addiction.
So what is a neuron?
Neurons are simply nerve cells. Interneurons, as shown above, are nerve circuits i.e. two or more neurons working in concert to create a specific response. Interneurons are primarily found in the brain and spinal cord and they carry the information that allows us to think, act, learn, and feel.
A good way to think of a neuron is to think of a tree, with roots, a trunk and branches. The roots, or dendrites, are the main apparatus for receiving information. This information passes through the base of the trunk, or cell body, which processes the information. The processed information is sent up the trunk, or axon, which disperses the new information through the branches, or axon terminals, which releases the new information as falling leaves, or neurotransmitters, out to other neurons and so on and so forth.
The following describes how opiates create the sensation of pleasure, which for some men and women, can lead to addiction.
- GABA neurotransmitters are inhibitory substances, i.e. they stop other neurons from activating. In fact, GABA neurotransmitters are the main inhibitory neurotransmitters in the brain.
- Opiates mimic inhibitory neurotransmitters, but since they attach to GABA neurons they stop GABA neurotransmitters from being released.
- Opiates basically stop the stoppers.
- Without GABA stopping Dopamine neurons, Dopamine neurons begin releasing Dopamine neurotransmitters into the Central Nervous System (CNS), where it activates other neurons, and ultimately creates the sensation of reward or pleasure.
Opiates like morphine and its synthetic analogs opioids, are used in the treatment of acute and chronic pain. Now we understand that morphine and other opiate drugs act on neuron circuits and opioidergic systems. Not only are opiates and opioids involved in controlling pain, but they also act on the reward pathway. They also modulate gastrointestinal, endocrine, autonomic and cognitive functions.
Repeated administration of opiates:
Opiates attach to the same opioid receptors as endorphins, that is to say, opiates exert their drug effects by mimicking endorphins. Your body’s endorphins are your private stock of narcotics. Endorphins are released by the pituitary gland in response to stress or pain. However, opiates are much stronger than endorphins, and therefore produce much greater drug effects.
One of the side effects of repeated opiate use is suppression of endorphin production. Consequently you become depleted of endorphins. In time, you will not have an adequate supply of natural painkillers, if and when you need them. Another common side effect of opiate use is the development of hyperalgesia, which is a greater sensitivity to pain. Things that normally never caused you pain, suddenly do cause you pain. This is the paradox of opiate drug use. At first everything is great, then suddenly, you’re miserable without them.
Adverse drug effects
The euphoric, analgesic, sedative and respiratory effects of opiates have been known since early history. However, unintended sedation and respiratory depression are two of the most serious problems with using opioids and this is what limits its safety and usefulness. There is another factor that’s often overlooked, that opioids kill people and not just by overdose. Some people fall down and hit their head while others crash their car. In fact, no other medication kills more people.
Actions of opiates
Opiates affect the brain because they are able to bind to and activate μ-mu opioid receptors, which are the most prevalent opioid receptors and also most responsible for opioid drug effects.
- Analgesia – pain relief
- Euphoria – feeling of pleasure caused by increased dopamine
- Sedation – sedation generally precedes significant respiratory depression
- Respiratory depression – dual complimentary effects of mu and delta opioid receptors
- Cough suppression – antitussive
- Anti-diarrheal – causes constipation
Opiate side effects
Opiates may cause side effects on the cardiovascular system, thermoregulation, hormone secretion and immune function. However, multiple factors, such as opiate type, dose, formulation, route of administration, duration of therapy, concomitant medications, and general health, can influence the occurrence of side effects. Major side-effects associated with opiate use include the following:
Short-term Side Effects
- Constipation – common side effect unaffected by tolerance
- Urine retention – common side effect unaffected by tolerance
- Pinpoint pupils – common side effect unaffected by tolerance
- Nausea – common side effect, that may require anti-nauseants
- Wheal, flare and itchiness reactions on skin
- Decreased secretion of norepinephrine
- Hypotension – low blood pressure
Long-term Side Effects
- Dependence- susceptible to withdrawal
- Addiction- compulsive seeking and using
- Lower testosterone levels – side effect of suppressed hypothalamus
- Skipped menses
- Decreased conative ability
- Decreased cognitive ability
- Impaired short-term memory
- Delayed verbal memory
- Increased secretion of norepinephrine
Hazards of opiates
The most dangerous effect of opiate use is overdose. Opiate overdose fatality is defined as a fatality due to respiratory failure following opiate consumption. Overdose occurs when the brain centers that control respiration relax and forget to breath. This results in periodic gasping for air. Eventually the brain forgets to gasp, which results in respiratory failure and eventual death. Studies suggest that on average opiate overdose takes approximately 3 hours. On the other hand, opiate toxicity fatality can result in death in just a couple of minutes.
Signs of Opiate Overdose:
dopamine (DA): Dopamine is a neurotransmitter synthesized from tyrosine in various regions of the brain and is involved in many neurological pathways and processes. Dopamine is an inhibitory neurotransmitter, meaning that when it finds its way to its receptor sites, it blocks the tendency of that neuron to fire. Dopamine is present in brain regions that regulate movement, emotion, motivation, and the feeling of pleasure. As it turns out, dopamine plays a fundamental role in almost all aspects of human behavior: from motor control to mood regulation, cognition, addiction, and reward. The general rule is, if it feels good, dopamine neurotransmitters are probably involved. Drugs like heroin, alcohol, cocaine and nicotine all increase the brain’s release of dopamine. Dopamine is responsible for the motivation required to seek pleasure while opioid systems are accountable for our experience of pleasure. Thus dopamine is needed for “wanting”, while opioids are necessary for “liking”.
locus ceruleus (LC): A region of the brain that receives and processes sensory signals from all areas of the body; involved in arousal and vigilance.
μ-mu opioid receptor:A receptor on the surface membrane of nerve cells that mediates opioid analgesia, tolerance, and addiction. Opioids affect your brain because they cross the blood brain barrier then bind to and activate μ-mu opioid receptors, the receptor most responsible for opioid affects.
noradrenaline (NA): A neurotransmitter produced in the brain and peripheral nervous system; involved in arousal and regulation of blood pressure, sleep, and mood; also called norepinephrine.
ventral tegmental area (VTA): The ventral tegmental area, or VTA, is a group of neurons in the midbrain. The VTA is primarily characterized by its dopaminergic neurons, which is considered an integral part of the body’s reward system, which is involved in reinforcing behavior.