Neurotransmitter Mechanisms and the Effects of Cocaine and Heroin on the Central Nervous System

If someone were asked to identify the most lethal drugs commonly abused, it's likely that Cocaine and Heroin would be among their top picks. Though many haven't encountered these substances firsthand, they've probably seen representations of them in movies or heard stories of celebrities facing adverse consequences due to their use. Additionally, news of government agents intercepting drug trades has added to the public's familiarity with these drugs. Today, I'll be delving into the properties of these hard drugs and what we should understand about them.

The reasons behind drug use can be unclear, yet the effects of narcotics are consistent among users. When individuals consume these substances, they expect an increase in dopamine release, leading to feelings of euphoria, heightened stamina (in the case of stimulants), or relaxation (if it's a depressant). This occurs due to alterations in the central nervous system, which affect the activities of neurotransmitters depending on the specific drug used.

Both Heroin and Cocaine achieve the above-mentioned effects, albeit through different mechanisms. Dopamine is a familiar neurotransmitter responsible for providing feelings of satisfaction, pleasure, or reward. It acts as an "addiction neurotransmitter" because it encourages the repetition of certain activities.

During such activities, dopamine is released from presynaptic neurons into the synaptic space, where it binds to receptors on post-synaptic neurons, leading to pleasurable sensations. Afterward, dopamine is collected and recycled back into the presynaptic neurons.^,

When a person takes cocaine, it interferes with the reuptake of dopamine into the presynaptic neurons, allowing dopamine to be present and excessive in the synaptic space, and this is where the person gets the high pleasure. Cocaine starts to get broken down after about 40 minutes to 90 minutes after which the dopamine is recycled. Although the person gets the dopamine feeling, they still get the stimulating part of cocaine.^{, ,}

For individuals to experience the stimulant effects of cocaine, it must also interfere with another neurotransmitter called epinephrine or adrenaline. Similarly to dopamine, cocaine blocks the reuptake of epinephrine, leading to an increased amount of this neurotransmitter in the synaptic space. As a consequence, the user experiences an elevated heart rate, rapid breathing, and increased blood flow to muscles.

When a person overdoses on cocaine, there is excessive adrenaline in the body, causing the excessive firing of the nervous system which would lead to irregular heartbeat where the heart pumps excessively. When the heart pumps too hard, blood, as well as oxygen intake to the body is reduced because the heart would not contract and relax properly. This can cause heart attack, cardiac arrest, seizures, and strokes. In cases of excessive intake of cocaine, it can be fatal leading to death.

Heroin, also known as Diacetylmorphine, is another potent drug derived from morphine through a process called acetylation. This modification makes it more potent and allows it to easily pass through the blood-brain barrier. The most common route of administration is via injection (IV).

Heroin induces a high by affecting dopamine release, which is achieved by inhibiting the release of Gamma-aminobutyric acid (GABA). GABA's function is to balance the excitatory states of neurons, so its inhibition leads to the uncontrolled release of dopamine.

The effects of heroin include increased euphoria and reduced sensation of pain, which is why it was used as an analgesic in the past. The drug binds to Mu-receptors in the central nervous system, which reduce pain sensation by decreasing sensory transmissions in the spinal cord.

Heroin overdose depresses the nervous system thereby leading to slower breathing which can cause respiratory failure, as a result of suffocation. Below the medulla is a neuron known as Pre-botzinger complex which controls respiration when activated by opioids. These neurons inhibit the transmission that controls breathing in the nervous system, and this leads to respiration failure and death.^{, ,}

While both Cocaine and Heroin are extremely dangerous on their own, individuals who overdose often take them in combination, known as polydrug use. This can lead to a more pronounced effect on dopamine, and until one drug wears off, the impact on the heart may not be readily noticeable. Given that Heroin has a longer duration of action, it can still cause the heart rate to slow down, potentially leading to death.^{, , ,}

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Image Reference

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• Image 1 || Need Pix || Cocaine Speed Amphetamine Free Photo
• Image 2 || Wikimedia Commons || Cocaine