Drugs: A New Form of Communication


How Drugs of Abuse Interfere with the Neurotransmission at the Synapse

- Drugs of abuse get into the body, and more significantly, into the brain and effect neurotransmission at the synapse. Some drugs act as antagonists, while others act as agonists, producing different effects. Some block receptor sites where naturally produced neurotransmitters (NT) usually bind. Other drugs block reuptake channels, but in general, all drugs effect the natural cycle that neurons undergo.


Drugs can affect synapses at a variety of sites and in a variety of ways, including:
1. Increasing number of impulses
2. Release NT from vesicles with or without impulses
3. Block reuptake channels or block receptors
4. Produce more or less NT
5. Prevent vesicles from releasing NT

Route of Administration and How it Effects Effects of Drugs

Inhalation: Inhalation is the quickest method for a drug to reach and affect the brain. Upon inhalation, the drug travels from the lungs, to the left side of the heart, and then to the brain. Effects, however, do not last long because the drug is broken down by the liver very quickly. Inhalation does not provide the most intense effect due to the fact that the drug must pass through alveoli membranes in the lungs, and consequently decreasing the concentration of the drug and decreasing its effects. However, these membranes have such a small effect that the intensity is still very high. Inhalation makes the drug reach the brain the fastest, and thus gives the greatest chance for addiction
Injection: Effects are not registered as quickly as with inhalation. The drug has to go to the right side of the heart, to the lungs, and to the left side of the heart before finally reaching the brain. The drug is delivered to liver rather quickly, so effects do not last very long. There is, however, a high intensity because there is no decrease in concentration. Full amount of the drug will take effect.
Snorting/Snuffing: This method takes a long time to travel through nasal passageways and cranial bones. It does not produce an effect as intense as other methods because the drug gets caught in mucous membranes, and as a result, the concentration of the drug decreases. The duration of the effects are, however, lengthened because the drug remains in the body longer. Also, over time, addicts will get a higher intensity because the cells in the nose begin to die.
Ingestion: This method provides the longest effects due to the length of the digestive process. It takes a longer time for the drug to travel through the stomach where some of it dissolves. It then has to push across the thick mucus lining of the stomach before entering the blood stream to be sent to the liver. There, some more of it gets broken down by enzymes. All of this takes place before the drug reaches the brain, causing a less intense effect.




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Drug Administering Methods



Caffeine: Effects on Biochemistry


  • Caffeine is the same shape as Adenosine, a neuromodulator that decreases firing in the post synaptic neuron. It binds to its neuromodulator receptor. Since Adenosine is a natural sedative for the body, when caffeine blocks its receptors, the body gets a jolt of energy. Adenosine also increases vasodilation and is important for deep restful sleep. When caffeine binds to the receptors, it increases impulses in the post synaptic neuron in comparison to normal because caffeine prevents the inhibition by adenosine. This increases heart rate. Caffeine also causes an increase in the release of epinephrine; this fools the body into a fight or flight response mode. Dopamine levels also rise slightly by caffeine blocking reuptake channels(this isn't 100% certain).
  • The half life of caffeine in the body is 6 hours. Since the average cup of coffee has 120 mg of caffeine, 6 hours later there is still 60 mg left in the body. Since caffeine has such a long half life, consumers can get stuck in a cycle of restless sleep and a desire for more caffeine- when a person consumes caffeine, they may go to bed with some of it still in their system which will cause a restless night of sleep and a desire to again consume caffeine the next day to compensate. This creates a habit forming cycle.
  • Caffeine is an inhibitor of the enzyme Camp-phosphodiesterase (cAMP-PDE), which converts cyclic AMP (cAMP) in cells to its noncyclic form, allowing cAMP to build up in cells. Cyclic AMP participates in activation of Protein Kinase A (PKA). By blocking its removal caffeine intensifies and prolongs the effects of epinephrine and epinephrine-like drugs, such as amphetamines and methamphetamines. By preventing the decomposition of cAMP into its non-cyclic form, it prolongs the effects of epinephrine on the cell. Increased concentrations of cAMP in cells causes an increased activation of protein kinase A (PKA) which in turn results in increased gastric acid secretion by the cell.
  • As we have studied, caffeine inhibits the adenosine neuromodulator on the postsynaptic neuron. In the picture below, caffeine interrupts the cycle of homeostasis of cAMP levels and mimics the effects of epinephrine. By preventing the decomposition, it artificially keeps the cAMP levels high as if the epinephrine was continually activating the G-protein to convert ATP into cAMP.



Action of Major Medications that Work at the Synapse


Prozac Fluoxetine (Prozac) is a member of the class of antidepressants known as selective serotonin reuptake inhibitors, because it preferentially inhibits the transport of serotonin into presynaptic nerve terminals and exhibits negligible affinity for a number of neurotransmitter receptor subtypes. (Methylphenidate) affects the synapse in a way that is similar to amphetamines, however in a more mild manner. It is an agonist to Dopamine and Norepenephrine; neurotransmitters in our brain that regulate arousal and attention. Normally, the transmitter fires the chemical into the synapse. the next transmitter accepts the chemical, sends the signal on, and the chemicals are recycled back into the sending transmitter; a process called "re-uptake". What ritalin does is it blocks the re-uptake of the neurotransmitter, so more stays in the synapse, therefore creating a stronger signal throughout the brain. When these two neurotransmitters are affected in this way, it causes a feeling of arousal because of the dopamine excess, and mental clarity and focus, because of the noropenephrine excess.

Ritalin (Methylphenidate) affects the synapse in a way that is similar to amphetamines, however in a more mild manner. It is an agonist to Dopamine and Norepenephrine; neurotransmitters in our brain that regulate arousal and attention. Normally, the transmitter fires the chemical into the synapse. the next transmitter accepts the chemical, sends the signal on, and the chemicals are recycled back into the sending transmitter; a process called "re-uptake". What ritalin does is it blocks the re-uptake of the neurotransmitter, so more stays in the synapse, therefore creating a stronger signal throughout the brain. When these two neurotransmitters are affected in this way, it causes a feeling of arousal because of the dopamine excess, and mental clarity and focus, because of the norepinephrin excess.