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How Do Drugs Affect Synapses?

Updated on May 17, 2012
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Drugs increase or decrease the effects of neurotransmitters. A drug that works against or blocks the effects of a neurotransmitter is defned as an antogonist. A drug that increases or pushes the effects is defined as an agonist. Some drugs can be both. This type of drug is called a mixed agonist-antagonist. This drug can be either depending on the dose. In other words it can be agonist at some doses and antagonist at other doses.

Drugs effect synaptic activities in quite a few ways. For a dopamine synapse, a drug can decrease or increase the sythesis of the neurotransmitter or even cause it to leak at its vesicles. It can increase its release, block its breaking down process, decrease its reuptake, inactivate chemicals, or even stimulate or stop the postsynaptic receptors.

Researchers say that a drug has an affinity for a specific type of receptor if it attaches or binds to that receptor. Some researchers have explained it sort of like a lock and a key.

Drugs differ in their affinity from strong to weak. The tendency to activate the receptor is the efficacy of a drug. For instance, a drug that binds to a receptor but does not stimulate it is said to be high in affinity but low in efficacy. This type of drug would be an antogonist because it occupies the receptor and prevents the effects of transmitting.

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Drugs Effect Each Person Differently:

Each drug affects many kinds of synapses. Antipsychotic drugs block, for the most part, dopamine receptors but have some effect on other types of receptors as well. For each neurotransmitter, the brain has different types of receptors, which aslo differ in behavioral functions. People differ in their amounts of each type of receptor. Some people have genes that change the shape and effectiveness of certain receptors. What this means is one person might have a large number of dopamine type D4 receptors and very few D1 or D2 receptors, where someone else has more D1, less D4, and a normal amount of D2 receptors. A drug that alters dopamine synapses can have different effects on different people.

Researchers in 1954 found that brain stimulation is reinforcing and almost completely and exclusively in tracts of axons that release dopamine. Dopamine has been known as a pleasure chemical. Addictive drugs have a very large ability to be over-bearing on the user's cravings.

Many extremely highly addictive drugs are stimulant drugs. These drugs produce alertness, mood elevation, excitement, lower fatigue, and usually give an increased motor activity. Each of these drugs increase the activity of the dopamine receptors.

Amphetamine produces dopamine synapses stimulation by increasing the release of dopamine from the presynaptic terminal. The presynaptic terminal usually reabsorbs released dopamine via a protein called the dopamine transporter. Amphetamine reverses the transporter, forcing the cell to excrete dopamine instead of absorbing it. Cocaine stops the reuptake of dopamine, serotonin, and norepinephrine, which lengthens the effects.

Research shows that the behavioral effects of cocaine are dependent on the increasing dopamine effects and also on serotonin effects. Since both Cocaine and damphetamine raise dopamine activity, their behavorial effects are quite similar.

The effects of amphetamine and Cocaine are intense but doesn't last long. By increasing the release of domapine or lowering its reuptake the drugs increase the buildup of dopamine in the synaptic cleft. However, the extra dopamine washes away from the synapse quicker than the presynaptic cell can synthesize more dopamine. Also the excess dopamine activates autoreceptors on the presynaptic terminal, giving a negative signal, which reduces further release of dopamine. The end result is that within a few hours of cocaine or amphetamine the user will fall into a depressed state that is well-known as "crashing".

Tolerance by the user also plays a role in the effects of the drug. After someone has used a drug repeatedly, the drug will release less dopamine and more of the transmitter called dynophin, wich counteracts the effects of the drug. This will result in increasing the frequency and dosage of the drug


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Conclusion:

Long term use of these types of drugs can cause long-term, permanent disruption of brain functions. Long-term cocaine use causes lasting changes in blood flow and metabolism in the brain, which greatly increases their chances of epilepsy, stroke, and memory functions.

Credits

Giros, Jaber, Jones, Wight-man`, & Caron, 1996

Rocha et al., 1998; Volkow, Wang, Fischman, et al., 1997

R.A. Harris, Brodie, & Dunwiddie, 1992; wise & Bozarth, 1987

Xu, Hu, cooper, White, & Tonegawa, 1996

London et al., 1990

Mattay et al., 1996

Gainetdinov et al., 1999\

McCann, Lowe, & Ricaurte, 1997

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    • ib radmasters profile image

      ib radmasters 4 years ago from Southern California

      Very interesting take on a complex subject.

      Do you have any idea how long it takes for the brain to recover from use of these drugs once they are stopped being taken. Of course, I am talking about occasional use rather than habitual. Just curious.

    • libby1970 profile image
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      libby1970 4 years ago from KY

      It depends on the severity of the damage! Some brains may never recover. Once neurons are destroyed they are gone forever! Some areas may improve over time, but it is very hard to say as every person is different and every user may have different side-effects and damage.

    • Rodric29 profile image

      Rodric Johnson 4 years ago from Phoenix, Arizona

      Nice hub. Drugs are very dangerous when used properly. Taking them for recreation is so terrible! Drugs affect us differently and effectively changes our lives whether those affects are permanent or not because of the experience. I had a family member who did hard drugs and the only thing that person lives with now is the fact that a bad choice was made.

      I have heard of others that have tried drugs once and it completely limits them. Our bodies produces different hormone levels and has different chemical quantities based on diet and exercise, environment, including but not limited to the housing, drive to work, food preparation smells, diet, you name it! We have to be aware or die. Good hub.

    • libby1970 profile image
      Author

      libby1970 4 years ago from KY

      Absolutely Rodric. People don't consider the consequences of their actions. It's a very dangerous game they play.

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      Paul 2 months ago

      There's only one God, one Savior, one baptism, and one Spirit that gives to all who believe His promises. God washed and purified me by the precious blood of Jesus Christ, and if you do not have faith then consider what your time is spent doing and realize the authority our God gave to His Son when He risen, because if one willfully chooses to have a selfish ambition to self-please and self-promote then according the Gospel of Jesus Christ which I believe in that person will perish in its evil deeds.

      6 [b]For after all it is only just [c]for God to repay with affliction those who afflict you, 7 and to give relief to you who are afflicted [d]and to us as well [e]when the Lord Jesus will be revealed from heaven with [f]His mighty angels in flaming fire, 8 dealing out retribution to those who do not know God and to those who do not obey the gospel of our Lord Jesus. 9 These will pay the penalty of eternal destruction, away from the presence of the Lord and from the glory of His power, 10 when He comes to be glorified [g]in His [h]saints on that day, and to be marveled at among all who have believed—for our testimony to you was believed. 11 To this end also we pray for you always, that our God will [i]count you worthy of your calling, and fulfill every desire for goodness and the work of faith with power, 12 so that the name of our Lord Jesus will be glorified in you, and you in Him, according to the grace of our God and the Lord Jesus Christ.

      2 Thessalonians 1:6-12

      (May my God give hope to the needy, poor, and sick through Jesus Christ His Son, who was crucified for the redemption of those who believe in Him)

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