The Effects of Drugs on Synaptic Transmission

According to recent research, the following drugs of abuse studied that may cause effects on synaptic transmission are:



Alcohol inhibits neurotransmission in two ways. First, it inhibits the excitatory channels on the postsynaptic neuron. Next, it lowers the rate of action potentials from the presynaptic neuron.  



At synapses where adenosine is the primary neurotransmitter, a high postsynaptic firing rate leads to sleepiness. Caffeine inhibits sleepiness by inhibiting adenosine neurotransmission. 



Nicotine affects neurotransmission by causing more action potentials in the presynaptic neuron and by causing more dopamine to be released per vesicle.   



Cocaine provides a sense of euphoria by blocking the reuptake of dopamine by the presynaptic neuron. This leads to a higher dopamine concentration in the synapse and more postsynaptic firing.



The mechanism by which heroin affects neurotransmission is unclear, but it is thought to increase the rate of vesicle fusion in the presynaptic neurons that use dopamine as a neurotransmitter.    

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Tags: Drugs, Neurotransmission, Research, Synaptic


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Comment by MARCOS FLEURY on July 19, 2011 at 7:16pm
Antidepressants have various effects on the body, including action at the neuronal synapses of the brain; the two most important of these effects are blockade of the reuptake of neurotransmitters, including NE, 5-HT, and dopamine, and blockade of certain neurotransmitter receptors. Currently available antidepressants may be classified as inhibitors of monoamine oxidase or as blockers of biogenic amine neurotransmitter reuptake, the latter best describing tricyclic antidepressants and selective 5-HT-reuptake inhibitors, because they block the reuptake of one or more neurotransmitters. However, recently introduced antidepressants, such as the 5-HT-NE-reuptake inhibitors, have synaptic effects that differ from those of older compounds. These synaptic effects are important in explaining certain side effects and drug-drug interactions associated with all classes of antidepresants. Catecholamines, especially norepinephrine (NE) and serotonin (5-hydroxytryptamine [5-HT]), have been implicated in the pathophysiology of depression. However, their exact roles and their interrelationship are not completely understood.

The antipsychotic drugs have been shown to act as inverse agonists at D2 and D3 dopamine receptors, and this property may be important for the antipsychotic effects of the drugs. It is suggested that the property of inverse agonism leads to a receptor up-regulation upon prolonged treatment, and this alters the properties of dopamine synapses. Several variants of the dopamine receptors exist with different DNA sequences and in some cases different amino acid sequences. These variants may have different properties that alter the effects of dopamine and the antipsychotic drugs. The determination of such variants in patients may help in the prediction of drug responsiveness.
Comment by libramoon on July 18, 2011 at 2:48pm
What about the anti-depressants and anti-psychotics?

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