EFFECTS OF ALCOHOL AND AMPHETAMINES ON SYNAPTIC TRANSMISSION
Neurons, which are specialized cells, make up the nervous system. (Williams College Neuroscience, 1998) These nerve cells are specialized for receiving, processing and transmitting signals. (Sumanas, Inc., 2004) Accordingly, an efficient communication between these specialized cells is essential for the normal functioning of the central and peripheral nervous systems. (Williams College Neuroscience, 1998) This process by which information from a neuron to a target (neuron, muscle or secretory cell) across a specialized junctions called synapses is called synaptic transmission. (Gene Ontology Browser, 2004).
On the other hand, it is also known that drugs of abuse, such amphetamines, and alcohol can have various effects on the body functions of a human being. What happens, then, to the process of synaptic transmission when a person consumes alcohol or amphetamines?
Accordingly, drugs of abuse and many other kinds of experiences share the ability to alter morphology of neuronal dendrites and spines, which are the primary site of excitatory synapses in the brain. (Kolb et al, 2003) In fact, stimulants mimic the stimulation provided by the sympathetic nervous system. (Kimball, 2003) Amphetamine, one of the most widely used stimulant, block transporters used for the reuptake of dopamine (and noradrenaline) into presynaptic neuron, which causes the level of dopamine to rise in the synapses, and these high levels of dopamine in an area of the brain called the nucleus accumbens appear to mediate the pleasurable effects associated with amphetamine. (Kimball, 2003)
Although, amphetamines are also used medically; they are used to help people lose weight because they can suppress appetite, and also, it is used to help children with attention deficit/hyperactive disorder (ADHD). (Kimball, 2003) It was discovered that hyperactive children exhibit a behaviour that is caused by the slow working of their brains. (Myron, 2003) Children with ADHD usually could not concentrate because the world moves too fast for them, and the amphetamine Ritalin allows these children’s synapses to fire more quickly so they can keep up with their environment and be able to focus on their work more effectively and proficiently. (Myron, 2003)
On the other hand, alcohol appears to have two general effects on the membrane, anxiolytic and anesthetic, which are due to the interaction of ethanol with the membranes and membrane proteins. (Palmer, 1991) Due to ethanol, there is greater fluidity in cellular membranes, which in turn increases the permeability of that membrane to other chemical signals. (Wayne State University, 2003) “In the case of neurons, these chemical signals, which are used in conjunction with concentration gradients, must be kept either inside or outside the cell to allow for synapses to occur. When the chemical signals leak in/out due to the increased permeability of the membrane, the speed of the synapse is reduced.” (Wayne State University, 2003)
In addition, a study conducted by Gruol et al (2000) found out that: “alcohol effects on dendritic function could lead to prominent alterations in synaptic responses, including a disruption of calcium regulation of neuronal biochemistry and excitability, and may lead to neuronal death due to the toxic effects of calcium. Such actions of alcohol could contribute to the known toxic effects of alcohol on the developing nervous system. Moreover, because AMPA receptors mediate most fast synaptic transmission in the brain, many parts of the brain could be affected by this action of alcohol.”
References:
Gene Ontology Browser. Synaptic Transmission. In Mouse Genome Informatics. Available at: [http://www.informatics.jax.org/searches/GO.cgi?id=GO:0007274]. Accessed: [27/01/04].
Gruol et al. (2000). Molecular Mechanisms of Neuronal Signaling and Pathologic Changes. In The Scripps Research Institute (TSRI) Scientific Report. California: TSRI.
Kimball, John W. (2003). Drugs and the Nervous System. In Kimball’s Biology Pages. Available at: [http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/D/Drugs.html]. Accessed: [27/01/04].
Kolb B, Gorny G, Li Y, Samaha A.N., and Robinson T.E. (2003). Amphetamine or cocaine limits the ability of later experience to promote structural plasticity in the neocortex and nucleus accumbens. In Proceedings of the National Academy of Science (PNAS) of the U.S.A., 100(18): 10523-8.
Myron, Harold (ed). (2003). Effects of Amphetamines (Rilatin). In Newton, BBS. Chicago: University of Chicago, Argonne National Laboratory.
Palmer, Norman T., ed. The Molecular Pathology of Alcoholism. New York: Oxford University Press, 1991. pp. 238-242.
Sumanas, Inc. (1994). Synaptic Transmission Sumanas, Inc. Available at: [http://www.sumanasinc.com/webcontent/anisamples/neurobiology/synaptictransmission.html]. Accessed: [27/01/04].
Wayne State University. 2003. Effects of Alcohol on the CNS. Detroit: College of Science, Wayne State University.
Williams College Neuroscience. (1998) Synaptic Transmission: A Four Step Process. Massachusetts: Williams College.
Credit:ivythesis.typepad.com
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