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1. Define neurotransmitters and describe their role in neurotransmission. Discuss how they are released, how they affect receiving neurons, and how they are removed from receptor sites. 2. Pick one neurotransmitter and discuss the effect it has on our bodies. Also discuss the transmitter's connection with disease or disorders. 3. Once you have discussed a specific disease associated with neurotransmitter imbalance, describe the treatment options available as well as identify an individual associated with the disease. For example, Michael J. Fox's battle with Parkinson's disease. 4. Discuss the importance of biology for understanding behavior.
Pinel defines described neurotransmitters as the chemicals that act as signals between the cells in the brain. They are thought to be found in the brains of all living organisms. A technical definition are chemicals that communicate between two neurons or multiple nuerons by crossing synapses. Otto Lowewi, a German Pharmacologist was the first to show that there was a space or synspse between the cells and the cells were not passing current. His experiments conducted using frogs confirmed his hypothesis that chemicals communicated to a cell or nueron as to how it should respond. These neurotransmitters are also endgenous - they are chemicals that are produced from within.(1)
In understanding how these special chemicals are used to communicate they are classified as amino acids, peptides, and monoamines.(8-Ben Best) In a nutshell the only direct action of a neurotransmitter is to activate a receptor. A presynaptic cell stores them in vesicles and releases the chemical as molecules (i.e. a chiral molecule) where it migrates the synapse to bond to the receptors of a postsynaptic cell or else is quickly degraded. (7)
Amino acids are also called zwitterions. Amino Acids function as bonding agents and occur outside of cells hence their use as neurotransmitters. They can be both positive and negative. A very unique aspect of amino acids is that scientist examining meteorites and such - even earth stratification, look for evidence of life at its most basic level using amino acids. Why? The molecules formed by amino acids or chiral when synthetically formed (non living) always have a sterochemical preference and that is what has been found in meteorites so far. amino Acids found in living things do not, however have a "stereochemical preference". We often hear about carbon dating to determin the age of something but most of us are not familiar with the stereochemical preference.(10) (http://www.bmb.psu.edu/courses/bmb401H/Chapter4.pdf)
Peptides typically have larger molecules tend to modulate slower, ongoing brain functions. When reseachers consider neurotransmitters as peptides they are classified into three broad categories this way: small-molecule neurotransmitters, neuropeptides, and unconventional transmitters. Small-molecule transmitters are released when quicker reactions are needed. It is the more recent method of classification based on new chemicals discovered that meet the crieria established to be labeled a neurotransmitter. since the 1970s more than 100 polypeptide molecules have been identified. Research involving neuropeptides has linked them to many neurological diseases giving rise to the label of the "disease" neurotransmitter.
One such disease will be explored later in this paper. because they are lare peptides molecules consist as few as three amino acids and as many as 36 amino acids. Study of peptides has also revealed that just as a postsynaptic neuron can have different receptors a presynaptic neuron can have more than one type of vesicle and can release more than one kind of chemical at a time.
Regulatory Peptides as Disease Markers, Professor Gibor L. Kovics, Institute of Diagnostics and Management, University of Pcs and Central Laboratory, Markusovszky Teaching Hospital, Markusovszky St. 3.,H-9700 Szombathely Hungary(1)
Monoamines should also be called the mood neurotransmitter. It uses a single form of amino acids to create its molecule. Unlike Peptides, there are only six known monoamines and all six have an impact on mood. The six monoamine neurotransmitters include:(3) (5)
Dopamine, produced from phenylalanine and tyrosine
Norepinephrine or noradrenaline
Epinephrine or adrenaline
Serotonin, also known as 5-hydroxytryptamine, or 5HT
Histamine, produced from histidine
Before moving on to a specific neurotransmitter and a disorder associated with it, it should be pointed out that work in this area is quite new - as I pointed out most of the new neurotransmitters have been identified since 1970. So for historical purposes a look at the major discoveries in this area prior to 1970 is merited.
Acetylcholine was the first neurotransmitter to be discovered. It was isolated in 1921 by the German biologist, Otto Loewi, He won the Nobel Prize for his research. Acetylcholine is responsible for much of the stimulation of muscles, including the muscles of the gastro-intestinal system. It is also found in sensory neurons and in the autonomic nervous system. It plays a role in regulating REM (dream) sleep. A link between acetylcholine and Alzheimer's disease has been identified. President Ronald Reagan suffered from this disease before his death. A 90% loss of acetylcholine typically occurs in the brains of people suffering from Alzheimer's - a major cause of senility.
In 1946, a Swedish biologist, Ulf von Euler discovered norepinephrine (aka called noradrenalin). He also another Nobel Prize winner. Norepinephrine is strongly associated with bringing our nervous systems into "high alert." It is prevalent in the sympathetic nervous system. As a smaller molecule it can rapidly increase our heart rate and blood pressure. The adrenal glands produce it and releases it into the blood stream. In works in conjunction with its close cousin, epinephrine (aka adrenalin). It is also important for forming memories. Stress depletes adrenalin avialable, whereas exercising elevates it.
A second relative of norepinephrine and epinephrine is dopamine. It was also discovered by a Swede - Arvid Carlsson in the 1950s. Known as an inhibitory neurotransmitter, when it bonds with its receptor neurons, it blocks the tendency of that neuron to fire. Dopamine is strongly associated with reward mechanisms in the brain. Unfortunatly "feel good" chemicals interphere with it creating a desire to repeatedly use them. Some drugs, however that block dopamine can control schizophrenia. An opposite problem is that too little dopamine in the motor areas of the brain is responsible for Parkinson's disease severe muscle tremors. Arvid Carlsson received a Nobel Prize in 2000! He developed L-Dopa - a forerunner of dopamine that can alleviate some of Parkinson's effect.
In 1950 another inhibitory neurotransmitter was discovered. Eugene Roberts and J. Awapara discovered GABA (gamma aminobutyric acid). GABA acts like a brake to the excitatory neurotransmitters that lead to anxiety. It has a calming effect. So someone with low levels of GABA often suffer from anxiety disorders. Valium is supposed to enhancing GABA's effect. Like Dopamine, other drugs also influence the GABA receptors - alcohol and barbituates. Epilepsy is associated with too little GABA in certain areas of the brain.
Other significant discoveries include Glutamate (1900? - a cousin of GABA it wasn't formally isolated until 1994) SMG is used enhance the flavor in soups & chinese food. Serotonin was found in the blood stream. It plays a role in our perceptions so manipulating it with drugs can cause halucinations! We get back to the 1970s with Endorphin. It is short for "endogenous morphine." This drug reinforces the fact that they are produced within the body as it is related to a bear's hibernation cycle.
The neurotransmitter I selected to describe its effect on the body is dopamine. It has been briefly mentioned as an inhibitory neurotransmitter as well as its link to both Schizophrenia and Parkinsin's Desease. Dopamine is in the classification of one of the six monoamines. This chemical substance has only one amino acid group. They are in the group called catechola- mines. The monoamines are dependent on proteins called monoamine transporters. The most obvious impact of a disruption to this system results in mood swings.It is essential for balance and smoothness of movements.(4) The dynamics ot too much, too little, and too many molecules attaching to D2 receptors and in different areas of the brain, etc. has added to the complexity of developing drugs that will stabilize it as needed. Research is far from where scientists can confidently predict absolutely a drug's effectiveness relative to a neurochemical profile.(3) But dopamine is currently in vogue in research circles. On top of that Dopamine seems to interact with other neurotransmitters in a sort of teeter-totter manner. (http://www.iscid.org/encyclopedia/Monoamine_Neurotransmitters)
A disease associated with Dopamine, which is not a familiar term with the general public, is Tourette Syndrome. In layperson's vernacular it is a disorder involving "tics". It is considered to be an autosomal dominant disorder, but a gene attributed to it has not been isolated. It appears to be a trait passed on in subsequent generations, but Tourette Syndrome can only be diagnosed based on observation.(2)(http://www.answers.com/topic/tourette-s-syndrome)Most persons who live with this disease are quite stable after a good nights sleep and when there are no stressful situations. As the day goes on and an individual with the disease grows tired the tics become very noticeable. When a family with an adult and children with this condition are getting ready for bed interactions are dominated by the tics. Imagine brushing your teeth and performing simple mundane activities that other people take for granted. And unexpected or perceived stessful situations bring on the tics. For example, going on a blind date, would set off the tics at the least desired moment. Prior it was pointed out that Dopamine is affiliated with smoothness of movement. Some persons have found that diet influences the condition. Certain patterns have been identified with the condition, but efforts to alleviate the pattern have not met scientific rigor. Research is confronted with ethical issues. Pharmacological methods are the second type of non-invasive tools to study the brain. A drawback can be the medications used. Medicines referred to as antagonists and agonists are given to the patient.The specific drug used is is to either increase or reduce the effects of neurotransmitters. Cocaine is an example of an agonist. When it is present in the brain it prevents the effects of dopamine and norepinephrine from being repressed. A side effet is insomnia and others can occur. Botox works as an antagonist. (6)We are familiar with its use in cosmetic surgery. In small does it prevents wrinkles. In studies Botox is used as a neurotoxin and "it blocks the release of acetylcholine at neuromuscular junctions". This can make it dangerous so it has to be carefully administered in very small amounts.(1) (Pinel, 2007, p 88).
The Movie Matchstick Men, starring, Nicholas Cage, presented a stereotype concerning the disease. The stereotype is that while he was under stress due to his illicit behavior - scams he was running, his tics were worse. When he ended his criminal ways and settled for a regular life his tics miraculously ended. Perhaps the most famous person to cope with Tourette Syndrome is Armadeus Mozart - the great composer. Another modern day composer, Robert Gore-Langton also suffers from Torette Syndrom. He believes that the kind of mental activity that composing requires is actually a way Mozart medicated himself. When Mozart was not composing, besides (motor) Tics he was prone to filthy verse and breaking wind.(9)
An over reliance on observation can mask underlying causes of various behaviors, whether normal or abnormal. A foundation in biology is in valuable to a therapist so she has a proper perspective when working with a client .An appreciation of the complexity of the human brain is gained by learning about neurons, synaps, glands and the chemicals-neuro transmitters. When making a laundry list of her client's behaviors - drinking, medications, etc. can provide insights into behavior. Certain tests, such as those involving memory, for example, could help the therapist realize a problem with a neurotransmitter and which type. An appreciation of biology will minimize stereotypes, rigid thinking, and lead to better judgements and more effective treatment for a client.
(1)Pinel, J. P. J. (2007). Basics of biopsychology. Boston, MA: Allyn and BaconGeneral Psychology, Neurotransmitters, Dr. C. George Boeree
(4)Article source: TCPR, July 2006, Vol 4, Issue 7, Neruotransmitters in Psychiatryhttp://thecarlatreport.com/article/dopamine-getting-reaquainted
(8)Ben Best, http://www.benbest.com/science/anatmind/anatmd10.html
(9)Robert Gore-Langton, 13 October 2004, I Know What Made Mozart Tic,http://www.telegraph.co.uk/culture/music/3625399/I-know-what-made-Mozart-tic.html
Edited by Timothy the Teacher on 4/2/2010 at 7:57 AM EST