Resposta RESPOSTA 1 A serotonina ou 5-hidroxitriptamina (5-HT) é um neurotransmissor presente em várias áreas do sistema nervoso central. Regula uma multiplicidade de funções as mais importantes das quais estão relacionadas com a depressão. Em regra os indivíduos deprimidos têm níveis baixos de serotonina no sistema nervoso central. Para obviar a esta situação administram-se inibidores da recaptação da serotonina pelos neurónios, como seja o caso de medicamentos como fluxetina ou PROZAC, como é conhecido comercialmente. Um certo número de alimentos, como bananas, tomate, são ricos no precursor da serotonina, o triptofano. Sem este precursor não é possível sintetizar serotonina suficiente para as suas várias funções. RESPOSTA 2 A serotonina, também chamada 5-hidroxitriptamina é um neurotransmissor (substância envolvida na comunicação de informação entre células nervosas ou entre células nervosas e células efectoras). Também existe em algumas células não nervosas (incluindo alguns tumores intestinais). É fabricada, no nosso organismo, a partir do triptofano (um amino-ácido). Tem funções de controlo da motilidade e secreção gastrointestinal. No sistema nervoso central está envolvida no controlo do estado de sono ou vigília, consciência, agressividade e humor. Por isso algumas perturbações destes sistemas (por exemplo ansiedade, depressão), podem ser tratadas com medicamentos que interferem com os sistemas da serotonina. RESPOSTA 3 A serotonina é, quimicamente, a 5-hidroxitriptamina. É sintetizada a partir do amino-ácido triptofano, por hidroxilação no anel aromático e descarboxilação, sucessivas. É um mediador do sistema nervoso, abundante em certas áreas como o hipotálamo. Exibe funções vasoconstritoras. RESPOSTA 4 A serotonina é um neurotransmissor, isto é uma molécula envolvida na comunicação entre as células do nosso cérebro (neurónios). Esta comunicação é fundamental para a nossa percepção e avaliação do meio que nos rodeia, e para a nossa capacidade de resposta aos estímulos ambientais. Apesar de serem poucos os neurónios no nosso cérebro com capacidade para produzir e libertar serotonina, existe um grande número de células que detectam esse neurotransmissor. Desse modo, a serotonina desempenha um importante papel no funcionamento do nosso sistema nervoso e existem numerosas patologias relacionadas com alterações na actividade deste neurotransmissor. A serotonina parece ter funções tão diversas como o controlo da libertação de algumas hormonas e a regulação do ritmo circadiano, do sono e do apetite, entre outras. Diversos fármacos que controlam a acção da serotonina como neurotransmissor são actualmente utilizados, ou estão a ser ensaiados, em patologias como a ansiedade, depressão, obesidade, enxaqueca e esquizofrenia, entre outras. Drogas como o "ecstasy" e o LSD mimetizam alguns dos efeitos da serotonina em algumas células alvo. RESPOSTA 5 For most people who are not in touch with science, the word serotonin is virtually unknown to them. If they have heard of serotonin, they probably associate it with depression or as a term used in one of their past psychology courses. Serotonin is involved in the state of depression, but it is also involved in human behavior, appetite, hunger, the cardiovascular system, and most notably, the central nervous system. Without the natural chemical serotonin, messages from the brain would not be properly transmitted throughout the nervous system. This basically means that without normal levels of serotonin, the simple acts of eating, sleeping, living, and walking could not occur normally. The year 1948 marked the first time that serotonin was isolated in blood. Since it was isolated in blood serum, the name serotonin came about (Woolley, 1962). Serotonin is a neurotransmitter which helps relay information throughout the nervous system. Serotonin is stored in the nerve cells where it sits until the brain relays a message. The nerve cell then releases the serotonin into the space between it and the next nerve cell. Acting as a bridge, the serotonin carry the message across to the next cell (OCD Resource Center, 1997). After the information has been relayed, the serotonin returns to the nerve cell until the next message comes along. Serotonin is found in three major areas of the human body: blood vessels, the central nervous system, and in the intestinal wall. Serotonin is also believed to be related to mood, appetite, and emotion. According to Dr. P.J. Cowen of the University of Oxford, serotonin is the controller of mood and the vital functions of the brain (Cowen, 1998). It is essential that the human body has a normal level of serotonin between the nerve cells and in the brain. When serotonin levels are lower than normal, people may suffer from depression or other psychological and physical problems. There seems to be a relationship between low levels of serotonin and depression. People with low levels of serotonin usually suffer from depression. Likewise, patients who suffer from Obsessive Compulsive Disorder (OCD), also show lower than normal levels of serotonin between nerve cells (OCD Resource Center, 1997). OCD patients are characterized as overly compulsive, very obsessive, and have tremendous anxiety. Low levels of serotonin are also involved in the acts of aggression, such as violent crimes or even suicide (CSU, Chico Department of Psychology, 1997). However, scientists are contiuing to search for a definite correlation between low levels of serotonin and suicide. For example, scientists have conducted experiments on monkeys to observe the effects that low levels of serotonin would have on them. The results showed that the monkeys with lower than normal serotonin levels acted more aggressively and had a tendency towards risky behavior. Lower than normal levels of serotonin may also be associated with the control of hunger and appetite (CSU, Chico Department of Psychology, 1997). For the treatment of obesity, drugs are taken to increase the level of serotonin in the brain, helping to reduce appetite. The drugs used to treat obesity include fenfluramine/Pondimin and dexfenfluramine/Redux. In recent years the anti-obesity Œfen-phen,' was developed in order to increase serotonin levels. On the downside, some users of the drug ultimately died. According to the International Coalition for Drug Awareness and a Massachussetts Institue of Technology press release, "too much serotonin damages blood vessels in lungs, and can harm heart valves" (MIT Press Release, 1998). To treat depression, drugs such as Prozac, Zoloft, and Paxil are used to block the reuptake of serotonin in the axon terminals to keep sufficent levels of serotnin between nerve cells. Although increasing serotonin by artificial means has proven at times to be unhealthful, serotonin levels may be increased by natural means. Tryptophan, an amino acid which is found in the blood stream, can help increase sertonin levels (Cowen, 1998). Foods such as walnuts, pineapple, turkey, chicken, yogurt, and bananas contain large amounts of tryptophan. By incorporating these foods into a normal diet, serotonin levels may increase to normal levels. Also, by combining these foods with carbohydrates such as pastas, the brain is able to absorb tryptophan more effectively, which plays a key role in deciding how much serotonin will be produced in the brain. 2. Serotonin is one of a group of chemical messengers known as neurotransmitters that carry out communication in the brain and body. The message molecules flow from a nerve cell or neuron onto other neurons that act as receivers. There, they attach to a distinctly shaped area on the neuron called a receptor site. This union, which is like a key fitting into a lock, triggers signals that either allow the message to be passed on to other cells or prevent the message from being forwarded. Since the discovery of serotonin in the 1950s, researchers are finding evidence that one of its roles is to mediate emotions and judgment. For example, in animal studies, scientists discovered that low serotonin levels may be associated with impulsive or risky behavior. Researchers observed monkeys and found that the ones who took more dangerous leaps traveling from tree to tree had lower serotonin levels and more injuries from falling. Other scientists examined rats and found the ones with low serotonin levels chose a small immediate reward instead of waiting for a bigger prize. Scientists also have compiled studies that show serotonin is implicated in aggressive acts. One example involves mice who lack one type of receptor that responds to serotonin. These defective mice attack intruders faster and more intensely. Other researchers examined the spinal fluid of murderers in Finland. Their results indicate that these individuals have abnormally low levels of serotonin. Some researchers now believe that suicide may be the ultimate act of inwardly directed impulsive aggression. In one new area of research, scientists are examining humans with brain imaging techniques and believe defects in serotonin processing are partially responsible for suicidal behavior. Preliminary results show that depressed people who have attempted suicide exhibit lower serotonin activity (see brain images) in response to a drug that boosts the amount of the chemical in the brain. In addition, the depressed had a history of comitting impulsive acts including overeating and aggressive behaviors such as lighting fires or fighting. Scientists plan to uncover the brain areas where serotonin's inactivity causes the most havoc and identify all the components that play a role in the defective processing. Researchers view the brain in action with a special imaging technique called positron emission tomography (pet). These pet scans compare the brain activity of a severely depressed patient (left) to a healthy volunteer (right). Both people received a drug called fenfluramine that is known to increase the availability of serotonin in the brain. The scans demonstrate that only the healthy patient has an increase in serotonin activity, which is represented by the orange and yellow shading. This suggests that the severely depressed have a very blunted response to the neurotransmitter or very low serotonin levels. Researchers plan to use the technology to devise imaging guidelines that would identify patients with this deficiency.