Bio-science Example

Bio-science Example Bio-science â€" Essay Example > Bio-science1. Drugs which act on serotonin receptors are important for managing both migraines, mood disorders (e. g. antipsychotic) and vomiting: a. For each of these conditions name one drug (using generic drug names)which is used in Australia and acts via serotinergic receptors. b. Explain the mechanism of action of each drug (i. e. how does it work? ). c. What is serotonin syndrome and why might ecstasy cause symptoms of serotonin syndrome? 1. a. The triptans act via serotinergic receptors as they are 5-HT1B/1D agonists targeting the trigeminovascular system. Sumatriptan is a triptan used in the management of migraine (Spierings del Rio, 2002). A class of drugs used in the treatment of mood disorders, which act via the serotinergic receptors are the selective serotonin reuptake inhibitors or serotonin specific reuptake inhibitors (SSRIs). Citalopram is an SSRI used in the management of mood disorders (Rollema Sprouse, 2005). The 5-HT3-receptor agonists are a class of drugs u sed in the management of vomiting, as they are capable of blocking the 5-HT-3 receptor sites efficiently. Ondansetron is a 5-HT3-receptor agonist used in the management of migraine (Husband Worsley, 2007). 1.b. Many of the triptans that are in current use for the management of migraine have selective serotonin receptor agonist activity. This action of the triptans causes constriction in the arteriovenous anastomes. Thus it is posited that the triptans ability to control migraine is based on this constriction of the arteriovenous anastomes. Sumatriptan brings about constriction in the superficial temporal artery. In addition Triptans like sumitriptan have demonstrated the capability to inhibit the release of calcitonin gene-related peptide, which is responsible for the mediation of the vasodilation element of neurogenic inflammation (Spierings del Rio, 2002). In essence the mode of action of the SSRIs can be taken as making more serotonin available in the extracellular environmen t, by inhibiting the reuptake of serotonin by the presynaptic cell. This enhanced extracellular level of serotonin makes for higher levels of serotonin to bind with the postsynaptic receptor (Rollema Sprouse, 2005). The mechanism involved in vomiting consists of the formation of local free radicals as a result of cytotoxic agents or other substances that are potentially toxic. These free radicals bring about the release of 5-HT from the enterochromaffin cells in the GI tract. 5-HT is the stimulus for the 5-HT3 receptors present on the adjacent vagal afferent neurons to cause a vigorous vomiting response. 5-HT3- receptor agonists, like ondansetron, block the 5-HT3 receptors in the GI tract, the chemoreceptor trigger zone, and the nucleus tractus solitarius efficiently, to inhibit the vomiting response triggered by the 5-HT3 receptors. (Husband Worsley, 2007). 1.c. Birmes et al 2003, p. 1439 define serotonin syndrome as “the result of over stimulation of 5-HT1A receptors by selec tive serotonin reuptake inhibitors (SSRIs), tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOI) or other serotonergic agents”. Serotonin syndrome can occur to any individual irrespective of age or sex triggered by an overdose of a serotonergic agent, and occurs within the time interval of twenty-four hours from the overdose event. The three features of mental, autonomic and neurological disorders characterize serotonin syndrome. Serotonin is life threatening, but normally serotonin syndrome is not fatal, when effectively managed (Birmes et al 2003).