Activation, of monoamine oxidase

The TCAs, such as amitriptyline (Elavil) and dox-epin (Sinequan), inhibit reuptake of norepinephrine or serotonin at the presynaptic neuron. Drug classified as MAOIs inhibit the activity of monoamine oxidase a complex enzyme system that is responsible for breaking down amines. This results in an increase in endogenous epinephrine, norepinephrine and serotonin in the nervous system. An increase in these neurohormones results in stimulation of the CNS. The action of the SSRIs is linked to their inhibition of CNS neuronal uptake of serotonin (a CNS neurotransmitter). The increase in serotonin levels is thought to act as a stimulant to reverse depression. 

Perez, N. M. Benedito, M. A. (1997). Activities of monoamine oxidase (MAO) A and B in discrete regions of rat brain after rapid eye movement (REM) sleep deprivation. Pharmacol. Biochem. Behan. 58, 605-8. 

Cassel GE, Persson S-A, Stenstrom A. 1994. Effects of cyanide in vitro and the activity of monoamine oxidase in striatal tissue from rat and pig. Biochem Pharmacol 47(3) 499-504. 

Dextromethorphan hydrobromide is the D-isomer of levorphanol. It lacks CNS activity but acts at the cough center in the medulla to produce an antitussive effect. It is half as potent as codeine as an antitussive. Anecdotal reports of abuse exist, but studies of abuse potential are lacking. It has few side effects but does potentiate the activity of monoamine oxidase inhibitors, leading to hypotension and infrequently coma. Dextromethorphan is often combined in lozenges with the local anesthetic benzocaine, which blocks pain from throat irritation due to coughing. 

Mechanism of Action An antiparkinson agent that irreversibly inhibits the activity of monoamine oxidase type B, the enzyme that breaks down dopamine, thereby increasing dopaminergic action. Therapeutic Effect Relieves signs and symptoms of Parkinson s disease. 

Adler LE, Hoffer LD, Wiser A, et al Normalization of auditory physiology by cigarette smoking in schizophrenic patients. Am J Psychiatry 150 1856-1861, 1993 Adolfsson R, Gottfries GG, Oreland L, et al Reduced levels of catecholamines in the brain and increased activity of monoamine oxidase in platelets in Alzheimer s disease therapeutic implications, in Alzheimer s Disease Senile Dementia and Related Disorders [Ageing, Vol 7). Edited by Katzman R, Terry RD, Bick KL. New York, Raven, 1978, pp 441-451... 

Luine VN, Khylchevskaya RJ, McEwen BS Effect of gonadal steroids on activities of monoamine oxidase and chohne acetylase in rat brain. Brain Res 86 293-306, 1975... 

The frequent occurrence of sialylated enzymes, or even of multiple forms, which are sometimes tissue-dependent, with a varying number of sialyl residues as, for example, in y-glutamyltranspeptida.se (EC 2.3.2.2),456,457 is not yet fully understood. Although the activity of most of these enzymes is not influenced by removal of sialic acid,454 the activity of monoamine oxidase A (EC 1.4.3.4) of outer mitochondrial membranes of rat liver has been shown to be destroyed by treatment with sialidase438 the substrate specificity of acetylcholinesterase (EC 3.1.1.7) is altered,459 the kinetic properties of human acid and alkaline phosphatases (EC 3.1.3.1 and 3.1.3.2) are changed, and the stability of a-D-galactosidase (EC 3.2.1.22) is drastically lowered.415 In these cases, an influence of sialyl residues on the conformation of the enzyme is assumed, but awaits firm evidence. 

Norepinephrine and epinephrine can be metabolized by several enzymes, as shown in Figure 6-6. Because of the high activity of monoamine oxidase in the mitochondria of the nerve terminal, there is significant turnover of norepinephrine even in the resting terminal. Since the metabolic products are excreted in the urine, an estimate of catecholamine turnover can be obtained from laboratory analysis of total metabolites (sometimes... 

If schizophrenia results from an elevated dopamine content of the brain, the fault may lie with either an oversupply or a reduced rate of metabolism of dopamine. The possibilities of reduced activity of monoamine oxidase or of dopamine (i-hydroxylase have both been suggested. The plasma level of the dopamine metabolite homovanillic acid (Fig. 30-26) is elevated in schizophrenia and is correlated with the... 

C. MAOIs reduce the activity of monoamine oxidase in breaking down presynaptic amines (leaving more available for release into the presynaptic cleft). 

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