Receptor affinity antidepressant drugs

Serotonin mediates many central and peripheral physiological functions, including contraction of smooth muscle, vasoconstriction, food intake, sleep, pain perception, and memory, a consequence of it acting on several distinct receptor types. Although 5-HT may be metabolized by monoamine oxidase, platelets and neurons possess a high-affinity mechanism for reuptake of 5-HT. This mechanism may be inhibited by the widely prescribed antidepressant drugs termed selective serotonin re-uptake inhibitors (SSRl), e.g. fluoxetine (Prozac ), thereby increasing levels of 5-HT in the central nervous system. 

It is probably relevant that the antidepressant drugs with a high affinity for alpha-adrenergic receptors are associated with weight gain, whereas those with a lower affinity, such as serotonin reuptake inhibitors (SSRI), are not (Virk et al. 2004). 

Table 8.6 Affinities of Antidepressant Drugs for Human Monoamine Receptors"... 

The neurochemical effects of the tricyclic antidepressants are blockade of the re-uptake of norepinephrine and for some drugs also serotonin by nerve terminals in the CNS and peripherally. This reuptake inhibition results in higher concentrations of the neurotransmitters at their receptors sites. There is little or no effect on DA neurotransmission. The tricyclic antidepressants have varying affinities for U2... 

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