Serotonin chemical structure

Figure 20.5 The chemical structure of the selective serotonin reuptake inhibitors (SSRIs)...

Fig. 31. Example of neuroactive indole alkaloids from plants. Note the similitude of chemical structure of harmine, harmaline, and serotonin.

FIGURE 13-1 Chemical structure of 5-hydroxytryptamine (5-HT serotonin) and related indolealkylamines. The indole ring structure consists of the benzene ring and the attached five-member ring containing nitrogen. 

The chemical structure of histamine has similarities to the structures of other biogenic amines, but important differences also exist. Chemically, histamine is 2-(4-imidazolyl)ethylamine (Fig. 14-1). The ethylamine backbone is a common feature of many of the amine transmitters (e.g. dopamine, norepinephrine and serotonin). However, the imidazole nucleus, absent from other known transmitters, endows histamine with several distinct chemical properties. Among these is prototypic tautomerism, a property that permits it to exist in two different chemical forms (Fig. 14-1). The tautomeric properties of histamine are thought to be critical in the... 

Pharmacoiogy Nefazodone is an antidepressant with a chemical structure unrelated to available antidepressant agents. The mechanism of action is unknown. Nefazodone inhibits neuronal uptake of serotonin and norepinephrine. Pharmacokinetics ... 

TCAs derive their name from their chemical structure aU tricyclics have a three-ring nucleus. Currently, most clinicians are moving away from using TCAs as first-line drugs relative to the newer antidepressants, they tend to have more side effects, to require gradual titration to achieve an adequate antidepressant dose, and to be lethal in overdose. Some data suggest that TCAs may be more effective than SSRIs in the treatment of major depression with melancholic features (Danish University Antidepressant Group 1990 Perry 1996) however, many skilled clinicians and researchers continue to prefer the newer antidepressants, even for patients with melancholia, for the aforementioned reasons. Newer medications that affect both norepinephrine and serotonin (e.g., venlafaxine and mirtazapine) also may have superior efficacy in severely iU depressed patients or when remission is defined as the outcome (Thase et al. 2001). 

Unlike reserpine, chlorpromazine has neither a serotonin-like chemical structure nor does it release serotonin from nerve raidings. 

Amoxapine has been found to be effective in several double-blind studies (Table 7-4 and Table 7-6). It is a dibenzoxazepine derivative that has both NE and serotonin uptake inhibiting properties. Amoxapine is converted into 8-hydroxyamoxapine, which has considerable dopamine receptor binding properties (i.e., radioreceptor bioassays on patients given amoxapine have found activity levels similar to those of patients on typical antipsychotics), a chemical structure similar to loxapine, and effects similar to antipsychotics (1Q3). As a result of this metabolite, amoxapine theoretically may have unique beneficial effects in psychotically depressed patients. However, this possibility has never been adequately tested. Nevertheless, this metabolite is likely responsible for some of the antidopamine effects reported in patients taking amoxapine, including acute and chronic extrapyramidal side effects and elevated prolactin levels ( 104). Like TCAs, amoxapine can be lethal in... 

Chemical structure of serotonin the 5-HT3 antagonists ondansetron, granisetron, dolasetron, and alosetron and the 5-HT4 partial agonist tegaserod. 

Clozapine is considered to be the prototype of the atypical antipsychotics, as it was the first to be recognized as having few if any extrapyramidal side effects, not causing tardive dyskinesia, and not elevating prolactin. Clozapine is one of five antipsychotics with somewhat related chemical structures (Fig. 11-36). Although certainly a serotonin 2A-dopamine 2 antagonist, clozapine also has one of the most complex... 

Clomipramine has also aroused interest because of an action on prolactin release, which occurs with major tranquillizers but not with other tricyclic antidepressants (289). This action of clomipramine is related to its chemical structure and reflects a greater effect on dopamine metabolism and serotonin uptake compared with other antidepressants. 

Psilocybin is a naturally occurring hallucinogen. It exerts neurotoxic effects similar to LSD and has a chemical structure similar to the neurotransmitter serotonin in the human brain. Psilocybin is found as an indole alkaloid (nitrogen-containing organic base) in the fungal (Protista) kingdom. Often it is accompanied by the related alkaloids, psilocin, baeocystin, and norbaeocystin. 

Cyproheptadine resembles the phenothiazine antihistaminic agents in chemical structure and has potent Hi receptor-blocking as well as 5-HT2-blocking actions. The actions of cyproheptadine are predictable from its Hi histamine and serotonin receptor affinities. It prevents the smooth muscle effects of both amines but has no effect on the gastric secretion stimulated by histamine. It has significant antimuscarinic effects and causes sedation. 

Antidepressants generally fall into one of three categories (1) tricyclic antidepressants (TCAs), which are so named because of their three-ring chemical structure (2) selective serotonin reuptake inhibitors (SSRIs), which block only the reabsorption of serotonin and not of norepinephrine and (3) monoamine oxidase (MAO) inhibitors, which inhibit the metabolic breakdown of norepinephrine and/or serotonin. 

This compound-cluster exhibits an extra ring attached to its basic indolic chemical structure. The resulting three-ring /3-carboline system has an unusually placed methoxy (CH3O) group, "in marked contrast to the orientation found in serotonin and the related tryptamines (Shulgin). 

Talopram 58 and citalopram 59 (Figure 2.17) are closely related in their chemical structures. Nevertheless, talopram is a norepinephrine uptake blocker with a selectivity factor of about 550 against serotonin uptake, whereas citalopram is a serotonin uptake blocker, with a selectivity of 3400 against norepinephrine uptake. A similar selectivity difference applies to the even more closely related pair nisoxetine 60, with a norepinephrine uptake selectivity of about 180, and fluoxetine 61 (Figure 2.17), with a serotonin uptake selectivity of 54 [33],... 

Monoamine oxidases (MAO-A and MAO-B) are mitochondrial enzymes that oxidatively deaminate endogenous biogenic amine neurotransmitters such as dopamine, serotonin, norepinephrine, and epinephrine. MAOs are like EMOs in that they catalyze the oxidation of drugs to produce drug metabolites that are identical in chemical structures to those formed by CYPs. Because the resulting structures are... 

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