serotonin drugs

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<TD vAlign=center> Serotonin is an inhibitory neurotransmitter which complements excitatory sympathetic systems like adrenaline and dopamine in the CNS. Like the "fight or flight" adrenaline compounds, serotonin is released not only at specific synaptic sites, but also in a broadcast manner into brain tissue from sets of "diffuse" neurons emanating from the emotional centers in the limbic system into the frontal lobe. This diffuse release sets the biochemical tone of large areas of neural functioning, controlling mood and motivation. Serotonin's inhibitory action is however more complex and selective than that of GABA sedatives like Valium or Xanax, which act more globally. Because of their effects on mood, serotonin-active drugs are used as antidepressants and anxiolytics (anti-anxiety) drugs.
High levels of serotonin are present in dominant members of animal societies, i.e. alpha males. CNS serotonin systems probably developed in concert with dopaminergic projections during primate evolution, which involved complex social hierarchies and a need to temper fight-or-flight impulses with increasingly complex cognitive and sensory mentation. It would be interesting to see if dolphins, for example, which have comparable (slightly larger) brain to body weight ratios as humans, have serotonergic systems of comparable development, since they "missed out" on the dominance drama of primate evolution.</TD></TR></T></TABLE></CENTER>
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serotonin antagonists


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<TD vAlign=center height=42> Ondansetron is a selective 5-HT3 antagonist. This receptor subtype is found on cholinergic neurons; when it is activated it inhibits release of acetylcholine. Along with its chemical relatives such as granisetron and zatosetron, it may thus be useful in reviving memory function in the aged. Granisetron is also used as an antiemetic (Kytril) in chemotherapy.
Ketanserin, a selective 5-HT2 antagonist, also acts on alpha-1 adrenoceptors to lower blood pressure. Mescaline, a hallucinogen, antagonizes 5-HT2 terminals and has been tried as an alternative to dopamine blocking antipsychotics (without much success; it facilitates dopamine function). Oxetorone is a relatively new antagonist used against migraine, as is pizotyline. Cyproheptadiene is an older serotonin antagonist and antihistaminic. Mirtazapine (Remeron) causes serotonin release, but blocks the 5-HT2 and 5-HT3 subreceptors, effectively augmenting serotonin action at 5-HT1 receptors. Mianserin and homochlorcyclizine also antagonize serotonin receptors.</TD></TR></T></TABLE></CENTER>
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serotonin agonists


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<TD vAlign=center> Sumatriptan activates 5-HT1d terminals, and is used against migraine under the trade name Imitrex. Zolmitriptan (Zomig) and rizatriptan (Maxal) are similar, recently approved, antimigraine serotonin drugs.
Buspirone, ipsapirone and gepirone enjoy 5-HT1 agonist properties with only weak D2 blocking effects. Buspirone is used against anxiety as an alternative to GABA-mimetic sedatives. 8-hydroxy-DPAT acts selectively at 5-HT1a receptors, while 2-methylserotonin activates 5-HT3 terminals.</TD></TR></T></TABLE></CENTER>