Serotonin pathway Serotonergic pathways
Some studies indicate a close relationship between 5-HT turnover in brain and platelets. There are similarities between neurons and platelets regarding the mechanisms of 5-HT transport and the presence of certain binding sites including the 5-HT2 receptor [, ]. For example, rats show decreased levels of 5-HT both in platelet-rich plasma and in brain homogenates after the forced swim test (FST), used to assess antidepressant efficacy. This decrease is reduced after acute treatment of animals with a selective serotonin reuptake inhibitor (SSRI) (fluoxetine) and in naive rats, fluoxetine causes an increase in 5-HT . The 5-HT concentration in brain homogenates after chronic (12 days) treatment of rats with an SSRI was comparable to the amount found in platelet-rich plasma. The 5-HT concentration in isolated platelets returned to control levels at day 12, which may reflect comparable changes in neurons.
Serotonin and dopamine biosynthetic pathways
The observation that current antidepressant therapies need a sustained treatment of 2–4 weeks to be effective suggests that adaptive changes in both serotonergic and noradrenergic neurotransmission and downstream neural adaptation (e.g. the BDNF receptor signaling pathway) rather than only the elevation in synaptic monoamine levels itself are responsible for the therapeutic effects , .
It's likely that these behaviors are coping mechanisms for weak or overwhelmingly strong sensations that are alleviated with higher values of serotonin synthesis.
Serotonin, depression, and aggression: The problem of brain energy
In , ascarosides were first identified as signaling molecules regulating the population density-dependent formation of dauer larvae. larvae interrupt normal reproductive development and enter the dauer diapause in response to adverse environmental conditions and high population density (recently reviewed in ). Dauer larvae do not feed and are highly stress resistant and long lived (up to 8 months). Upon improvement of environmental conditions, dauer larvae resume normal development resulting in reproductive adults with a normal lifespan (; ). Extensive mutant screens led to identification of about 40 dauer formation defective (Daf) mutants that are either unable to form dauers (dauer formation defective, Daf-d) or constitutively form dauer larvae (Daf-c) (; ). Epistasis analysis of genes revealed a complex signaling network that regulates dauer formation and exit and is based on conserved signaling pathways including steroid hormone, serotonin, cGMP, TGF-β, and insulin/IGF signaling.
Mouse Dopamine & Serotonin Pathway PCR array
In the autistic children between the ages of 3 and 8, serotonin synthesis values were only 1 * higher than the adult values." This would suggest that especially for autistic children, medication that mimics serotonin would be helpful in targeting specific behaviors that are characteristic of autism.Not all behaviors associated with autism are affected by changes in the values of serotonin synthesis, but those that arise from reduced 5-HTT (the serotonin transporter) such as aggression and repetitive behavior are alleviated.
We construct a mathematical model of serotonin synthesis, ..
Tryptophan is also metabolized on a different pathway, not all of it is converted into 5-HTP. This brain boosting herbal product is a sophisticated cognitive formula.
KEGG PATHWAY: Tryptophan metabolism - Reference pathway
Depression has a multi-symptom pathology and may probably be caused by flaws in several neurotransmitter systems and molecular signalling pathways. Yet, the serotonergic system may play an important role as it is a modulatory system, influencing the activity of many other neurotransmitter pathways throughout the brain.