Serotonine and Dopamine in the CNS

Claude de Contrecoeur Cyrano at beehive.twics.com
Fri Jun 7 05:07:48 EST 1996


Dopamine et Sérotonine

Le Rôle de la Dopamine et de la Sérotonine dans le Système Nerveux Central(S.N.C)

The Role of Dopamine and Serotonin in the Central Nervous System(C.N.S)
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Serotonin and dopamine play,normally,opposite roles in the CNS:
Serotonin decreases behaviours while dopamine stimulates behaviours.So serotonin 
enhances INACTIVITY while dopamine stimulates ACTION.
According to Dr.Henri Laborit(the father of chlorpromazine)there is a system of 
Action, in the CNS, linked to a system of inhibition.
There is a balance of actions between dopamine and serotonin.This is called
the Dopamine/serotonin balance.There is also a balance of actions between
serotonin itself.For instance,most serotonin actions decrease dopaminergic
activity while,sometimes,serotonin can,paradoxically,enhance dopamine
influence through 5-HT2A receptors for example.
The balance of inhibition and activation of dopamine by serotonin is called
the Serotonin/Serotonin balance.

Effects of Serotonin on Behaviour
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Serotonin controls the quantity of information flow from memory to 
consciousness.Increasing serotoninergic activity,for instance through the
specific serotonin reuptake blockers,will decrease the quantity of
information flow from memory to consciousness while decreasing serotoniner-
gic activity through hallucinogens(with the notable exception of 5-HT2A
receptors)will increase information flow from memory to consciousnness.Under a 
serotonin reuptake blocker consciousness is nearly devoid of thoughts,at certain 
optimum doses,while under hallucinogens the opposite happens:consciousness is full of 
thoughts.The same holds true with cannabinoids.
Increase in serotonin leads to THYMOANESTHESY which means that serotonin
anesthesises emotions.
Decrease in serotonin(for example through MDMA,MDA,etc)leads to stimulation
of sociability and mood,aggressivity and sexuality,etc,probably by augmenting 
dopaminergic activity normally blocked by serotonin(except 5-HT2A receptors).However 
MDMA and MDA lead only to stimulation of sociability, probably at a site or sites 
modulated by the Median Raphé Nucleus.
Here are some effects of serotonin, as demonstrated through zimelidine and
fluvoxamine:
I.Decrease in informational flow from memory to consciousness:the quantity 
of thoughts per unit of time,under zimelidine or fluvoxamine,reaching
consciousness is diminished as to base-line levels.
2.Motivations are decreased.
3.Emotions are anesthesised
4.Sexual desire is decreased or suppressed
5.Sleep or quasi-sleep is increased
6.Aggression is reduced.
7.Locomotion is diminished
8.Because of (1)obssesive thoughts or suicidal thoughts,etc,are reduced
9.Under fluvoxamine suicidal ideation can be reversed quite fast but not as 
spectacularly as with Gamma-hydroxybutyrate.

Contrary to typical serotoninergic reuptake blockers which induce somnolence
fluoxetine is atypical because it induces insomnia.It can also induce
headaches which are reversed by fluvoxamine.Insomnia is also reversed
through fluvoxamine.As also fluoxetine(Prozac)is SUBHALLUCINOGENIC one
concludes that fluoxetine has a differential tendency to indirectly
stimulate 5-HT2A receptors,thus activating dopaminergic activity.
Activation of dopamine neurotransmission leads to insomnia.


Effects of Dopamine on Behaviour
-----------------------------------------------
The effects of dopamine on behaviour can be evaluated with the dopamine
reuptake blockers amineptine and nomifensine(nomifensine has also a
noradrenergic component).
Stimulation of dopamine neurotransmission can induce the following effects:
I.Mental and motor activation.
2.Stimulation of mood WITHOUT concomittant "euphoria".
3.Amineptine can induce a potentiation of benzodiazepines induced
anxiolysis.
4.Some authors say that amineptine can alleviate some schizophrenic sympt-
oms,which is consistent with the hypothesis of hypofrontality linked
to decrease in dopamine neurotransmission.
5.Dopamine seems to be an UBIQUITOUS METABOLIC ACTIVATOR.It thus activates
neuronal systems while serotonin,normally,seems to deactivate neuronal
systems.So the purpose of dopamine,PER SE,in the CNS seems only to modulate metabolic 
activity of other systems.
In this sense,dopamine IS NOT directly linked to pleasurable experiences.It only 
serves to activate post-dopaminergic systems involved in these behaviours...
6.Dopamine stimulates motivations and lifts undecisiveness.Undecisiveness gives rise 
to self-confidence.If dopamine is overactivated then self-confidence increases to the 
point of being delusional!
7.Activation of some dopamine autoreceptors seems to decrease activity.
So there should also exist a Dopamine/Dopamine balance.

La Sérotonine et la Dopamine dans les Etats de Conscience

Serotonin and Dopamine in States of Consciousness
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A.Depression
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Serotonin alleviates depression by reducing excessive reaction to exogenous or 
endogenous stimuli.Serotonin is an ANTI-STRESS molecule which is very effective 
leading,ultimately,to blunting of emotions such as THYMOANESTHESIA.
Thus serotonin seems to be one of the molecule of PLACIDITY,tranquillity,peace of 
mind.Maybe adepts of Zen could stimulate their serotoninergic system in order to 
attain serenity.

Dopamine alleviates depression by STIMULATING ACTION and lifting undecision.Dopamine 
activates blood-flow which may be an important factor in its anti-depressive action.
Depression is ALSO lifted in the oneiric state,while metabolic activity in the CNS is 
very high.
Depressed people are NOT depressed anymore in the dream state but become,all of a 
sudden,depressed again when they go out of the dream state.This can be explained in 
term of metabolism and in the way memory is structured.
But,apart from myself,nobody else has studied this very interesting problem...

B.Schizophrenia
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Serotonin seems to play a role in the blunting of emotions seen in schizoprenics.
This is why I usually refer to these symptoms as the "serotonomimetic syndrome".
Dopamine HYPOACTIVITY in the frontal cortex is responsible for the negative symptoms 
of schizophrenia while HYPERACTIVITY elsewhere is responsible of the positive 
symptoms.


Conclusion:
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Dopamine and Serotonin seem to work in concert in the nervous system in order to 
MODULATE levels of activities of neuronal systems.
In a way they are analoguous to the peripheral sympathic and parasympathic systems!



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