SEROTONIN AND AUTISM

1
SEROTONIN AND AUTISM
2
OVERVIEW

• Serotonin and Brain Development
• Serotonin in Autism
• Some Studies
• Brain serotonin synthesis capacity
• Hyperserotoninemia and serotonin receptor
  antibodies
• Altered serotonin synthesis
• Serotonin Reuptake Inhibitors

3
SEROTONIN AND BRAIN DEVELOPMENT

• regulator of brain development
• autoregulation
• development of target tissue
• disruption leave permanent alterations
• role in synaptic pruning
• early appearance
• wide distribution of terminals

4
SEROTONIN IN AUTISM

• theoretical considerations underlying rationale
  for the study of serotonin
• role in neurodevelopment
• rich innervation of limbic areas
• serotonins involvement in behaviours
• empirical basis

5

• increase in blood serotonin
• loss of serotonin terminals
• elevated levels of platelet serotonin
• group mean elevations of 25 to 50
• not related to intelligence
• mechanism of alteration and possible relationship
  to brain abnormalities remain unknown

6
SOME STUDIES - 1. Brain serotonin synthesis
capacity

• results
• undergo period during which serotonin synthesis
  capacity is higher than adults
• sex difference
• autistic children did not show expected changes
• conclusion
• Suggests that developmental regulation of
  serotonin synthesis is involved in the
  pathogenesis of autism

7
2. Hyperserotoninemia and serotonin receptor
antibodies

• 30-66 of autistic children
• some also have autoantibodies to brain serotonin
  receptor
• results
• significantly higher levels of serotonin
• hyperserotoninemia found in 50 of autistic
  children
• inhibition of serotonin receptor binding

8

• cause or consequence?
• conclusion
• contribution to autoimmune pathogenesis of autism
  

9
3. Altered serotonin synthesis

• elevated serotonin synthesis in contralateral
  dentate nucleus
• asymmetry differences
• frontal cortex
• thalamus
• dentate nucleus
• mechanism underlying pathophysiology

10
SEROTONIN REUPTAKE INHIBITORS

• effective and relatively well tolerated for both
  adult population and children
• symptomatic improvement in treatment of both
  adults and children
• compulsive symptoms
• repetitive behaviours
• aggression
• perhaps self-injurious behaviours

11

• earlier studies were on fluoxetine
• response strongly correlated with family history
  of major affective disorder and unusual
  intellectual achievement
• more recent ones include fluvoxamine, citalopram
• treatments that decrease serotonergic
  neurotransmission worsens symptoms