NMDA receptor blockade increases locomotor behavior in the zebrafish

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NMDA receptor blockade increases locomotor
behavior in the zebrafish
Charles Drew University 5th Annual Drug Abuse
Research Symposium July 28,2009
Kevin S. Jones, PhD
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What is a zebrafish?
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Zebrafish have 3 developmental stages
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(No Transcript)
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The attributes of studying drug abuse in a
non-mammalian model are not immediately apparent.
Please expound.
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Zebrafish as a model organism

• Advantages
• Small size
• High fecundity
• Sequenced genome
• Optical transparency
• External development
• Genetic manipulation
• Amenable to automated analyses

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Zebrafish as a model organism
Disadvantages 1. Evolutionarily distant from
humans. 2. Limited behavioral repertoire.
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Illy is PCP
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PCP use among 12-13 yr olds
(DAWN report 2007)
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Most psychomotor stimulants directly increase
dopamine activity
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PCP (phencyclidine) blocks a glutamate receptor
PCP
pcp
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MK-801 is a functional analogue of PCP
MK-801
kd lt 5 nM
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Larval zebrafish (10dpf)
96 well plate
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Methods
Data Acquisition

• Zebrafish larvae placed into single wells of a
  multi well plate
• Multi-plate illuminated from below with a 15w
  lightbox
• Larvae given 10 minutes to acclimate
• Subsequent activity recorded for 4 minutes
  on digital camera

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Methods

• Video recordings analyzed off-line
• with particle tracking software

Data Analysis
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Zebrafish have NMDA receptors
Developmental Dynamics 2005 234 756-766

• zNMDAR is 90 IDENTICAL to human NMDAR
• Expressed as early as 24 hpf

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Objective 1

• Characterize the behavioral effects of NMDA
  receptor blockade in zebrafish.

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Prototypical Data
Drug treatment (0h)
Drug treatment (4h)
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Dose Response of MK-801-induced locomotion
EC50 10.3 uM
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Kinetics of behavioral response
Speed (mm/sec)
t (h)
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Developmental Sensitivity
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Most psychomotor stimulants directly increase
dopamine activity
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Dopamine antagonists do not disrupt
MK-801-indcued locomotion
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Acute administration of clozapine does not alter
locomotor effects of MK-801

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Co-admin of ziprasidone attenuates locomotor
effects of MK-801
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Ziprasidone targets several receptors
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Hmmm.. The preliminary data are compelling, but
not convincing.
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Hmmm.. The preliminary data are compelling, but
not convincing. What else you got?
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PCP may increase phosphorylation of GSK-3B at
Tyr279
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Most psychomotor stimulants directly increase
dopamine activity. PCP does not
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How might PCP elicit behavioral effects?
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How might PCP increase locomotion?
5HT neurons
DOPA neurons
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How might PCP increase locomotion?
5HT neurons
DOPA neurons
cognition
sexuality
reward
appetite
motivation
locomotion
Adopted from JT Coyle
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How might PCP increase locomotion?
NMDA receptors
5HT neurons
DOPA neurons
cognition
sexuality
reward
appetite
motivation
locomotion
Adopted from JT Coyle
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How might PCP increase locomotion?
NMDA receptors



X PCP/MK-801
5HT neurons
DOPA neurons
cognition
sexuality
reward
appetite
motivation
locomotion
Adopted from JT Coyle
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How might PCP increase locomotion?
NMDA receptors
X
X
X
X PCP/MK-801
5HT neurons
DOPA neurons
cognition
sexuality
reward
appetite
motivation
locomotion
Adopted from JT Coyle
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How might PCP increase locomotion?
NMDA receptors
X
X
X
GABA interneurons
X PCP/MK-801
5HT neurons
DOPA neurons
cognition
sexuality
reward
appetite
motivation
locomotion
Adopted from JT Coyle
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How might PCP increase locomotion?
NMDA receptors
X
X
X
GABA interneurons
X PCP/MK-801
5HT neurons
DOPA neurons
cognition
sexuality
reward
appetite
motivation
? locomotion
Adopted from JT Coyle
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Summary

• Zebrafish retain the most robust feature of NMDA
  blockade increased locomotion.

• Antipsychotic meds block behavioral effects in
  zebrafish.

• Zebrafish may prove useful for elucidating
  important molecular pathways of drug abuse

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I guess you can use fish to study drugs of abuse!
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Future Directions

• Elucidate relevant circuitry.
• Identify molecular determinants of
  developmental sensitivity.
• Probe for behavioral sensitization.
• Explore neurotoxicology effects.

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Acknowledgments

• Mr. John Chen (UCLA Dental)
• Ms. Roshni Patel (Pomona College)
• Biology Dept Pomona College
• Charles R. Drew University
• National Institute on Drug Abuse