A neurobehavioral systems analysis of adult rats exposed to methylazoxymethanol acetate on E17: implications for the neuropathology of schizophrenia.
BACKGROUND
As a test of plausibility for the hypothesis that schizophrenia can result from abnormal brain, especially cerebral cortical, development, these studies examined whether, in the rat, disruption of brain development initiated on embryonic day (E) 17, using the methylating agent methylazoxymethanol acetate (MAM), leads to a schizophrenia-relevant pattern of neural and behavioral pathology. Specifically, we tested whether this manipulation leads to disruptions of frontal and limbic corticostriatal circuit function, while producing schizophrenia-like, region-dependent reductions in gray matter in cortex and thalamus.


METHODS
In offspring of rats administered MAM (22 mg/kg) on E17 or earlier (E15), regional size, neuron number and neuron density were determined in multiple brain regions. Spontaneous synaptic activity at prefrontal cortical (PFC) and ventral striatal (vSTR) neurons was recorded in vivio. Finally, cognitive and sensorimotor processes mediated by frontal and limbic corticostriatal circuits were assessed.


RESULTS
Adult MAM-E17-exposed offspring showed selective histopathology: size reductions in mediodorsal thalamus, hippocampus, and parahippocampal, prefrontal, and occipital cortices, but not in sensory midbrain, cerebellum, or sensorimotor cortex. The prefrontal, perirhinal, and occipital cortices showed increased neuron density with no neuron loss. The histopathology was accompanied by a disruption of synaptically-driven "bistable membrane states" in PFC and vSTR neurons, and, at the behavioral level, cognitive inflexibility, orofacial dyskinesias, sensorimotor gating deficits and a post-pubertal-emerging hyper-responsiveness to amphetamine. Earlier embryonic MAM exposure led to microcephaly and a motor phenotype.


CONCLUSIONS
The "MAM-E17" rodent models key aspects of neuropathology in circuits that are highly relevant to schizophrenia.
Department of Neuroscience, University of Pittsburgh, Pittsburgh, Pennsylvania, USA. hm2035@columbia.edu
Holly
H
Moore
J David
JD
Jentsch
Mehdi
M
Ghajarnia
Mark A
MA
Geyer
Anthony A
AA
Grace
D000661:Amphetamine / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D001921:Brain / Q000187:drug effects* / Q000196:embryology / Q000503:physiopathology*; D000697:Central Nervous System Stimulants / Q000494:pharmacology; D003072:Cognition Disorders / Q000139:chemically induced; D004195:Disease Models, Animal; D004409:Dyskinesia, Drug-Induced / Q000209:etiology; D005260:Female; D020233:Gait Disorders, Neurologic / Q000139:chemically induced; D008746:Methylazoxymethanol Acetate / Q000633:toxicity*; D009474:Neurons / Q000187:drug effects; D009498:Neurotoxins / Q000633:toxicity*; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D051381:Rats; D011916:Rats, Inbred F344; D012559:Schizophrenia / Q000139:chemically induced / Q000503:physiopathology*
D000697:Central Nervous System Stimulants; D009498:Neurotoxins; D008746:Methylazoxymethanol Acetate; D000661:Amphetamine