The amphetamine sensitization model of schizophrenia symptoms and its effect on schedule-induced polydipsia in the rat.
BACKGROUND
Amphetamine enhances dopamine (DA) transmission and induces psychotic states or exacerbates psychosis in at-risk individuals. Amphetamine sensitization of the DA system has been proposed as a rodent model of schizophrenia-like symptoms. In humans, excessive nonphysiologic drinking or primary polydipsia is significantly associated with a diagnosis of schizophrenia. In rodents, nonphysiologic drinking can be induced by intermittent presentation of food in the presence of a drinking spout to a hungry animal; this phenomenon is termed, "schedule-induced polydipsia" (SIP).


OBJECTIVE
This study aims to determine the effects of amphetamine sensitization on SIP.


METHODS
We injected rats with amphetamine (1.5 mg/kg) daily for 5 days. Following 4 weeks of withdrawal, animals were food restricted and exposed to the SIP protocol (noncontingent fixed-time 1-min food schedule) for daily 2-h sessions for 24 days.


RESULTS
Results showed that previously amphetamine-injected animals drank more in the SIP protocol and drank more than controls when the intermittent food presentation schedule was removed.


CONCLUSIONS
These findings suggest that hyperdopaminergia associated with schizophrenia may contribute to the development of polydipsia in this population. Whether animals that develop SIP have DA dysfunction or aberrant activity of other circuits that modulate DA activity has yet to be clearly defined.
Department of Biomedical and Molecular Sciences, Queen's University, 116 Barrie Street, Kingston, ON, Canada, K7L 3N6, erhawken@gmail.com.
Emily R
ER
Hawken
Richard J
RJ
Beninger
D000661:Amphetamine / Q000008:administration & dosage*; D000818:Animals; D000697:Central Nervous System Stimulants / Q000008:administration & dosage*; D004195:Disease Models, Animal; D004326:Drinking / Q000187:drug effects; D004327:Drinking Behavior / Q000187:drug effects; D005508:Food Deprivation; D008297:Male; D059607:Polydipsia, Psychogenic / Q000139:chemically induced*; D017207:Rats, Sprague-Dawley; D012559:Schizophrenia / Q000503:physiopathology*; D013997:Time Factors; D014867:Water / Q000008:administration & dosage
D000697:Central Nervous System Stimulants; D014867:Water; D000661:Amphetamine