Delayed onset of prepulse inhibition deficits following kainic acid treatment on postnatal day 7 in rats.
Abnormal activity in corticolimbic circuits during development may be a predisposing factor for schizophrenia. Permanent or temporary lesions of limbic structures such as the ventral hippocampus and basolateral amygdala in rats on postnatal day (PND) 7 result in functional changes similar to some behavioural and cognitive signs of schizophrenia. The present experiments tested whether transient increases in the neural activity of corticolimbic circuits on PND 7 would result in similar behavioural changes. Long-Evans rats were treated with either kainic acid (KA, 1.5 mg/kg, i.p.) or saline on PND 7 and tested for prepulse inhibition (PPI) of the acoustic startle response and spontaneous locomotor activity both in a novel environment and following amphetamine treatment before puberty (PND 35) and in early adulthood (PND 56). In subgroups of animals PPI was also measured following apomorphine administration (0.2 mg/kg) and spatial learning and memory were tested in the water maze. Rats treated with KA were indistinguishable from saline-treated animals on PND 35. However, on PND 56, KA-treated animals showed a subtle consistent decrease in PPI relative to control animals, but did not show increased sensitivity to the disruptive effects of a low dose of apomorphine on PPI. Locomotor responses to novelty or amphetamine were not reliably altered in the KA-treated animals. KA- and saline-treated animals performed similarly in the water maze. These results support the hypothesis that neural hyperactivity on PND 7 in rats causes behavioural changes in early adulthood that resemble some symptoms of schizophrenia. These pharmacological data suggest that the changes are not mediated by postsynaptic alterations in mesolimbic dopamine transmission.
Howland
John G
JG
Department of Psychology and the Brain Research Centre, University of British Columbia, Vancouver, Canada.
Hannesson
Darren K
DK
Phillips
Anthony G
AG
D000161:Acoustic Stimulation / Q000379:methods; D000367:Age Factors; D000661:Amphetamine / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D001058:Apomorphine / Q000494:pharmacology; D001522:Behavior, Animal; D002540:Cerebral Cortex / Q000187:drug effects* / Q000502:physiology; D004195:Disease Models, Animal; D018491:Dopamine Agonists / Q000494:pharmacology; D018765:Dopamine Uptake Inhibitors / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D018690:Excitatory Amino Acid Agonists / Q000633:toxicity; D005106:Exploratory Behavior / Q000187:drug effects; D005260:Female; D006624:Hippocampus / Q000187:drug effects / Q000473:pathology; D007266:Inhibition, Psychological; D007608:Kainic Acid / Q000633:toxicity*; D008032:Limbic System / Q000187:drug effects* / Q000502:physiology; D008297:Male; D018782:Maze Learning / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D011247:Pregnancy; D051381:Rats; D020318:Rats, Long-Evans; D011930:Reaction Time / Q000187:drug effects; D013216:Reflex, Startle / Q000187:drug effects; D012559:Schizophrenia / Q000139:chemically induced* / Q000503:physiopathology
D018491:Dopamine Agonists; D018765:Dopamine Uptake Inhibitors; D018690:Excitatory Amino Acid Agonists; D000661:Amphetamine; D001058:Apomorphine; D007608:Kainic Acid