Impaired in vivo synaptic plasticity in dentate gyrus and spatial memory in juvenile rats induced by prenatal morphine exposure.
Prenatal morphine exposure induces neurobiological changes, including deficits in learning and memory, in juvenile rat offspring. However the effects of this exposure on hippocampal plasticity, which is critical for learning and memory processes, are not well understood. The present study investigates the alterations of spatial memory and in vivo hippocampal synaptic plasticity in juvenile rats prenatally exposed to morphine. On gestation days 11-18, pregnant rats were randomly chosen to be injected twice daily with morphine or saline. Each juvenile offspring (postnatal day 22-31) performed one two-trial Y-maze task to evaluate spatial memory. Afterwards, the in vivo field excitatory postsynaptic potential (fEPSP) and population spike (PS) were recorded in the perforant path dentate gyrus (DG) pathway in the hippocampus. Prenatal morphine exposure reduced depotentiation (DP), but not long-term potentiation (LTP), of the EPSP slope. However, both LTP and DP of the EPSP slope were depressed in prenatal morphine-exposed juvenile offspring. The morphine group also showed poorer performance for the Y-maze task than the control group. Depressed PS LTP, but not EPSP LTP, in the morphine group suggested that prenatal morphine exposure changed GABAergic inhibition, which mediates EPSP-spike potentiation. Then a loss of GABA-containing neurons in the DG area of the morphine group was observed using immunohistochemistry. Taken together, our results suggest that prenatal morphine exposure impairs the juvenile offspring's dentate synaptic plasticity and spatial memory, and that decreased GABAergic inhibition may play a role in these effects. These findings might contribute to an explanation for the cognitive deficits in children whose mothers abuse opiates during pregnancy.
Niu
Lei
L
Hefei National Laboratory for Physical Sciences at Microscale and School of Life Science, University of Science and Technology of China, Hefei, Anhui, People's Republic of China.
Cao
Bing
B
Zhu
Hong
H
Mei
Bin
B
Wang
Ming
M
Yang
Yupeng
Y
Zhou
Yifeng
Y
D000200:Action Potentials; D000818:Animals; D016923:Cell Death / Q000187:drug effects; D018891:Dentate Gyrus / Q000187:drug effects / Q000254:growth & development* / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials; D005260:Female; D017774:Long-Term Potentiation; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D008568:Memory / Q000187:drug effects* / Q000502:physiology; D009020:Morphine / Q000494:pharmacology*; D009294:Narcotics / Q000494:pharmacology*; D009473:Neuronal Plasticity / Q000187:drug effects* / Q000502:physiology; D009474:Neurons / Q000187:drug effects / Q000502:physiology; D019580:Perforant Pathway / Q000187:drug effects / Q000254:growth & development / Q000502:physiology; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013028:Space Perception / Q000187:drug effects* / Q000502:physiology; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D005680:gamma-Aminobutyric Acid / Q000378:metabolism
D009294:Narcotics; D005680:gamma-Aminobutyric Acid; D009020:Morphine