Dopamine D1-like receptor signalling in the hippocampus and amygdala modulates the acquisition of contextual fear conditioning.
BACKGROUND
Dopamine D1-like receptor signalling is involved in contextual fear conditioning, but the brain regions involved and its role in other contextual fear memory processes remain unclear.


OBJECTIVE
The objective of this study was to investigate (1) the effects of SCH 23390, a dopamine D1/D5 receptor antagonist, on contextual fear memory encoding, retrieval and reconsolidation, and (2) if the effects of SCH 23390 on conditioning involve the dorsal hippocampus (DH) and/or basolateral amygdala (BLA).


METHODS
Rats were used to examine the effects of systemically administering SCH 23390 on the acquisition, consolidation, retrieval and reconsolidation of contextual fear memory, and on locomotor activity and shock sensitivity. We also determined the effects of MK-801, an NMDA receptor antagonist, on contextual fear memory reconsolidation. The effects of infusing SCH 23390 locally into DH or BLA on contextual fear conditioning and locomotor activity were also examined.


RESULTS
Systemic administration of SCH 23390 impaired contextual fear conditioning but had no effects on fear memory consolidation, retrieval or reconsolidation. MK-801 was found to impair reconsolidation, suggesting that the behavioural parameters used allowed for the pharmacological disruption of memory reconsolidation. The effects of SCH 23390 on conditioning were unlikely the result of any lasting drug effects on locomotor activity at memory test or any acute drug effects on shock sensitivity during conditioning. SCH 23390 infused into either DH or BLA impaired contextual fear conditioning and decreased locomotor activity.


CONCLUSIONS
These findings suggest that dopamine D1-like receptor signalling in DH and BLA contributes to the acquisition of contextual fear memory.
School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, LE12 5RD, UK.
Florence C
FC
Heath
Regimantas
R
Jurkus
Tobias
T
Bast
Marie A
MA
Pezze
Jonathan L C
JL
Lee
J Peter
JP
Voigt
Carl W
CW
Stevenson
D000679:Amygdala / Q000187:drug effects*; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D003216:Conditioning, Operant / Q000187:drug effects*; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D004597:Electroshock; D005239:Fear / Q000187:drug effects*; D006624:Hippocampus / Q000187:drug effects*; D008297:Male; D008568:Memory / Q000187:drug effects; D009043:Motor Activity / Q000187:drug effects; D051381:Rats; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors*; D015398:Signal Transduction / Q000187:drug effects*
D001552:Benzazepines; D018492:Dopamine Antagonists; D017447:Receptors, Dopamine D1; C534628:SCH 23390; D016291:Dizocilpine Maleate