Effects of gastrin-releasing peptide agonist and antagonist administered to the basolateral nucleus of the amygdala on conditioned fear in the rat.
BACKGROUND
Bombesin (BB)-like peptides have been shown to affect neuroendocrine and neural functions related to the stress response and the modulation of conditioned fear. In line with this view, central administration of gastrin-releasing peptide (GRP; a mammalian analogue of BB) or its receptor antagonist (D-Tpi6, Leu13 psi[CH2NH]-Leu14) BB(6-14) (RC-3095) modulates conditioned fear.


OBJECTIVE
The present study examined the effects of bilateral infusions of GRP or its receptor antagonist (RC-3095) into the basolateral nucleus of the amygdala (BLA) on the conditioned emotional response.


METHODS
The effects of GRP (150, 300, and 600 ng/0.5 microl) and/or RC-3095 (50, 500, and 1,000 ng/0.5 microl) on contextual and cued fear conditioning were assessed following direct bilateral infusion of these compounds into the BLA.


RESULTS
Both GRP and RC-3095 (all doses) reduced freezing during the contextual testing period but did not influence responding in the cued test. Although both compounds reduced freezing in the contextual paradigms, at a moderate dose pretreatment with RC-3095 attenuated the GRP-elicited decrease in contextual freezing.


CONCLUSIONS
It appears that manipulation of GRP at the BLA may influence the expression of learned fear and that these effects preferentially influence contextual versus cue-dependent emotional responses.
Mountney
Christine
C
School of Psychology, University of Ottawa, Ottawa, Ontario, Canada.
Anisman
Hymie
H
Merali
Zul
Z
D000679:Amygdala / Q000187:drug effects / Q000378:metabolism; D000818:Animals; D001839:Bombesin / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D003213:Conditioning, Psychological / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005239:Fear / Q000187:drug effects*; D019886:Gastrin-Releasing Peptide / Q000008:administration & dosage / Q000494:pharmacology*; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley
D010446:Peptide Fragments; C071363:bombesin (6-14), Tpi(6)-Leu(13)-psi(CH2NH)-Leu(14)-; D019886:Gastrin-Releasing Peptide; D001839:Bombesin