• Christine Mountney, Hymie Anisman, and Zul Merali.
• School of Psychology, University of Ottawa, Ottawa, Ontario, Canada.
• Psychopharmacology (Berl.). 2008 Sep 1; 200 (1): 51-8.

RationaleBombesin (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.ObjectiveThe 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.MethodsThe 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.ResultsBoth 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.ConclusionsIt 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.

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