The effects of PD 176252 [3-(1H-indol-3-yl)-N-[1-(5-methoxy-pyridin-2-yl)- cyclohexylmethyl]-2-methyl-2-[3-(nitro-phenyl)ureido] propionamide], a nonpeptide bombesin (BB)BB1/BB2 receptor antagonist, were assessed in rats using several ethologically relevant tests of anxiety. Consistent with a role for the bombesin family of peptides in subserving anxiety behaviors, the antagonist increased social interaction (3.75 and 7.5 mg/kg, i.p.), dose-dependently attenuated the number of vocalizations emitted by guinea pig pups separated from their mother (1-30 mg/kg, i.p.), reduced latency to approach a palatable snack in an anxiogenic (unfamiliar) environment, and reduced the fear-potentiated startle response (5 and 10 mg/kg, i.p., and 100-200 ng per rat, i.c.v.). When administered directly to the dorsal raphé nucleus (DRN), PD 176252 (20-500 ng) increased social interaction under aversive conditions, as did the 5-HT1A receptor agonist 8-hydroxy-2(di-n- propylamino)tetralin (50 ng). Furthermore, intra-DRN microinfusion of the peptide antagonist (PD 176252) suppressed, whereas its agonist [neuromedin B (NMB)-30] promoted, the in vivo release of 5-HT in the ventral hippocampus. In parallel, the suppressed social interaction elicited by intra-DRN administration of NMB was attenuated by a systemically administered 5-HT2C (but not 5-HT1A) receptor antagonist. Together, these findings suggest that endogenous BB-like peptides at the DRN evoke the release of 5-HT from the limbic nerve terminals originating from the raphé, specifically at the ventral hippocampus, resulting in anxiogenesis. The finding that this action was attenuated by BB receptor (BB1 and/or BB2) antagonists suggests that thesecompoundsmayrepresent a novel class of anxiolytic agents. Copyright

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Keywords 5-hydroxytryptamine, Anxiety, Dorsal raphé nucleus, Fear potentiated startle, Guinea pig pup vocalizations, Neuromedin B, Social interaction
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Journal Journal of Neuroscience
Merali, Z. (Zul), Bédard, T. (Tania), Andrews, N. (Nick), Davis, B. (Ben), McKnight, A.T. (Alexander T.), Gonzalez, M.I. (M. Isabel), … Anisman, H. (2006). Bombesin receptors as a novel anti-anxiety therapeutic target: BB 1 receptor actions on anxiety through alterations of serotonin activity. Journal of Neuroscience, 26(41), 10387–10396. doi:10.1523/JNEUROSCI.1219-06.2006