, Volume 206, Issue 2, pp 291–301 | Cite as

Fear-reducing effects of intra-amygdala neuropeptide Y infusion in animal models of conditioned fear: an NPY Y1 receptor independent effect

  • Markus FendtEmail author
  • Hugo Bürki
  • Stefan Imobersteg
  • Kurt Lingenhöhl
  • Kevin H. McAllister
  • David Orain
  • Doncho P. Uzunov
  • Frederique Chaperon
Original Investigation



Neuropeptide Y (NPY) and its receptors are densely localized in brain regions involved in the mediation and modulation of fear, including the amygdala. Several studies showed that central NPY is involved in the modulation of fear and anxiety.


In the present study, we investigated (1) whether intra-amygdala injections of NPY affect the expression of conditioned fear and (2) whether NPY Y1 receptors (Y1R) mediates the effects of these intra-amygdaloid NPY injections.


Intra-amygdala NPY injections robustly decreased the expression of conditioned fear measured by conditioned freezing and fear-potentiated startle. These NPY effects were not mimicked by intra-amygdala injections of the Y1R agonists Y-28 or Y-36, and co-infusion of the Y1R antagonist BIBO 3304 did not block the NPY effects. Furthermore, we tested Y1R-deficient mice in conditioned freezing and found no differences between wild type and mutant littermates. Finally, we injected NPY into the amygdala of Y1R-deficient mice. Y1R deficiency had no effect on the fear-reducing effects of intra-amygdala NPY.


These data show an important role of the transmitter NPY within the amygdala for the expression of conditioned fear. Y1R do not appear to be involved in the mediation of the observed intra-amygdala NPY effects suggesting that these effects are mediated via other NPY receptors.


Anxiety Fear-potentiated startle Freezing Mice Neuropeptides 



Analysis of variance


Conditioned stimulus


Fear-potentiated startle


Neuropeptide Y


NPY Y1 receptor


Sound pressure level



The authors thank Agnes Jeker, Charlotte Huber, and Chantal Portet for their excellent technical help and Dr. Christopher Pryce for his helpful comments on the manuscript.


  1. Antoniadis EA, McDonald RJ (2001) Amygdala, hippocampus, and unconditioned fear. Exp Brain Res 138:200–209PubMedCrossRefGoogle Scholar
  2. Bacchi F, Mathe AA, Jimenez P, Stasi L, Arban R, Gerrard P, Caberlotto L (2006) Anxiolytic-like effect of the selective Neuropeptide Y Y2 receptor antagonist BIIE0246 in the elevated plus-maze. Peptides 27:3202–3207PubMedCrossRefGoogle Scholar
  3. Broqua P, Wettstein JG, Rocher MN, Gauthier-Martin B, Junien JL (1995) Behavioral effects of neuropeptide Y receptor agonists in the elevated plus-maze and fear-potentiated startle procedure. Behav Pharmacol 6:215–222PubMedCrossRefGoogle Scholar
  4. Davis M (1992) The role of the amygdala in fear-potentiated startle: implications for animal models of anxiety. Trends Pharmacol Sci 13:35–41PubMedCrossRefGoogle Scholar
  5. Davis M (1994) The role of the amygdala in emotional learning. Int Rev Neurobiol 36:225–266PubMedCrossRefGoogle Scholar
  6. Davis M (1998) Are different parts of the extended amygdala involved in fear versus anxiety? Biol Psychiatry 44:1239–1247PubMedCrossRefGoogle Scholar
  7. Davis M, Shi C (1999) The extended amygdala: are the central nucleus of the amygdala and the bed nucleus of the stria terminalis differentially involved in fear versus anxiety. Ann NY Acad Sci 877:281–291PubMedCrossRefGoogle Scholar
  8. Etkin A, Wager TD (2007) Functional neuroimaging of anxiety: a meta-analysis of emotional processing in PTSD, social anxiety disorder, and specific phobia. Am J Psychiatry 164:1476–1488PubMedCrossRefGoogle Scholar
  9. Fendt M (2006) Animal models of fear and anxiety. In: Koch M (ed) Animal models of neuropsychiatric diseases. Imperial College Press, London, pp 293–336Google Scholar
  10. Fendt M, Fanselow MS (1999) The neuroanatomical and neurochemical basis of conditioned fear. Neurosci Biobehav Rev 23:743–760PubMedCrossRefGoogle Scholar
  11. Fendt M, Schmid S, Thakker DR, Jacobson LH, Yamamoto R, Mitsukawa K, Maier R, Natt F, Hüsken D, Kelly PH, McAllister KH, Hoyer D, van der Putten H, Cryan JF, Flor PJ (2008) mGluR7 facilitates extinction of aversive memories and controls amygdala plasticity. Mol Psychiatry 13:970–979PubMedCrossRefGoogle Scholar
  12. Garakani A, Mathew SJ, Charney DS (2006) Neurobiology of anxiety disorders and implications for treatment. Mt Sinai J Med 73:941–949PubMedGoogle Scholar
  13. Gehlert DR, Schober DA, Morin M, Berglund MM (2007) Co-expression of neuropeptide YY1 and Y5 receptors results in heterodimerization and altered functional properties. Biochem Pharmacol 74:1652–1664PubMedCrossRefGoogle Scholar
  14. Grillon C, Baas JM (2003) A review of the modulation of the startle reflex by affective states and its application in psychiatry. Clin Neurophysiol 114:1557–1579PubMedCrossRefGoogle Scholar
  15. Grillon C, Baas JM, Pine DS, Lissek S, Lawley M, Ellis V, Levine J (2006) The benzodiazepine alprazolam dissociates contextual fear from cued fear in humans as assessed by fear-potentiated startle. Biol Psychiatry 60:760–766PubMedCrossRefGoogle Scholar
  16. Gutman AR, Yang Y, Ressler KJ, Davis M (2008) The role of neuropeptide Y in the expression and extinction of fear-potentiated startle. J Neurosci 28:12682–12690PubMedCrossRefGoogle Scholar
  17. Heilig M (1995) Antisense inhibition of neuropeptide Y (NPY)-Y1 receptor expression blocks the anxiolytic-like action of NPY in amygdala and paradoxically increases feeding. Regul Pept 59:201–205PubMedCrossRefGoogle Scholar
  18. Heilig M, Söderpalm B, Engel JA, Widerlöv E (1989) Centrally administered neuropeptide Y (NPY) produces anxiolytic-like effects in animal anxiety models. Psychopharmacology 98:524–529PubMedCrossRefGoogle Scholar
  19. Heilig M, McLeod S, Brot M, Heinrichs SC, Menzaghi F, Koob GF, Britton KT (1993) Anxiolytic-like action of neuropeptide Y: mediation by Y1 receptors in amygdala, and dissociation from food intake effects. Neuropsychopharmacology 8:357–363PubMedGoogle Scholar
  20. Heilig M, Zachrisson O, Thorsell A, Ehnvall A, Mottaggui-Tabar S, Sjogren M, Asberg M, Ekman R, Wahlestedt C, Agren H (2004) Decreased cerebrospinal fluid neuropeptide Y (NPY) in patients with treatment refractory unipolar major depression: preliminary evidence for association with preproNPY gene polymorphism. J Psychiatr Res 38:113–121PubMedCrossRefGoogle Scholar
  21. Holmes A, Heilig M, Rupniak NMJ, Steckler T, Griebel G (2003) Neuropeptide systems as novel therapeutic targets for depression and anxiety disorders. Trends Pharmacol Sci 24:580–588PubMedCrossRefGoogle Scholar
  22. Karl T, Burne THJ, Herzog H (2006) Effect of Y1 receptor deficiency on motor activity, exploration, and anxiety. Behav Brain Res 167:87–93PubMedCrossRefGoogle Scholar
  23. Karlsson RM, Holmes A, Heilig M, Crawley JN (2005) Anxiolytic-like actions of centrally-administered neuropeptide Y, but not galanin, in C57BL/6J mice. Pharmacol Biochem Behav 80:427–436PubMedCrossRefGoogle Scholar
  24. Karlsson RM, Choe J, Cameron H, Thorsell A, Crawley J, Holmes A, Heilig M (2008) The neuropeptide Y Y1 receptor subtype is necessary for the anxiolytic-like effects of neuropeptide Y, but not the antidepressant-like effects of fluoxetine, in mice. Psychopharmacology 195:547–557PubMedCrossRefGoogle Scholar
  25. Kask A, Harro J, von Horsten S, Redrobe JP, Dumont Y, Quirion R (2002) The neurocircuitry and receptor subtypes mediating anxiolytic-like effects of neuropeptide Y. Neurosci Biobehav Rev 26:259–283PubMedCrossRefGoogle Scholar
  26. Kim JJ, Jung MW (2006) Neural circuits and mechanisms involved in Pavlovian fear conditioning: a critical review. Neurosci Biobehav Rev 30:188–202PubMedCrossRefGoogle Scholar
  27. Kishi T, Aschkenasi CJ, Choi BJ, Lopez ME, Lee CE, Liu HY, Hollenberg AN, Friedman JM, Elmquist JK (2005) Neuropeptide Y Y1 receptor mRNA in rodent brain: distribution and colocalization with melanocortin-4 receptor. J Comp Neurol 482:217–243PubMedCrossRefGoogle Scholar
  28. Krysiak R, Obuchowicz E, Herman ZS (2000) Conditioned fear-induced changes in neuropeptide Y-like immunoreactivity in rats: the effect of diazepam and buspirone. Neuropeptides 34:148–157PubMedCrossRefGoogle Scholar
  29. LeDoux JE (2000) Emotion circuits in the brain. Annu Rev Neurosci 23:155–184PubMedCrossRefGoogle Scholar
  30. McNaughton N, Corr PJ (2004) A two-dimensional neuropsychology of defense: fear/anxiety and defensive distance. Neurosci Biobehav Rev 28:285–305PubMedCrossRefGoogle Scholar
  31. Mineka S, Oehlberg K (2008) The relevance of recent developments in classical conditioning to understanding the etiology and maintenance of anxiety disorders. Acta Psychol 127:567–580CrossRefGoogle Scholar
  32. Mullins D, Kirby D, Hwa J, Guzzi M, Rivier J, Parker E (2001) Identification of potent and selective neuropeptide Y Y(1) receptor agonists with orexigenic activity in vivo. Mol Pharmacol 60:534–540PubMedGoogle Scholar
  33. Paxinos G, Franklin KBJ (2001) The mouse brain in stereotaxic coordinates, 2nd edn. Academic, San DiegoGoogle Scholar
  34. Pedrazzini T, Seydoux J, Künstner P, Aubert JF, Grouzmann E, Beermann F, Brunner HR (1998) Cardiovascular response, feeding behavior and locomotor activity in mice lacking the NPY Y1 receptor. Nat Med 4:722–726PubMedCrossRefGoogle Scholar
  35. Pich EM, Agnati LF, Zini I, Marrama P, Carani C (1993) Neuropeptide Y produces anxiolytic effects in spontaneously hypertensive rats. Peptides 14:909–912PubMedCrossRefGoogle Scholar
  36. Primeaux SD, Wilson SP, Cusick MC, York DA, Wilson MA (2005) Effects of altered amygdalar neuropeptide Y expression on anxiety-related behaviors. Neuropsychopharmacology 30:1589–1597PubMedCrossRefGoogle Scholar
  37. Rasmusson AM, Hauger RL, Morgan CA III, Bremner JD, Charney DS, Southwick SM (2000) Low baseline and yohimbine-stimulated plasma neuropeptide Y (NPY) levels in combat-related PTSD. Biol Psychiatry 47:526–539PubMedCrossRefGoogle Scholar
  38. Rosen JB (2004) The neurobiology of conditioned and unconditioned fear: a neurobehavioral system analysis of the amygdala. Behav Cogn Neurosci Rev 3:23–41PubMedCrossRefGoogle Scholar
  39. Sajdyk TJ, Vandergriff MG, Gehlert DR (1999) Amygdalar neuropeptide Y Y1 receptors mediate the anxiolytic-like actions of neuropeptide Y in the social interaction test. Eur J Pharmacol 368:143–147PubMedCrossRefGoogle Scholar
  40. Sajdyk TJ, Schober DA, Gehlert DR (2002) Neuropeptide Y receptor subtypes in the basolateral nucleus of the amygdala modulate anxiogenic responses in rats. Neuropharmacology 43:1165–1172PubMedCrossRefGoogle Scholar
  41. Siegl S, Flor PJ, Fendt M (2008) Amygdaloid metabotropic glutamate receptor subtype 7 is involved in the acquisition of conditioned fear. NeuroReport 19:1147–1150PubMedCrossRefGoogle Scholar
  42. Smialowska M, Wieronska JM, Domin H, Zieba B (2007) The effect of intrahippocampal injection of group II and III metobotropic glutamate receptor agonists on anxiety; the role of neuropeptide Y. Neuropsychopharmacology 32:1242–1250PubMedCrossRefGoogle Scholar
  43. Sorensen G, Lindberg C, Wörtwein G, Bolwig TG, Woldbye DPD (2004) Differential roles for neuropeptide Y Y1 and Y5 receptors in anxiety and sedation. J Neurosci Res 77:723–729PubMedCrossRefGoogle Scholar
  44. Tatemoto K, Carlquist M, Mutt V (1982) Neuropeptide Y—a novel brain peptide with structural similarities to peptide YY and pancreatic polypeptide. Nature 296:659–660PubMedCrossRefGoogle Scholar
  45. Wieland HA, Engel W, Eberlein W, Rudolf K, Doods HN (1998) Subtype selectivity of the novel nonpeptide neuropeptide Y Y1 receptor antagonist BIBO 3304 and its effect on feeding in rodents. Br J Pharmacol 125:549–555PubMedCrossRefGoogle Scholar
  46. Wieronska JM, Stachowicz K, Klodzinska A, Smialowska M, Pilc A (2004) Intraamygdaloid administration of BIBO 3304 increases water intake and extends anxiolytic effects. Pol J Pharmacol 56:867–870PubMedGoogle Scholar
  47. Wieronska JM, Smialowska M, Branski P, Gasparini F, Klodzinska A, Szewczyk B, Palucha A, Chojnacka-Wojcik E, Pilc A (2008) In the amygdala anxiolytic action of mGlu5 receptors antagonist MPEP involves neuropeptide Y but not GABAA signaling. Neuropsychopharmacology 29:514–521CrossRefGoogle Scholar
  48. Wilensky AE, Schafe GE, Kristensen MP, LeDoux J (2006) Rethinking the fear circuit: the central nucleus of the amygdala is required for the acquisition, consolidation, and expression of pavlovian fear conditioning. J Neurosci 26:12387–12396PubMedCrossRefGoogle Scholar
  49. Wolak ML, deJoseph MR, Cator AD, Mokashi AS, Brownfield MS, Urban JH (2003) Comparative distribution of neuropeptide YY1 and Y5 receptors in the rat brain by using immunohistochemistry. J Comp Neurol 464:285–311PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2009

Authors and Affiliations

  • Markus Fendt
    • 1
    Email author
  • Hugo Bürki
    • 1
  • Stefan Imobersteg
    • 1
  • Kurt Lingenhöhl
    • 1
  • Kevin H. McAllister
    • 1
  • David Orain
    • 1
  • Doncho P. Uzunov
    • 1
  • Frederique Chaperon
    • 1
  1. 1.Novartis Institutes for BioMedical Research, Neuroscience DA, Neuropsychiatry, Forum 1BaselSwitzerland

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