Abstract
Rationale
Conditioned fear to context causes freezing and cardiovascular changes in rodents and has been used to measure anxiety. It also activates the dorsolateral column of the periaqueductal gray (dlPAG). Microinjections of cannabinoid agonists into the dlPAG produced anxiolytic-like effects in the elevated plus maze, but the effects of these treatments on fear conditioning remains unknown.
Objective
The objective of this study was to verify if intra-dlPAG injection of the CB1 cannabinoid receptor agonist anandamide (AEA) or the anandamide transport inhibitor AM404 would attenuate behavioral (freezing) and cardiovascular (increase of arterial pressure and heart rate) responses of rats submitted to a contextual fear-conditioning paradigm.
Materials and methods
Male Wistar rats with cannulae aimed at the dlPAG were re-exposed to a chamber where they had received footshocks 48 h before. Fifteen minutes before the test, the animals received a first intra-dlPAG injection of vehicle or AM251, a CB1 receptor antagonist (100 pmol/200 nl), followed 5 min later by vehicle, AEA (5 pmol/200 nl) or AM404 (50 pmol/200 nl). Freezing and cardiovascular responses were recorded for 10 min.
Results
Freezing and cardiovascular responses were reduced by administration of either AEA or AM404 into the dlPAG before re-exposition to the aversively conditioned context. These effects were abolished when the animals were locally pretreated with AM251. The latter drug, even at a higher dose (300 pmol), was ineffective when administered alone into the dlPAG.
Conclusion
The results suggest that facilitation of endocannabinoid-mediated neurotransmission in the dlPAG, through activation of local CB1 receptors, attenuates the expression of contextual fear responses.
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References
Adams IB, Compton DR, Martin BR (1998) Assessment of anandamide interaction with the cannabinoid brain receptor: SR 141716A antagonism studies in mice and autoradiographic analysis of receptor binding in rat brain. J Pharmacol Exp Ther 284:1209–1217
Amorapanth P, Nader K, LeDoux JE (1999) Lesions of periaqueductal gray dissociate-conditioned freezing from conditioned suppression behavior in rats. Learn Mem 6:491–499
Bandler R, Carrive P (1988) Integrated defence reaction elicited by excitatory amino acid microinjection in the midbrain periaqueductal grey region of the unrestrained cat. Brain Res 439:95–106
Bandler R, Keay KA, Floyd N, Price J (2000) Central circuits mediating patterned autonomic activity during active vs. passive emotional coping. Brain Res Bull 53:95–104
Berrendero F, Maldonado R (2002) Involvement of the opioid system in the anxiolytic-like effects induced by Delta(9)-tetrahydrocannabinol. Psychopharmacology (Berl) 163:111–117
Blanchard RJ, Blanchard DC (1969) Passive and active reactions to fear-eliciting stimuli. J Comp Physiol Psychol 68:129–135
Bortolato M, Campolongo P, Mangieri RA, Scattoni ML, Frau R, Trezza V, La Rana G, Russo R, Calignano A, Gessa GL, Cuomo V, Piomelli D (2006) Anxiolytic-like properties of the anandamide transport inhibitor AM404. Neuropsychopharmacology 31:2652–2659
Bortolato M, Mangieri RA, Fu J, Kim JH, Arguello O, Duranti A, Tontini A, Mor M, Tarzia G, Piomelli D (2007) Antidepressant-like activity of the fatty acid amide hydrolase inhibitor URB597 in a rat model of chronic mild stress. Biol Psychiatry 62:1103–1110
Carrive P, Leung P, Harris J, Paxinos G (1997) Conditioned fear to context is associated with increased Fos expression in the caudal ventrolateral region of the midbrain periaqueductal gray. Neuroscience 78:165–177
Carrive P, Lee J, Su A (2000) Lidocaine blockade of amygdala output in fear-conditioned rats reduces Fos expression in the ventrolateral periaqueductal gray. Neuroscience 95:1071–1080
Chhatwal JP, Davis M, Maguschak KA, Ressler KJ (2005) Enhancing cannabinoid neurotransmission augments the extinction of conditioned fear. Neuropsychopharmacology 30:516–524
de Oliveira RM, Del Bel EA, Guimarães FS (2001) Effects of excitatory amino acids and nitric oxide on flight behavior elicited from the dorsal periaqueductal gray. Neurosci Biobeh Rev 25:679–685
Devane WA, Dysarz FA 3rd, Johnson MR, Melvin LS, Howlett AC (1988) Determination and characterization of a cannabinoid receptor in rat brain. Mol Pharmacol 34:605–613
Devane WA, Hanus L, Breuer A, Pertwee RG, Stevenson LA, Griffin G, Gibson D, Mandelbaum A, Etinger A, Mechoulam R (1992) Isolation and structure of a brain constituent that binds to the cannabinoid receptor. Science 258:1946–1949
Egertova M, Cravatt BF, Elphick MR (2003) Comparative analysis of fatty acid amide hydrolase and cb(1) cannabinoid receptor expression in the mouse brain: evidence of a widespread role for fatty acid amide hydrolase in regulation of endocannabinoid signaling. Neuroscience 119:481–496
Fanselow MS (1980) Conditioned and unconditional components of post-shock freezing. Pavlov J Biol Sci 15:177–182
Finn DP, Jhaveri MD, Beckett SR, Roe CH, Kendall DA, Marsden CA, Chapman V (2003) Effects of direct periaqueductal grey administration of a cannabinoid receptor agonist on nociceptive and aversive responses in rats. Neuropharmacology 45:594–604
Gill EW, Paton WD, Pertwee RG (1970) Preliminary experiments on the chemistry and pharmacology of cannabis. Nature 228:134–136
Guimarães FS, Carobrez AP, De Aguiar JC, Graeff FG (1991) Anxiolytic effect in the elevated plus-maze of the NMDA receptor antagonist AP7 microinjected into the dorsal periaqueductal grey. Psychopharmacology (Berl) 103:91–94
Herkenham M, Lynn AB, Johnson MR, Melvin LS, de Costa BR, Rice KC (1991) Characterization and localization of cannabinoid receptors in rat brain: a quantitative in vitro autoradiographic study. J Neurosci 11:563–583
Hohmann AG, Suplita RL, Bolton NM, Neely MH, Fegley D, Mangieri R, Krey JF, Walker JM, Holmes PV, Crystal JD, Duranti A, Tontini A, Mor M, Tarzia G, Piomelli D (2005) An endocannabinoid mechanism for stress-induced analgesia. Nature 435:1108–1112
Kathuria S, Gaetani S, Fegley D, Valino F, Duranti A, Tontini A, Mor M, Tarzia G, La Rana G, Calignano A, Giustino A, Tattoli M, Palmery M, Cuomo V, Piomelli D (2003) Modulation of anxiety through blockade of anandamide hydrolysis. Nat Med 9:76–81
Krieger JE, Graeff FG (1985) Defensive behavior and hypertension induced by glutamate in the midbrain central gray of the rat. Braz J Med Biol Res 18:61–67
LeDoux JE, Iwata J, Cicchetti P, Reis DJ (1988) Different projections of the central amygdaloid nucleus mediate autonomic and behavioral correlates of conditioned fear. J Neurosci 8:2517–2529
Matheus MG, Nogueira R, Carobrez AP, Graeff FG, Guimarães FS (1994) Anxiolytic effect of glycine antagonists microinjected into the dorsal periaqueductal grey. Psychopharmacology 13:565–569
Matsuda LA, Lolait SJ, Brownstein MJ, Young AC, Bonner TI (1990) Structure of a cannabinoid receptor and functional expression of the cloned cDNA. Nature 346:561–564
Mechoulam R, Ben-Shabat S, Hanus L, Ligumsky M, Kaminski NE, Schatz AR, Gopher A, Almog S, Martin BR, Compton DR et al (1995) Identification of an endogenous 2-monoglyceride, present in canine gut, that binds to cannabinoid receptors. Biochem Pharmacol 50:83–90
Molchanov ML, Guimarães FS (2002) Anxiolytic-like effects of AP7 injected into the dorsolateral or ventrolateral columns of the periaqueductal gray of rats. Psychopharmacology (Berl) 160:30–38
Moreira FA, Aguiar DC, Guimarães FS (2007) Anxiolytic-like effect of cannabinoids injected into the rat dorsolateral periaqueductal gray. Neuropharmacology 52:958–965
Patel S, Hillard CJ (2006) Pharmacological evaluation of cannabinoid receptor ligands in a mouse model of anxiety: further evidence for an anxiolytic role for endogenous cannabinoid signaling. J Pharmacol Exp Ther 318:304–311
Paxinos G, Watson C (1997) The rat brain in stereotaxic coordinates. 2.ed. Academic, Sydney
Resstel LB, Joca SR, Guimarães FG, Correa FM (2006a) Involvement of medial prefrontal cortex neurons in behavioral and cardiovascular responses to contextual fear conditioning. Neuroscience 143:377–385
Resstel LB, Joca SR, Moreira FA, Correa FM, Guimarães FS (2006b) Effects of cannabidiol and diazepam on behavioral and cardiovascular responses induced by contextual conditioned fear in rats. Behav Brain Res 172:294–298
Rinaldi-Carmona M, Barth F, Heaulme M, Shire D, Calandra B, Congy C, Martinez S, Maruani J, Neliat G, Caput D et al (1994) SR141716A, a potent and selective antagonist of the brain cannabinoid receptor. FEBS Lett 350:240–244
Smith PB, Compton DR, Welch SP, Razdan RK, Mechoulam R, Martin BR (1994) The pharmacological activity of anandamide, a putative endogenous cannabinoid, in mice. J Pharmacol Exp Ther 270:219–227
Sugiura T, Kondo S, Sukagawa A, Nakane S, Shinoda A, Itoh K, Yamashita A, Waku K (1995) 2-Arachidonoylglycerol: a possible endogenous cannabinoid receptor ligand in brain. Biochem Biophys Res Commun 215:89–97
Vaughan CW, Connor M, Bagley EE, Christie MJ (2000) Actions of cannabinoids on membrane properties and synaptic transmission in rat periaqueductal gray neurons in vitro. Mol Pharmacol 57:288–295
Zhang WN, Murphy CA, Feldon J (2004) Behavioural and cardiovascular responses during latent inhibition of conditioned fear: measurement by telemetry and conditioned freezing. Behav Brain Res 154:199–209
Acknowledgments
The authors wish to thank Ivanilda A.C. Fortunato and José Carlos Aguiar for technical support. Research supported by grants from CNPq and FAPESP.
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Resstel and Lisboa contributed equally to this work.
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Resstel, L.B.M., Lisboa, S.F., Aguiar, D.C. et al. Activation of CB1 cannabinoid receptors in the dorsolateral periaqueductal gray reduces the expression of contextual fear conditioning in rats. Psychopharmacology 198, 405–411 (2008). https://doi.org/10.1007/s00213-008-1156-1
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DOI: https://doi.org/10.1007/s00213-008-1156-1