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Regulation of conditioned and unconditioned fear in rats by 5-HT1A receptors in the dorsal periaqueductal gray.
Pharmacol Biochem Behav. 2008 Mar; 89(1):76-84.PB

Abstract

Studies on the involvement of 5-HT1-mediated mechanisms in the dorsal periaqueductal gray (dPAG) of animals with past stressful experiences have not been conducted so far. We investigated the role of 5-HT1 receptors in the dPAG of rats previously submitted to contextual fear conditioning. Defensive behaviors induced by activation of the dPAG were assessed by measuring the lowest electric current applied to this structure (threshold) able to produce freezing and escape responses during testing sessions of contextual fear conditioning, in which animals were placed in a context previously paired to footshocks. The 5-HT1A function of the dPAG was evaluated by local injections of 8-OH-DPAT (4 and 8 nmol/0.2 microL) and WAY-100635 (10 nmol/0.2 microL), selective agonist and antagonist of 5-HT1A receptors, respectively. In accordance with previous studies, 8-OH-DPAT increased aversive thresholds (antiaversive effects) but injections of WAY 100635 into the dPAG did not produce significant effects on the aversive thresholds in naive rats. However, the aversive thresholds of animals exhibiting contextual fear remained unchanged with both treatments. Moreover, 8-OH-DPAT and WAY 100635 did not change the dPAG post-stimulation freezing. The present results suggest that the stressful experience of being fear conditioned has an effect on the role of the 5-HT1A receptors in mediating unconditioned fear. Also, the reduction in the regulation of the defensive behaviors by 5-HT1A-mediated mechanisms in the dPAG of these animals may underlie the stress precipitated psychopathology associated with the neural substrates of aversion of the dPAG.

Authors+Show Affiliations

Broiz AC
Instituto de Neurociências & Comportamento-INeC, Campus USP, 14040-901, Ribeirão Preto, SP, Brazil.
Oliveira LC
No affiliation info available
Brandão ML
No affiliation info available

MeSH

8-Hydroxy-2-(di-n-propylamino)tetralinAnimalsConditioning, PsychologicalCuesElectric StimulationElectroshockFearMaleMicroinjectionsPeriaqueductal GrayPiperazinesPyridinesRatsRats, WistarReceptor, Serotonin, 5-HT1ASerotonin AntagonistsSerotonin Receptor Agonists

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

18076976

Citation

Broiz, Ana Carolina, et al. "Regulation of Conditioned and Unconditioned Fear in Rats By 5-HT1A Receptors in the Dorsal Periaqueductal Gray." Pharmacology, Biochemistry, and Behavior, vol. 89, no. 1, 2008, pp. 76-84.
Broiz AC, Oliveira LC, Brandão ML. Regulation of conditioned and unconditioned fear in rats by 5-HT1A receptors in the dorsal periaqueductal gray. Pharmacol Biochem Behav. 2008;89(1):76-84.
Broiz, A. C., Oliveira, L. C., & Brandão, M. L. (2008). Regulation of conditioned and unconditioned fear in rats by 5-HT1A receptors in the dorsal periaqueductal gray. Pharmacology, Biochemistry, and Behavior, 89(1), 76-84.
Broiz AC, Oliveira LC, Brandão ML. Regulation of Conditioned and Unconditioned Fear in Rats By 5-HT1A Receptors in the Dorsal Periaqueductal Gray. Pharmacol Biochem Behav. 2008;89(1):76-84. PubMed PMID: 18076976.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Regulation of conditioned and unconditioned fear in rats by 5-HT1A receptors in the dorsal periaqueductal gray. AU - Broiz,Ana Carolina, AU - Oliveira,Luciana Chrystine, AU - Brandão,Marcus Lira, Y1 - 2007/11/21/ PY - 2007/08/30/received PY - 2007/10/23/revised PY - 2007/11/14/accepted PY - 2007/12/14/pubmed PY - 2008/4/10/medline PY - 2007/12/14/entrez SP - 76 EP - 84 JF - Pharmacology, biochemistry, and behavior JO - Pharmacol Biochem Behav VL - 89 IS - 1 N2 - Studies on the involvement of 5-HT1-mediated mechanisms in the dorsal periaqueductal gray (dPAG) of animals with past stressful experiences have not been conducted so far. We investigated the role of 5-HT1 receptors in the dPAG of rats previously submitted to contextual fear conditioning. Defensive behaviors induced by activation of the dPAG were assessed by measuring the lowest electric current applied to this structure (threshold) able to produce freezing and escape responses during testing sessions of contextual fear conditioning, in which animals were placed in a context previously paired to footshocks. The 5-HT1A function of the dPAG was evaluated by local injections of 8-OH-DPAT (4 and 8 nmol/0.2 microL) and WAY-100635 (10 nmol/0.2 microL), selective agonist and antagonist of 5-HT1A receptors, respectively. In accordance with previous studies, 8-OH-DPAT increased aversive thresholds (antiaversive effects) but injections of WAY 100635 into the dPAG did not produce significant effects on the aversive thresholds in naive rats. However, the aversive thresholds of animals exhibiting contextual fear remained unchanged with both treatments. Moreover, 8-OH-DPAT and WAY 100635 did not change the dPAG post-stimulation freezing. The present results suggest that the stressful experience of being fear conditioned has an effect on the role of the 5-HT1A receptors in mediating unconditioned fear. Also, the reduction in the regulation of the defensive behaviors by 5-HT1A-mediated mechanisms in the dPAG of these animals may underlie the stress precipitated psychopathology associated with the neural substrates of aversion of the dPAG. SN - 0091-3057 UR - https://www.unboundmedicine.com/medline/citation/18076976/Regulation_of_conditioned_and_unconditioned_fear_in_rats_by_5_HT1A_receptors_in_the_dorsal_periaqueductal_gray_ DB - PRIME DP - Unbound Medicine ER -
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