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Serotonergic neurons in the median raphe nucleus regulate inhibitory avoidance but not escape behavior in the rat elevated T-maze test of anxiety.
Psychopharmacology (Berl). 2005 Jun; 179(4):733-41.P

Abstract

RATIONALE

A wealth of evidence supports the involvement of the serotonergic neurons of the median raphe nucleus (MRN) in anxiety. However, it is presently unclear whether serotonergic pathways arising from this nucleus play distinguishing regulatory roles in defensive behaviors that have been associated with specific subtypes of anxiety disorders.

OBJECTIVES

To evaluate the role of the MRN serotonergic neurons in the regulation of two defensive behaviors, inhibitory avoidance and escape, which have been related, respectively, to generalized anxiety and panic disorders.

METHODS

Male Wistar rats were submitted to the elevated T-maze test of anxiety after intra-MRN administration of drugs that either non-selectively or selectively change the activity of the serotonergic neurons.

RESULTS

Intra-MRN injection of FG 7142 (0.04 and 0.08 nmol) and kainic acid (0.03 and 0.06 nmol), drugs that non-selectively stimulate the MRN serotonergic neurons, facilitated inhibitory avoidance acquisition, but impaired escape performance. Microinjection of muscimol (0.11 and 0.22 nmol), a compound that non-selectively inhibits the activity of the MRN serotonergic neurons, impaired inhibitory avoidance and facilitated escape performance. Both kainic acid and muscimol also changed rat locomotion in the open-field test. Intra-MRN injection of 8-OH-DPAT (0.6-15 nmol) and WAY-100635 (0.18-0.74 nmol), respectively an agonist and an antagonist of somatodendritic 5-HT(1A) receptors located on serotonergic neurons of the MRN, only affected inhibitory avoidance-while the former inhibited the acquisition of this behavior, the latter facilitated it.

CONCLUSION

MRN serotonergic neurons seem to be selectively involved in the regulation of inhibitory avoidance in the elevated T-maze. This result supports the proposal that 5-HT pathways departing from this nucleus play an important role in anxiety processing, with implications for pathologies such as generalized anxiety disorder.

Authors+Show Affiliations

Dos Santos L
Departament of Psychology and Education, FFCLRP, University of São Paulo, 14040-901, Ribeirão Preto, SP, Brazil.
de Andrade TG
No affiliation info available
Zangrossi H
No affiliation info available

MeSH

8-Hydroxy-2-(di-n-propylamino)tetralinAnimalsAnxietyAvoidance LearningCarbolinesEscape ReactionExcitatory Amino Acid AntagonistsGABA AgonistsKainic AcidMaleMotor ActivityMuscimolNeuronsPiperazinesPyridinesRaphe NucleiRatsRats, WistarReceptor, Serotonin, 5-HT1AReceptors, SerotoninSerotoninSerotonin AntagonistsSerotonin Receptor Agonists

Pub Type(s)

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

Language

eng

PubMed ID

15619105

Citation

Dos Santos, Lucinéia, et al. "Serotonergic Neurons in the Median Raphe Nucleus Regulate Inhibitory Avoidance but Not Escape Behavior in the Rat Elevated T-maze Test of Anxiety." Psychopharmacology, vol. 179, no. 4, 2005, pp. 733-41.
Dos Santos L, de Andrade TG, Zangrossi H. Serotonergic neurons in the median raphe nucleus regulate inhibitory avoidance but not escape behavior in the rat elevated T-maze test of anxiety. Psychopharmacology (Berl). 2005;179(4):733-41.
Dos Santos, L., de Andrade, T. G., & Zangrossi, H. (2005). Serotonergic neurons in the median raphe nucleus regulate inhibitory avoidance but not escape behavior in the rat elevated T-maze test of anxiety. Psychopharmacology, 179(4), 733-41.
Dos Santos L, de Andrade TG, Zangrossi H. Serotonergic Neurons in the Median Raphe Nucleus Regulate Inhibitory Avoidance but Not Escape Behavior in the Rat Elevated T-maze Test of Anxiety. Psychopharmacology (Berl). 2005;179(4):733-41. PubMed PMID: 15619105.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Serotonergic neurons in the median raphe nucleus regulate inhibitory avoidance but not escape behavior in the rat elevated T-maze test of anxiety. AU - Dos Santos,Lucinéia, AU - de Andrade,Telma G C S, AU - Zangrossi,Hélio,Jr Y1 - 2004/12/24/ PY - 2004/03/29/received PY - 2004/10/28/accepted PY - 2004/12/25/pubmed PY - 2005/9/16/medline PY - 2004/12/25/entrez SP - 733 EP - 41 JF - Psychopharmacology JO - Psychopharmacology (Berl) VL - 179 IS - 4 N2 - RATIONALE: A wealth of evidence supports the involvement of the serotonergic neurons of the median raphe nucleus (MRN) in anxiety. However, it is presently unclear whether serotonergic pathways arising from this nucleus play distinguishing regulatory roles in defensive behaviors that have been associated with specific subtypes of anxiety disorders. OBJECTIVES: To evaluate the role of the MRN serotonergic neurons in the regulation of two defensive behaviors, inhibitory avoidance and escape, which have been related, respectively, to generalized anxiety and panic disorders. METHODS: Male Wistar rats were submitted to the elevated T-maze test of anxiety after intra-MRN administration of drugs that either non-selectively or selectively change the activity of the serotonergic neurons. RESULTS: Intra-MRN injection of FG 7142 (0.04 and 0.08 nmol) and kainic acid (0.03 and 0.06 nmol), drugs that non-selectively stimulate the MRN serotonergic neurons, facilitated inhibitory avoidance acquisition, but impaired escape performance. Microinjection of muscimol (0.11 and 0.22 nmol), a compound that non-selectively inhibits the activity of the MRN serotonergic neurons, impaired inhibitory avoidance and facilitated escape performance. Both kainic acid and muscimol also changed rat locomotion in the open-field test. Intra-MRN injection of 8-OH-DPAT (0.6-15 nmol) and WAY-100635 (0.18-0.74 nmol), respectively an agonist and an antagonist of somatodendritic 5-HT(1A) receptors located on serotonergic neurons of the MRN, only affected inhibitory avoidance-while the former inhibited the acquisition of this behavior, the latter facilitated it. CONCLUSION: MRN serotonergic neurons seem to be selectively involved in the regulation of inhibitory avoidance in the elevated T-maze. This result supports the proposal that 5-HT pathways departing from this nucleus play an important role in anxiety processing, with implications for pathologies such as generalized anxiety disorder. SN - 0033-3158 UR - https://www.unboundmedicine.com/medline/citation/15619105/Serotonergic_neurons_in_the_median_raphe_nucleus_regulate_inhibitory_avoidance_but_not_escape_behavior_in_the_rat_elevated_T_maze_test_of_anxiety_ DB - PRIME DP - Unbound Medicine ER -