title: Dorsal raphe nucleus regulation of a panic-like defensive behavior evoked by chemical stimulation of the rat dorsal periaqueductal gray matter.
abstract: Electrical or chemical stimulation of the dorsal periaqueductal gray matter (DPAG) evokes escape, a defensive behavior that has been related to panic attacks. Injection of 5-HT(1A) or 5-HT(2A) receptor agonists into this midbrain area inhibits this response. It has been proposed that the impairment of 5-HT mechanisms controlling escape at the level of the DPAG may underlie the susceptibility to panic attacks that characterizes the panic disorder. In this study we evaluated the effects of the pharmacological manipulation of the dorsal raphe nucleus (DRN), which are the main source of 5-HT input to the DPAG, on the escape response evoked in rats by the intra-DPAG injection of the nitric oxide donor SIN-1. The results showed that DRN administration of the 5-HT(1A) receptor agonist 8-OH-DPAT which inhibits the activity of 5-HT neurons favored the expression of escape induced by SIN-1. Intra-DRN injection of the excitatory amino acid kainic acid or the 5-HT(1A) receptor antagonist WAY-100635 did not change escape expression. However, both compounds fully blocked the escape reaction generated by intra-DPAG injection of the excitatory amino acid d,l-homocysteic acid (DLH). Overall, the results indicate that 5-HT neurons in the DRN exert a bidirectional control upon escape behavior generated by the DPAG. Taking into account the effect of WAY-100635 on DLH-induced escape, they also strengthen the view that DRN 5-HT(1A) autoreceptors are under tonic inhibitory influence by 5-HT.
authors.affiliation: Department of Pharmacology, School of Medicine, University of São Paulo, Av. Bandeirantes 3900, Ribeirão Preto, CEP, Brazil.
authors.forename: Tatiana Longo Borges
authors.initials: TL
authors.lastname: Miguel
authors.forename: Roger Luis Henschel
authors.initials: RL
authors.lastname: Pobbe
authors.forename: Ailton
authors.initials: A
authors.lastname: Spiacci Junior
authors.forename: Hélio
authors.initials: H
authors.lastname: Zangrossi Junior
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000494:pharmacology; D000818:Animals; D004195:Disease Models, Animal; D004924:Escape Reaction / Q000187:drug effects / Q000502:physiology*; D006710:Homocysteine / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000494:pharmacology; D007608:Kainic Acid / Q000494:pharmacology; D008297:Male; D008981:Molsidomine / Q000031:analogs & derivatives* / Q000494:pharmacology; D016584:Panic Disorder / Q000503:physiopathology*; D010487:Periaqueductal Gray / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D011903:Raphe Nuclei / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D017208:Rats, Wistar; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists
chemical_list: D010879:Piperazines; D011725:Pyridines; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists; D006710:Homocysteine; C007956:homocysteic acid; C002385:linsidomine; C090413:N-(2-(4-(2-methoxyphenyl)-1-piperazinyl)ethyl)-N-(2-pyridinyl)cyclohexanecarboxamide; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; D008981:Molsidomine; D007608:Kainic Acid