title: Rat exposure in mice with neuropathic pain induces fear and antinociception that is not reversed by 5-HT2C receptor activation in the dorsal periaqueductal gray.
abstract: Previous studies have demonstrated that serotonin 5-HT2C receptors in the dorsal periaqueductal gray (dPAG) mediate both anxiety and antinociception in mice submitted to the elevated plus maze. The present study examined the effects of intra-dPAG infusion of the serotonin 5-HT2C receptor agonist (MK-212) in the defensive reactions and antinociception in mice with neurophatic pain confronted by a predator. Neuropathic pain was induced by chronic constriction injury (CCI) of the sciatic nerve, and predator confrontation was performed using the rat exposure test (RET). Our results demonstrated that both sham-operated and CCI mice exhibited intense defensive reactions when confronted by rats. However, rat-exposed CCI mice showed reduced pain reactivity in comparison to CCI mice exposed to a toy rat. Intra-dPAG infusion of MK-212 prior to predator exposure did not significantly alter defensive or antinociceptive responses. To our knowledge, our results represent the first evidence of RET-induced antinociception in mice. Moreover, the results of the present study suggest that 5-HT2C receptor activation in the dPAG is not critically involved in the control of predator-evoked fearful or antinociceptive responses.
authors.affiliation: Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP, 13565-905, Brazil; Joint Graduate Program in Physiological Sciences UFSCar/UNESP. Rod. Washington Luís, Km 235, São Carlos, SP, 13565-905, Brazil.
authors.forename: Elke Mayumi
authors.initials: EM
authors.lastname: Furuya-da-Cunha
authors.affiliation: Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP, 13565-905, Brazil; Graduate Program in Psychology UFSCar. Rod. Washington Luís, Km 235, São Carlos, SP, 13565-905, Brazil.
authors.forename: Rimenez Rodrigues de
authors.initials: RR
authors.lastname: Souza
authors.affiliation: Psychobiology Group/Department of Psychology/CECH-UFSCar, São Carlos, SP, 13565-905, Brazil; Joint Graduate Program in Physiological Sciences UFSCar/UNESP. Rod. Washington Luís, Km 235, São Carlos, SP, 13565-905, Brazil; Graduate Program in Psychology UFSCar. Rod. Washington Luís, Km 235, São Carlos, SP, 13565-905, Brazil; Neuroscience and Behavioral Institute, Av. do Café, 2.450, 14050-220 Ribeirão Preto, SP, Brazil. Electronic address: souzaalm@ufscar.br.
authors.forename: Azair
authors.initials: A
authors.lastname: Canto-de-Souza
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001058:Apomorphine / Q000494:pharmacology; D004195:Disease Models, Animal; D018491:Dopamine Agonists / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D005106:Exploratory Behavior / Q000187:drug effects; D005239:Fear / Q000523:psychology*; D008297:Male; D051379:Mice; D008845:Microinjections; D010147:Pain Measurement; D010487:Periaqueductal Gray / Q000187:drug effects / Q000378:metabolism*; D011719:Pyrazines / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D044405:Receptor, Serotonin, 5-HT2C / Q000378:metabolism*; D012585:Sciatica / Q000473:pathology* / Q000523:psychology*; D017366:Serotonin Receptor Agonists / Q000494:pharmacology
chemical_list: D018491:Dopamine Agonists; D011719:Pyrazines; D044405:Receptor, Serotonin, 5-HT2C; D017366:Serotonin Receptor Agonists; C014896:6-chloro-2-(1-piperazinyl)pyrazine; D001058:Apomorphine
keywords: 5-HT(2C); Antinociception; Anxiety; Chronic constriction injury; Periaqueductal gray; Rat exposure test