title: Effect of age on antinociceptive effects of elevated plus-maze exposure.
abstract: It has been suggested that anxiety may be a critical factor in certain forms of non-opioid environmental analgesia. Furthermore, age has been reported to increase the anxiety levels in rats as measured in the elevated plus-maze. In the present investigation 10 young (3 months), 10 middle-aged (14-16 months) and 10 old (28-30 months) male Wistar rats were tested by the tail withdrawal assay of nociception before (baseline), and at 0 (T1) and 10 (T2) min after a 5-min exposure to the elevated plus-maze apparatus. Only old rats presented an increase in tail withdrawal latencies after elevated plus-maze exposure, even though this effect was statistically significant only immediately after exposure to the apparatus (baseline = 2.5 +/- 0.3 s; T1 = 3.8 +/- 0.3 s; T2 = 3.3 +/- 0.4 s). The results indicate that exposure to the elevated plus-maze induces a rapidly reversed and age-dependent antinociception in rats. They are also consistent with the proposed greater sensitivity of old rats to anxiogenic effects of the plus-maze.
authors.affiliation: Departamento de Farmacologia, Escola Paulista de Medicina, São Paulo, Brasil.
authors.forename: R
authors.initials: R
authors.lastname: Frussa-Filho
authors.forename: J R
authors.initials: JR
authors.lastname: Otoboni
authors.forename: A D
authors.initials: AD
authors.lastname: Giannotti
authors.forename: A C
authors.initials: AC
authors.lastname: Amaral
authors.forename: I M
authors.initials: IM
authors.lastname: Conceição
mesh_terms: D000375:Aging / Q000502:physiology*; D000698:Analgesia; D000818:Animals; D001007:Anxiety / Q000503:physiopathology; D008297:Male; D010146:Pain / Q000503:physiopathology*; D017288:Pain Threshold / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D013623:Tail