Effects of melatonin on orofacial movements in rats.
BACKGROUND
While reserpine-induced oral movements (OM), an animal model of tardive dyskinesia, are more persistent in old than in adult rats, old animals present spontaneous OM, which are phenomenologically similar to those presented by reserpine-treated adult rats. We postulate that these OM may be the result of oxidative stress induced by both age and reserpine treatment.


OBJECTIVE
We intended to determine the preventative effects of exogenous melatonin (one of the most important endogenous antioxidants) as well as suppression of endogenous melatonin via continuous exposure to light on reserpine- or age-induced OM in rats.


METHODS
Adult (4 months of age) male Wistar rats were repeatedly treated with saline or melatonin (5 mg/kg, IP) and saline or reserpine and kept under a 12-h light/dark cycle for quantification of reserpine-induced OM as well as oxidative stress (via quantification of lipid peroxidation). To verify the effects of endogenous melatonin suppression on reserpine-induced OM, adult rats were repeatedly treated with saline or reserpine and continuously exposed to light. To verify the effects of exogenous melatonin on age-induced OM older (20 months of age) rats were long-term treated with saline or melatonin and kept under a 12-h light/dark cycle.


RESULTS
Melatonin attenuated both reserpine- and age-induced OM. Reserpine enhanced striatal lipid peroxidation, that was prevented by melatonin co-administration. Continuous exposure to light increased spontaneous as well as reserpine-induced OM, indicating that endogenous melatonin may be involved in this movement disorder.


CONCLUSIONS
We suggested that melatonin attenuates both reserpine- and age-induced OM in rats.
Abílio
V C
VC
Department of Pharmacology, Escola Paulista de Medicina/UNIFESP, Edifício José Leal Prado, Rua Botucatu, 862, CEP 04023-062 São Paulo, Brazil.
Vera
J A R
JA
Ferreira
L S M
LS
Duarte
C R M
CR
Carvalho
R C
RC
Grassl
C
C
Martins
C R
CR
Torres-Leite
D
D
Bignotto
M
M
Tufik
S
S
Ribeiro
R de A
Rde A
Frussa-Filho
R
R
D000367:Age Factors; D000818:Animals; D003342:Corpus Striatum / Q000187:drug effects / Q000378:metabolism; D004409:Dyskinesia, Drug-Induced / Q000188:drug therapy* / Q000378:metabolism* / Q000503:physiopathology; D008029:Lighting / Q000009:adverse effects; D015227:Lipid Peroxidation / Q000187:drug effects / Q000502:physiology; D008297:Male; D008550:Melatonin / Q000378:metabolism* / Q000494:pharmacology / Q000627:therapeutic use*; D051381:Rats; D017208:Rats, Wistar; D012110:Reserpine / Q000494:pharmacology
D012110:Reserpine; D008550:Melatonin