Cm. Yokoro et al., Acute phenobarbital administration induces hyperalgesia: pharmacological evidence for the involvement of supraspinal GABA-A receptors, BRAZ J MED, 34(3), 2001, pp. 397-405
Citations number
25
Categorie Soggetti
Medical Research General Topics
Journal title
BRAZILIAN JOURNAL OF MEDICAL AND BIOLOGICAL RESEARCH
The aim of the present study was to determine if phenobarbital affects the
nociception threshold. Systemic (1-20 mg/kg) phenobarbital administration d
ose dependently induced hyperalgesia in the tail-flick, hot-plate and forma
lin tests in rats and in the abdominal constriction test in mice. Formalin
and abdominal constriction tests were the most sensitive procedures for the
detection of hyperalgesia in response to phenobarbital compared with the t
ail-flick and hot-plate tests. The hyperalgesia induced by systemic phenoba
rbital was blocked by previous administration of 1 mg/kg ip picrotoxin or e
ither 1-2 mg/kg sc or 10 ng icv bicuculline. Intracerebroventricular phenob
arbital administration (5 mug) induced hyperalgesia in the tail-flick test.
In contrast, intrathecal phenobarbital administration (5 mug) induced anti
nociception and blocked systemic-induced hyperalgesia in this test. We sugg
est that phenobarbital may mediate hyperalgesia through GABA-A receptors at
supraspinal levels and antinociception through the same kind of receptors
at spinal levels.