ABSTRACT
The aim of the present study was to determine if phenobarbital affects the nociception threshold. Systemic (1-20 mg/kg) phenobarbital administration dose dependently induced hyperalgesia in the tail-flick, hot-plate and formalin 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 tail-flick and hot-plate tests. The hyperalgesia induced by systemic phenobarbital was blocked by previous administration of 1 mg/kg ip picrotoxin or either 1-2 mg/kg sc or 10 ng icv bicuculline. Intracerebroventricular phenobarbital administration (5 æg) induced hyperalgesia in the tail-flick test. In contrast, intrathecal phenobarbital administration (5 æg) induced antinociception and blocked systemic-induced hyperalgesia in this test. We suggest that phenobarbital may mediate hyperalgesia through GABA-A receptors at supraspinal levels and antinociception through the same kind of receptors at spinal levels
Subject(s)
Animals , Male , Rats , Mice , Hyperalgesia/physiopathology , Hypnotics and Sedatives/administration & dosage , Phenobarbital/administration & dosage , Receptors, GABA-A/drug effects , Spinal Cord/drug effects , Analysis of Variance , Bicuculline/pharmacology , Dose-Response Relationship, Drug , GABA Antagonists/pharmacology , Hyperalgesia/chemically induced , Motor Activity/drug effects , Pain Measurement , Picrotoxin/pharmacology , Rats, Sprague-DawleyABSTRACT
A produçäo de adenosina 3, 5 - monofosfato cíclico (AMPc) foi avaliada em fatias de fígado de frangos de corte que receberam dieta experimental contendo fosfato bicálcico ou fosfato de rocha de Araxá, com alto teor de flúor, como fonte de fósforo, em dois períodos distintos do 1§ ao 42§ e do 21§ ao 42§ dias de idade. A ingestäo da dieta formulada com fosfato de rocha de Araxá desde o 1§ dia de vida, provocou elevaçäo da produçäo de AMPc no fígado dos frangos de corte. Entretanto a utilizaçäo da mesma dieta a partir do 21§ de idade näo alterou significativamente (P>0,05) a produçäo hepática de AMPc nas aves, sugerindo que a influência da alta ingestäo do flúor presente no fosfato de rocha de Araxá sobre o AMPc hepático dos frangos de corte é dependente da idade em que a administraçäo da dieta é iniciada