Opposite effects of low and high doses of morphine on neural substrates of aversion in the inferior colliculus.
Behav Pharmacol
; 3(5): 489-495, 1992 Oct.
Article
em En
| MEDLINE
| ID: mdl-11224151
The inferior colliculus (IC) is a well known relay station for auditory pathways in the brainstem. Much evidence has implicated this structure as part of a brain system mediating aversive states, and changes in its functioning as responsible for the occurrence of audiogenic seizures. Rats were implanted with chemitrodes, devices which allow electrical stimulation and microinjections of drugs in the same brain sites. Stepwise increases in the intensity of electrical stimulation of the IC of rats placed inside a circular arena allowed the determination of thresholds for freezing and escape behavior. Morphine (10-40nmol) caused dose-dependent increases in both aversive thresholds. A systemic injection of naloxone reversed the effects of morphine on the centrally induced aversive responses. These data suggest that neural substrates controlling defensive behavior in this structure are under opioid inhibitory control. Higher doses of morphine (80nmol) induced a non-naloxone reversible fearful hyper activity. It is suggested that opioid mechanisms exert an inhibitory control on the neural substrates of aversion in the IC and that high doses of morphine microinjected into IC cause pro-aversive actions probably through non-opioid mechanisms.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Behav Pharmacol
Assunto da revista:
CIENCIAS DO COMPORTAMENTO
/
FARMACOLOGIA
Ano de publicação:
1992
Tipo de documento:
Article
País de afiliação:
Brasil
País de publicação:
Reino Unido