Effect of the GABAergic System on Memory Formation and State-Dependent Learning Induced by Morphine in Rats

In the present study, the effects of intraperitoneal injections of GABA A receptor agonist and antagonist on memory formation and morphine state-dependent learning were investigated in rats. Pre-training administration of morphine (1–15 mg/kg) in a step-down passive avoidance task induced state-depe...

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Veröffentlicht in:Pharmacology 2006-01, Vol.76 (2), p.93-100
Hauptverfasser: Zarrindast, Mohammad-Reza, Noorbakhshnia, Maryam, Motamedi, Freshteh, Haeri-Rohani, Ali, Rezayof, Ameneh
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Sprache:eng
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Zusammenfassung:In the present study, the effects of intraperitoneal injections of GABA A receptor agonist and antagonist on memory formation and morphine state-dependent learning were investigated in rats. Pre-training administration of morphine (1–15 mg/kg) in a step-down passive avoidance task induced state-dependent learning with impaired memory retrieval on the test day. The impairment of memory was restored after the pre-test administration of the same dose of morphine. The pre-test administration of the GABA A receptor agonist, muscimol (0.01, 0.05 and 0.1 mg/kg), significantly decreased state-dependent retrieval induced by pre-test morphine (5 mg/kg). The state-dependency effect of morphine (1 mg/kg) was significantly potentiated by the pre-test administration of the GABA A receptor antagonist, bicuculline (0.125, 0.25 and 0.5 mg/kg). Furthermore, the pre-training injection of muscimol (0.01 mg/kg) impaired memory retrieval which was restored by pre-test morphine (1, 3 and 5 mg/kg) administration. However, the pre-training administration of bicuculline did not affect retention by itself. In addition, amnesia induced by pre-training morphine (5 mg/kg) was significantly reversed in rats which had received pre-test injections of muscimol (0.01, 0.05 and 0.1 mg/kg). Pre-test injections of bicuculline (0.125, 0.25 and 0.5 mg/kg) significantly decreased morphine-induced amnesia. It is concluded that the GABA A receptor mechanisms may be involved in the memory formation and it is postulated that these receptors may play an important role in morphine state-dependent learning.
ISSN:0031-7012
1423-0313
DOI:10.1159/000089934