Nicotine improves morphine-induced impairment of memory: possible involvement of N-methyl-D-aspartate receptors in the nucleus accumbens.
The possible involvement of N-methyl-D-aspartate (NMDA) receptors in the nucleus accumbens (NAc) in nicotine's effect on impairment of memory by morphine was investigated. A passive avoidance task was used for memory assessment in male Wistar rats. Subcutaneous (s.c.) administration of morphine (5 and 10 mg/kg) after training impaired memory performance in the animals when tested 24 h later. Pretest administration of the same doses of morphine reversed impairment of memory because of post-training administration of the opioid. Moreover, administration of nicotine (0.2 and 0.4 mg/kg, s.c.) before the test prevented impairment of memory by morphine (5 mg/kg) given after training. Impairment of memory performance in the animals because of post-training administration of morphine (5 mg/kg) was also prevented by pretest administration of a noncompetitive NMDA receptor antagonist, MK-801 (0.75 and 1 microg/rat). Interestingly, an ineffective dose of MK-801 (0.5 microg/rat) in combination with low doses (0.075 and 0.1 mg/kg) of nicotine, which had no effects alone, synergistically improved memory performance impaired by morphine given after training. On the other hand, pretest administration of NMDA (0.1 and 0.5 microg/rat), which had no effect alone, in combination with an effective dose (0.4 mg/kg, s.c.) of nicotine prevented the improving effect of nicotine on memory impaired by pretreatment morphine. The results suggest a possible role for NMDA receptors of the NAc in the improving effect of nicotine on the morphine-induced amnesia.
Ahmadi
Shamseddin
S
Department of Animal biology, School of Biology, University College of Science, University of Tehran, Tehran, Iran.
Zarrindast
Mohammad Reza
MR
Haeri-Rohani
Ali
A
Rezayof
Ameneh
A
Nouri
Maryam
M
D000818:Animals; D016291:Dizocilpine Maleate / Q000494:pharmacology; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced* / Q000517:prevention & control; D009020:Morphine / Q000494:pharmacology*; D018696:Neuroprotective Agents / Q000494:pharmacology; D009538:Nicotine / Q000494:pharmacology*; D009714:Nucleus Accumbens / Q000187:drug effects / Q000502:physiology* / Q000503:physiopathology; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology*
D018696:Neuroprotective Agents; D016194:Receptors, N-Methyl-D-Aspartate; D016291:Dizocilpine Maleate; D009538:Nicotine; D009020:Morphine