Influence of acute or repeated restraint stress on morphine-induced locomotion: involvement of dopamine, opioid and glutamate receptors.
The development of restraint stress-induced sensitization to the locomotor stimulating effect of morphine (2 mg/kg i.p.) was investigated. In experiment 1, both a single restraint session (2 h) and a repeated restraint stress (2 h per day for 7 days), similarly enhanced the effects of morphine on motor activity. In experiment 2, we observed that this sensitization was prevented by administration of both D(1) and D(2) dopaminergic antagonist [SCH-23390 (0.5 mg/kg i.p.) and (+/-)-sulpiride (60 mg/kg i.p.)] 10 min prior to the stress session. In experiment 3, we showed that an opioid antagonist pretreatment [naltrexone (1 mg/kg i.p.) 10 min prior to stress session, suppressed the stress-induced sensitization after morphine administration. In experiment 4, pretreatment with a non-competitive antagonist of the N-methyl-D-aspartate (NMDA) type of glutamate receptors [(+)-MK-801 (0.1 mg/kg i.p.)], 30 min prior to the acute restraint session, prevented the development of sensitization to morphine. All these results suggest that: (1) sensitization to morphine on stimulating locomotor effect does not depend on the length of exposure to stress (acute vs. repeated); (2) stimulation of both D(1) and D(2) dopaminergic receptors is necessary for the development of restraint stress-induced sensitization to morphine; (3) an opioid system is also involved in this sensitization process; and (4) the stimulation of glutamatergic NMDA receptors is involved in this acute restraint-induced effect.
Departamento de Farmacología, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
Capriles Nancy
CN
del Rosario
Alejandra Maria
AM
Pacchioni
Liliana Marina
LM
Cancela
D000208:Acute Disease; D000818:Animals; D001552:Benzazepines / Q000494:pharmacology; D002908:Chronic Disease; D016291:Dizocilpine Maleate / Q000494:pharmacology; D018492:Dopamine Antagonists / Q000494:pharmacology; D065127:Dopamine D2 Receptor Antagonists; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D009271:Naltrexone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D009294:Narcotics / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D011954:Receptors, Dopamine / Q000187:drug effects*; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors; D017470:Receptors, Glutamate / Q000187:drug effects*; D016194:Receptors, N-Methyl-D-Aspartate / Q000037:antagonists & inhibitors; D011957:Receptors, Opioid / Q000187:drug effects*; D012149:Restraint, Physical; D013315:Stress, Psychological / Q000523:psychology*; D013469:Sulpiride / Q000494:pharmacology
D001552:Benzazepines; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D018691:Excitatory Amino Acid Antagonists; D009292:Narcotic Antagonists; D009294:Narcotics; D011954:Receptors, Dopamine; D017447:Receptors, Dopamine D1; D017470:Receptors, Glutamate; D016194:Receptors, N-Methyl-D-Aspartate; D011957:Receptors, Opioid; D009271:Naltrexone; D016291:Dizocilpine Maleate; D009020:Morphine; D013469:Sulpiride