Effects of preweanling chronic naltrindole administration on stress-induced antinociceptive responses in rats.
The effect of a daily injection of the delta-selective opioid antagonist naltrindole (1 mg/kg), from birth to postnatal day 19, on the development of stress-induced-antinociception (SIA) and on the antinociceptive response to the mu-selective agonist alfentanil (65 microg/kg) in female rats was investigated. Functional blockade of the delta-receptor during the preweanling period markedly reduced the antinociceptive response to swim-stress in 25-day-old rats, and SIA was only mediated by delta-receptors at this age. In 20-day-old rats and in adults, SIA was predominantly mu-receptor mediated and unaffected by delta-receptor blockade. The lack of interference with mu-receptor function was confirmed as alfentanil responses were unaffected by preweanling naltrindole treatment. The data show independence of mu- and delta-receptors in the control of SIA during development and an impairment of delta- but not mu-mediated SIA after chronic delta-antagonist treatment.
Antelo
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Departamento de Biología Animal II, Facultad de Biología, Universidad Complutense, 28040, Madrid, Spain.
Fernández
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B
Kitchen
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Viveros
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D000375:Aging; D015760:Alfentanil / Q000494:pharmacology*; D000701:Analgesics, Opioid / Q000494:pharmacology; D000818:Animals; D000831:Animals, Newborn; D004334:Drug Administration Schedule; D005260:Female; D009271:Naltrexone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D010146:Pain / Q000503:physiopathology*; D051381:Rats; D017208:Rats, Wistar; D017465:Receptors, Opioid, delta / Q000037:antagonists & inhibitors; D017450:Receptors, Opioid, mu / Q000819:agonists; D013315:Stress, Psychological / Q000503:physiopathology*; D013550:Swimming
D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D017465:Receptors, Opioid, delta; D017450:Receptors, Opioid, mu; D015760:Alfentanil; D009271:Naltrexone; C055382:naltrindole