, Volume 78, Issue 3, pp 230–233 | Cite as

Delayed effects of naloxone on responsiveness to environmental novelty in rats

  • R. J. Rodgers
Original Investigations


Two experiments were conducted to examine further the hypothesized involvement of endorphins in responsiveness to environmental novelty. In Experiment 1, rats were treated with naloxone hydrochloride (0.5–5.0 mg/kg, SC) before initial exposure to a novel arena (Day 1) and then retested in the arena 24 h later (Day 2). Only naloxone (5 mg/kg) significantly affected Day 1 performance, producing a selective reduction in locomotor activity. However, compared to saline controls, all groups that had previously received naloxone showed marked reductions in both locomotor activity and rearing upon Day 2 retest. In Experiment 2, naloxone (0.5–5.0 mg/kg) was without significant effect on performance in naive animals which had been injected on Day 1 but not exposed to the arena until Day 2. These data suggest that the delayed effects of naloxone relate specifically to the initial experience of environmental novelty rather than receptor changes or metabolite influences resulting from acute antagonist treatment. Results are discussed in relation to a possible action of naloxone upon mechanisms of attention and/or memory.

Key words

Naloxone Endorphins Novelty Attention Memory Rats 


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  1. Amir S, Brown ZW, Amit Z (1980) The role of endorphins in stress: Evidence and speculations. Neurosci Biobehav Rev 4:77–87Google Scholar
  2. Archer J (1973) Tests for emotionality in rats and mice. A review. Anim Behav 21:205–235Google Scholar
  3. Arnsten AT, Segal DS (1979) Naloxone alters locomotion and interaction with environmental stimuli. Life Sci 25:1035–1042Google Scholar
  4. Bertolini A, Genedani S, Castelli M (1978) Behavioural effects of naloxone in rats. Experientia 34:771–772Google Scholar
  5. Blumberg H, Dayton HB (1972) Natoxone and related compounds. In: Kosterlitz HW, Collier HOJ, Villareal JA (eds) Agonist and antagonist actions of narcotic analgesics. Macmillan, London, pp 110–119Google Scholar
  6. Bodnar RJ, Kelly DD, Brutus M, Glusman M (1980) Stress-induced analgesia: A review of neural and hormonal mechanisms. Neurosci Biobehav Rev 4:87–100Google Scholar
  7. Gallagher M, Kapp BS (1978) Manipulation of opiate activity in the amygdala alters memory processes. Life Sci 23:1973–1977Google Scholar
  8. Grevert P, Goldstein A (1977) Some effects of naloxone on behaviour in the mouse. Psychopharmacology 53:111–113Google Scholar
  9. Hill RG (1981) The status of naloxone in the identification of pain control mechanisms operated by the endogenous opioids. Neurosci Lett 21:217–222Google Scholar
  10. Izquierdo I (1979) Effects of naloxone and morphine on various forms of memory in the rat: Possible role of endogenous opiate mechanisms in memory consolidation. Psychopharmacology 66:199–203Google Scholar
  11. Izquierdo I, Graudenz M (1980) Memory facilitation by naloxone is due to release of dopaminergic and beta-adrenergic systems from tonic inhibition. Psychopharmacology 67:265–268Google Scholar
  12. Jacob JJC, Ramabadran K (1978) Enhancement of a nociceptive reaction by opioid antagonists in mice. Br J Pharmacol 64:91–98Google Scholar
  13. Katz RJ, Gelbart J (1978) Endogenous opiates and behavioural responses to environmental novelty. Behav. Biol 24:338–348Google Scholar
  14. Martin WR (1967) Opiate antagonists. Pharmacol Rev 19:463–497Google Scholar
  15. Messing RB, Jensen RA, Martinez JL, Spiehler VR, Vasquez BJ, Soumireu-Morat B, Liang KC, McGaugh JL (1979) Naloxone enhancement of memory. Behav Neural Biol 27:266–275Google Scholar
  16. Olson GA, Olson RD, Kastin AJ, Coy DH (1981) Endogenous opiates 1980. Peptides 2:349–370Google Scholar
  17. Pert A, DeWald LA, Liao H, Sivit C (1979) Effects of opiates and opioid peptides on motor behaviours: Sites and mechanisms of action. In: Usdin E, Bunney E, Kline NS (eds) Endorphins in mental health research. Macmillan, London, pp 45–61Google Scholar
  18. Rodgers RJ, Deacon RMJ (1979) Effect of naloxone on the behaviour of rats exposed to a novel environment. Psychopharmacology 65: 103–105Google Scholar
  19. Roth KA, Katz RJ, Schmaltz K, Sibel M (1981) Reduced behavioural activity due to opiate blockade: Relations to stress. Int J Neurosci 12:59–62Google Scholar
  20. Sawynok J, Pinsky C, LaBella FS (1979) On the specificity of naloxone as an opiate antagonists. Life Sci 25:1621–1632Google Scholar
  21. Segal DS, Browne RG, Arnsten A, Derrington DC, Bloom FE, Davis AV, Gullemin R, Ling N (1979) Characteristics of beta-endorphin-induced behavioural activation and immobilization. In: Usdin E, Bunney E, Kline NS (eds) Endorphins in mental health research. Macmillan, London, pp 307–324Google Scholar

Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • R. J. Rodgers
    • 1
  1. 1.Postgraduate School of PsychologyUniversity of BradfordBradfordUnited Kingdom

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