Elsevier

Peptides

Volume 3, Issue 2, March–April 1982, Pages 203-206
Peptides

Brief communication
Effects of conditioned fear and environmental novelty on plasma β-endorphin in the rat

https://doi.org/10.1016/0196-9781(82)90052-3Get rights and content

Abstract

The levels of rat plasma β-endorphin-like immunoreactivity following a 30 min exposure to (1) an unfamiliar operant chamber, (2) an unfamiliar operant chamber providing a VI-5 second schedule of 3 mA, 1 sec footshocks, or (3) a familiar chamber providing no shocks, but previously paired with unavoidable shocks were compared to control values from animals left undisturbed in their familiar home cages. The shocked group showed ten-fold elevations of β-endorphin-like immunoreactivity compared to the undisturbed control animals, while conditioned rats showed a smaller two-fold elevation when re-exposed to a chamber in which they had previously been shocked. Two of five rats exposed merely to an unfamiliar chamber showed elevations, but there was no statistically reliable group effect. Such procedures may be useful for controlled and parametric studies of the mobilization of pituitary or brain pools of β-endorphin under conditions involving merely anticipation of pain rather than the actual activation of ascending nervous pain pathways.

References (31)

  • H. Akil et al.

    Stress-induced increase in endogenous opiate peptides: concurrent analgesia and its partial reversal by naloxone

  • H. Akil et al.

    β-endorphin immunoreactivity in rat and human blood: radioimmunoassay, comparative levels and physiological alterations

    Life Sci.

    (1979)
  • S. Amir et al.

    The role of endorphins in stress: evidence and speculations

    Neurosci. Biobehav. Rev.

    (1979)
  • E.R. Baizman et al.

    Experimental alterations of endorphin levels in rat pituitary

    Neuroendocrinology

    (1979)
  • R.J. Bodnar et al.

    Stress-induced analgesia: neural and hormonal determinants

    Neurosci. Biobehav. Rev.

    (1979)
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    This study was supported by USPHS Grant #MH 28485 from the National Institutes of Mental Health.

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