The role of hypophyseal and adrenal mechanisms in the hypoalgesic response to non-contingent food delivery in the rat

Exposure to non-contingent food delivery has been shown to elicit an increase in nociceptive thresholds in rats. This hypoalgesia has previously been shown to be reversible by the opiate antagonist naloxone. Given that most opioid forms of SIA are found to rely on an intact pituitary-adrenal axis, this research examined the possibility that the hypoalgesic response to non-contingent food delivery is also hormonally mediated. Hypophysectomy (Expt. 1) but not bilateral adrenalectomy (Expt. 2) was found to completely attenuate the hypoalgesic response to non-contingent food delivery. Preliminary data from ongoing research is presented that points to the possible involvement of the hypophyseal peptides β-endorphin and adrenocorticotropin hormone (ACTH).