In vivo release of CCK-8 from the dorsal horn of the rat: Inhibition by DAGOL

There is evidence that CCK-8 may interact with opioids and that both systems are probably implicated in pain modulation. In order to elucidate this relationship we sought to examine factors governing the movement of CCK-8 from the spinal cord into the extracellular space. We report that CCK-8 like immunoreactivity, as measured by RIA, is released from the spinal cord of the rat in vivo, following potassium stimulation and by direct activation of high threshold peripheral afferents by stimulation of the sciatic nerve. Also, we show that CCK-8 release is inhibited by the μ-selective opioid receptor agonist DAGOL. Naloxone totally reversed the effect produced by DAGOL, implying an opiate mediated mechanism.