Opioid Systems and Magnetic Field Effects in the Land Snail, Cepaea nemoralis

Accumulating evidence shows that magnetic fields can affect a variety of opioid-mediated behavioral and physiological functions. The idea that endogenous opioids are involved in the mediation of fundamental behavioral responses in invertebrates is also gaining support. Evidence exists for opioid involvement in the mediation of nociceptive and antinociceptive ("analgesic") responses of the land snail, Cepaea nemoralis, and other mollusks, in a manner comparable to that in vertebrates. Exposure to various magnetic stimuli, including weak 60 Hz magnetic fields, has significant inhibitory effects on exogenous opiate-induced analgesia and endogenous opioid-mediated nociceptive responses of Cepaea in a manner analogous to that described for vertebrates. These effects of the magnetic stimuli are evident under both laboratory and natural conditions and include disruptions of the day-night rhythms of opioid-mediated nociception. These similar effects in Cepaea and rodents raise the possibility of a phylogenetic continuity in the effects of magnetic fields on basic opioid-mediated biological responses.