BACKGROUND: Data is emerging in the human and invertebrate literature demonstrating that mu opiate receptors and morphine are present in cardiovascular tissues in diverse animals, including human tissues, where they may be exerting a cardioregulatory role via stimulation of constitutive nitric oxide (NO) production. MATERIAL/METHODS: NO release from lobster heart was evaluated without stimulation and after morphine exposure using a real-time NO-specific amperometric probe. In addition, real time NO release was evaluated after treatment with low doses of widely used pesticides (e.g., pyrethroids). Real time RT-PCR was used to investigate the presence of mu opiate receptor subtypes in lobster heart. RESULTS: Basal NO release occurs in lobster heart at the nanomolar level. Morphine enhanced this level of release; naloxone (an opiate antagonist) blocked it, as did exposure to the NO synthase inhibitor L-NAME. In addition, treatment with the pyrethroids, permethrin and resmethrin, abrogated constitutive NO release from lobster heart. Finally, by way of real time RT-PCR we were able to demonstrate the presence of the micro(3) opiate receptor subtype in lobster heart. CONCLUSIONS: Rhythmic NO bursts appear to be involved in normal cardiac muscle activity in Homarus americanus. Lobster heart contains morphinergic signaling components capable of slowing down its beating rate via NO production. In addition, compounds such as pyrethroid pesticides may alter normal cardiac activity by interfering with constitutive NO production and thus, depressing basal NO levels. This may ultimately make these animals more susceptible to environmental assaults/toxins.

Keywords: Feedback, DNA Primers - genetics, Base Sequence, Models, Biological, Myocardium - metabolism, Nephropidae - metabolism, Nitric Oxide - biosynthesis, Pesticides - toxicity, Pyrethrins - toxicity, Receptors, Opioid, mu - metabolism, Signal Transduction - drug effects