1662 Delta Opioids Stimulate iSP Release from Isolated Human PDL Neurons
J. ADCOCK, V. BINGHAM, C. TURNER, S. LEUNE, X. SUN, K. KEISER, and K. HARGREAVES, University of Texas San Antonio / Health Science Ctr, USA

Objective: Pulpal necrosis often leads to inflammation and sprouting of neurons terminating in the inflamed periradicular tissue. However, few studies have characterized the pharmacology of isolated human periradicular nociceptors. In this study, we tested the hypothesis that application of a delta opioid agonist activates peripheral human PDL neurons, as measured by the evoked release of immunoreactive substance P (iSP) from superfusates of isolated human apical root PDL neurons. Our secondary hypothesis was that clinical inflammation altered this effect. Method: Following informed consent, healthy teeth with fully formed apices, or teeth with necrotic pulp tissue and chronic apical periodontitis (CAP), were extracted; the apical 6mm of root was resected and placed in Hanks buffer. After baseline superfusate collection, either a test opioid (0.0-10uM) or vehicle (N=6-8/group) were administered for 20 min. iSP were measured by RIA and data analyzed by ANOVA. Results: The administration of a delta (DPDPE) opioid agonist, but not a mu (DAMGO), or kappa (U60,593) opioid agonist, evoked iSP release (p<0.01) with ~200% release over baseline rates at 10 uM. The delta opioid evoked similar iSP release from apices of control teeth and from apices of teeth with pulpal necrosis and CAP. Conclusions: These studies demonstrate that acute administration of delta opioids activates peripheral terminals of human PDL nociceptors under both control and inflamed conditions. Since these delta agonsits can inhibit iSP release evoked by bradykinin/PGE2 (Leune et al., 2004), these results indicate that delta receptor activation modulates peripheral neuronal activity by a multifactorial mechanism. Supported in part by P01 DA16719 (KMH), an AADR student research fellowship (SL, CT) and the CO*STAR training program (T32DE14318).

Seq #194 - Pulpal Blood Flow and Innervation, Dentinal Fluid, Neuropeptides, and Pain
10:15 AM-11:30 AM, Friday, 12 March 2004 Hawaii Convention Center Exhibit Hall 1-2

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