Neuropeptide Y (NPY) potently inhibits pain neurons in rats, but does this occur in human
pain neurons? This hypothesis will be tested using microdialysis probes in patients who
elect to have root canal treatment or extraction of thier tooth.
The ongoing studies in rats indicate that a sympathetically-derived neuropeptide,
neuropeptide Y (NPY), potently inhibits the activity of the capsaicin-sensative class of
nociceptors (i.e., "pain" neurons). It is not know whether these results, generated from
rodent studies, occur in human tissues under normal or inflamed conditions. We plan to test
the hypothesis that NPY inhibits the initiation of neurogenic inflammation, as measured by
reduced release of substance P, from capsaicin-sensitive class of petidergic neurons
innervating normal and inflamed dental pulp. Such actions would be physiologically and
clinically significant, since inhibition of exocytosis from peripheral terminals of
nociceptive primary afferent fibers would likely alter neurogenic inflammation, local
vasodilation and , possibly pain. Our research strategy takes advantage of a uniquely
innervated tissue: dental pulp. Application of any physiologic stimulus to human dental
pulp, including thermal, osmotic, chemical or mechanical, produces only pain. Thus,
virtually all sensory neurons that innervate pulp appear to be nociceptors. Accordingly,
application of drugs to pulpal sensory neurons targets a population of sensory neurons
consisting predominantly of nociceptors.
The research questions are as follows:
1. Determine the capsaicin concentration-response curve from evoking the release of
immunioreactive substance P (iSP) from normal and inflamed dental pulp.
2. Determine the effect of NPY on altering basal and capsaisin-evoked release of iSP from
normal and inflamed dental pulp.
We will evaluate the hypothesis that NPY inhibits capsaicin-sensitive neurons in humans
using microdialysis probes implanted into anesthetized dental pulp, with release of
immunoreactive substance P (iSP) as our dependent measure. This study will include patients
who have elected to have a root canal procedure performed or to have a tooth extracted.
- teeth with diagnosis of normal pulp or irreversible pulpitis
- mandibular teeth
- indication for either root canal or extraction of tooth
- age between 18-50
- history of taking steroids within the last month
- history of hyperthyroidism, hypertension, asthma, uncontrolled or complicated Type-2
diabetes, drug abuse
- age less than 18 or greater than 50
- maxillary teeth