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Biomedical subjects

K M Hargreaves

Publications and source records attributed to K M Hargreaves.

At least 19 recordsLinked to original sources
PubMed2004

Neuropeptide Y inhibits capsaicin-sensitive nociceptors via a Y1-receptor-mediated mechanism.

Neuropeptide Y (NPY) is expressed in certain primary afferent fibers, is up-regulated in response to tissue injury and is capable of inhibiting nociceptive behavior at the spinal level. However, the spinal mechanism(s) for NPY-evoked antinociception is unknown. In this study, we evaluated the hypothesis that agonists at the NPY Y1 receptor subtype (Y1-R) inhibit exocytosis from the capsaicin-sensitive class of nociceptors. Using in vitro superfusion of rat dorsal spinal cord slices, pre-treatment with the Y1-R agonist [Leu(31)Pro(34)]NPY significantly inhibited capsaicin-evoked release of immunoreactive calcitonin gene-related peptide with an EC(50) value of 10.6 nM. This inhibitory effect was concentration dependent, significantly attenuated by pre-treatment with the Y1 receptor antagonist BIBP3226 and reproduced by synthetic NPY. Examination of adult rat dorsal root ganglia using double immunofluorescent labeling revealed frequent co-localization of Y1 receptor immunoreactivity in vanilloid receptor type 1-immunoreactive neurons, indicating that Y1 agonists may directly modulate the capsaicin-sensitive class of nociceptors. Collectively, these results indicate that NPY is capable of inhibiting capsaicin-sensitive neurons via a Y1 receptor mechanism, suggesting the mechanisms for spinal NPY-induced antinociception is due, at least in part, to inhibition of central terminals of capsaicin-sensitive nociceptors.

Analgesics↗
PubMed2003

The effects of pregnancy and estrogen on the expression of calcitonin gene-related peptide (CGRP) in the uterine cervix, dorsal root ganglia and spinal cord.

Before parturition the uterine cervix undergoes a ripening process ("softens" and dilates) to allow passage of the fetus at term. The exact mechanism(s) responsible for cervical ripening are unknown, though a role for peptidergic sensory neurons is emerging. Previous work demonstrated that administration of substance P (SP) to ovariectomized rats caused events associated with cervical ripening, that production of SP in cervix-related dorsal root ganglion (DRG) is estrogen responsive, and that release of SP from neurons terminating in the cervix and spinal cord peaks prior to parturition. The present study was designed to test the hypothesis that calcitonin gene-related peptide (CGRP), a neuropeptide co-stored with SP in many sensory neurons, undergoes changes with pregnancy and hormonal environment. Immunohistochemistry, in situ hybridization, reverse transcriptase-polymerase chain reaction (RT-PCR) and radioimmunoassay (RIA) were used to investigate CGRP in L6-S1 DRG, spinal cord and cervix during pregnancy and the role of estrogen in CGRP synthesis. CGRP-immunoreactive primary sensory neurons expressed estrogen receptors (ER-alpha and ER-beta). In the cervix, CGRP concentrations decreased, but in the L6-S1 DRG and the spinal cord segments, CGRP levels increased, with peak effects observed at day 20 of gestation. CGRP mRNA synthesis increased in DRG over pregnancy. Sensory neurons of ovariectomized rats treated with estrogen showed increased CGRP mRNA synthesis in a dose-related manner, an effect blocked by the ER antagonist ICI 182 780. From these results, we postulate that synthesis of CGRP in L6-S1 DRG and utilization in the cervix increase over pregnancy and this synthesis is the under influence of the estrogen-ER system. Collectively, these data are consistent with the hypothesis that CGRP plays a role in cervical ripening and, consequently in the birth process.

Animals↗
PubMed2003

The neuronal distribution of cannabinoid receptor type 1 in the trigeminal ganglion of the rat.

Cannabinoid compounds have been shown to produce antinociception and antihyperalgesia by acting upon cannabinoid receptors located in both the CNS and the periphery. A potential mechanism by which cannabinoids could inhibit nociception in the periphery is the activation of cannabinoid receptors located on one or more classes of primary nociceptive neurons. To address this hypothesis, we evaluated the neuronal distribution of cannabinoid receptor type 1 (CB1) in the trigeminal ganglion (TG) of the adult rat through combined in situ hybridization (ISH) and immunohistochemistry (IHC). CB1 receptor mRNA was localized mainly to medium and large diameter neurons of the maxillary and mandibular branches of the TG. Consistent with this distribution, in a de facto nociceptive sensory neuron population that exhibited vanilloid receptor type 1 immunoreactivity, colocalization with CB1 mRNA was also sparse (<5%). Furthermore, very few neurons (approximately 5%) in the peptidergic (defined as calcitonin gene-related peptide- or substance P-immunoreactive) or the isolectin B4-binding sensory neuron populations contained CB1 mRNA. In contrast, and consistent with the neuron-size distribution for CB1, nearly 75% of CB1-positive neurons exhibited N52-immunoreactivity, a marker of myelinated axons. These results indicate that in the rat TG, CB1 receptors are expressed predominantly in neurons that are not thought to subserve nociceptive neurotransmission in the noninjured animal. Taken together with the absence of an above background in situ signal for CB2 mRNA in TG neurons, these findings suggest that the peripherally mediated antinociceptive effects of cannabinoids may involve either as yet unidentified receptors or interaction with afferent neuron populations that normally subserve non-nociceptive functions.

Animals↗
PubMed2003

beta 2-Adrenoceptor regulation of CGRP release from capsaicin-sensitive neurons.

Previous studies have suggested that neurotransmitter substances from the sympatho-adrenomedullary system regulate pulpal blood flow (PBF), in part, by the inhibition of vasoactive neuropeptide release from pulpal sensory neurons. However, no study has evaluated the role of beta-adrenoceptors. We evaluated the hypothesis that activation of beta-adrenoceptors inhibits immunoreactive calcitonin gene-related peptide (iCGRP) release from capsaicin-sensitive nociceptive neurons via in vitro superfusion of bovine dental pulp. Either norepinephrine or epinephrine inhibited capsaicin-evoked iCGRP. The norepinephrine effect was blocked by the selective beta(2)-adrenoceptor antagonist, ICI 118,551, but not by pre-treatment with the selective beta(1)-adrenoceptor antagonist, atenolol. In addition, application of albuterol, a selective beta(2)-adrenoceptor agonist, significantly blocked capsaicin-evoked release of iCGRP. Collectively, these studies demonstrate that activation of beta(2)-adrenoceptors in dental pulp significantly reduces exocytosis of neuropeptides from capsaicin-sensitive nociceptors. This effect may have physiologic significance in regulating PBF. Moreover, since capsaicin selectively activates nociceptors, beta(2)-adrenoceptor agonists may have clinical utility as peripherally acting therapeutics for dental pain and inflammation.

Adrenergic Agents↗
PubMed2003

Intrinsic regulation of CGRP release by dental pulp sympathetic fibers.

Neurotransmission from sympathetic and peptidergic afferent fibers participates in the regulation of pulpal blood flow (PBF) via opposing effects. In this study, we directly tested the hypothesis that activation of pulpal sympathetic terminals inhibits exocytosis of immunoreactive calcitonin gene-related peptide (iCGRP) from peptidergic afferents innervating bovine dental pulp. The results demonstrate that norepinephrine inhibits capsaicin-evoked iCGRP release. The application of alpha-adrenergic antagonists (phentolamine or phenoxybenzamine) increased spontaneous release of iCGRP. Moreover, administration of agents that evoke the release of sympathetic neurotransmitters (guanethidine or reserpine) inhibited capsaicin-evoked iCGRP release. Collectively, these results indicate that sympathetic neurotransmission inhibits exocytosis from pulpal peptidergic afferent fibers. Analysis of these data supports the hypothesis that peripheral sympathetic vasomotor control may operate by a direct mechanism (vasoconstriction) as well as by an indirect mechanism (e.g., inhibition of exocytosis from afferent fibers). Since capsaicin-sensitive neurons are nociceptors, it is possible that certain sympathetic neurotransmission may modulate pain.

Adrenergic Fibers↗
PubMed2001

Capsaicin-evoked CGRP release from rat buccal mucosa: development of a model system for studying trigeminal mechanisms of neurogenic inflammation.

Many of the physiological hallmarks associated with neurogenic inflammatory processes in cutaneous tissues are similarly present within orofacial structures. Such attributes include the dependence upon capsaicin-sensitive sensory neurons and the involvement of certain inflammatory mediators derived therein, including calcitonin gene-related peptide (CGRP). However, there are also important differences between the trigeminal and spinal nervous systems, and the potential contributions of neurogenic processes to inflammatory disease within the trigeminal system have yet to be fully elucidated. We present here a model system that affords the ability to study mechanisms regulating the efferent functions of peptidergic terminals that may subserve neurogenic inflammation within the oral cavity. Freshly dissected buccal mucosa tissue from adult, male, Sprague-Dawley rats was placed into chambers and superfused with oxygenated, Krebs buffer. Serial aliquots of the egressing superfusate were acquired and analysed by radioimmunoassay for immunoreactive CGRP (iCGRP). Addition of the selective excitotoxin, capsaicin (10-300 microm), to the superfusion buffer resulted in a significant, concentration-dependent increase in superfusate levels of iCGRP. Similarly, release of iCGRP from the buccal mucosa could also be evoked by a depolarizing concentration of potassium chloride (50 mm) or by the calcium ionophore A23187 (1 microm). The specific, capsaicin receptor antagonist, capsazepine (300 microm), completely abolished the capsaicin-evoked release of iCGRP while having no effect whatsoever on the potassium-evoked release. Moreover, capsaicin-evoked release was dependent upon the presence of extracellular calcium ions and was significantly, though incompletely, attenuated by neonatal capsaicin denervation. Collectively, these data indicate that the evoked neurosecretion of iCGRP in response to capsaicin occurs via a vanilloid receptor-mediated, exocytotic mechanism. The model system described here should greatly facilitate future investigations designed to identify and characterize the stimuli that regulate the release of CGRP or other neurosecretory substances in isolated tissues. This system may also be used to elucidate the role of these mediators in the aetiology of inflammatory processes within the trigeminal field of innervation.

Animals↗
PubMed2001

Analgesic effects of peripherally administered opioids in clinical models of acute and chronic inflammation.

A series of double-blind, placebo-controlled clinical trials demonstrated that low doses of morphine (0.4, 1.2, and 3.6 mg) administered into the intraligamentary space of a chronically inflamed hyperalgesic tooth produced a dose-related naloxone-reversible analgesia. This analgesic effect is mediated by a local mechanism in the inflamed tissue, because subcutaneous administration of a 1.2 mg dose of morphine failed to elicit an analgesic response. In contrast, submucosal administration of 1.2 mg morphine or 50 microg fentanyl to the site of extraction of an impacted third molar after the onset of acute pain failed to elicit an analgesic response despite demonstration of a sensitive bioassay. These data indicate that peripheral opioid analgesia can be evoked in a model of chronic, but not acute, inflammatory pain, suggesting a temporal dependent mechanism needed for the expression of peripheral opiate analgesia during inflammation in humans.

Acute Disease↗
PubMed2001

Evaluation of functional GABA(B) receptors in dental pulp.

Gamma-aminobutyric acid (GABA) is an inhibitory neurotransmitter that is elevated in inflamed human dental pulp. Because GABA agonists are antihyperalgesic in other tissue, it is possible that GABA agonists have similar effects in dental pulp assuming that this tissue contains GABA receptors. We tested the hypothesis that dental pulp contains functional GABA(B) receptors using a GTPgamma35S binding assay. This is a functional assay because GTPgamma35S will be bound to cell membranes only when activation of metabotropic receptors has lead to binding and activation of their associated G(alpha)-proteins via release of GDP and binding of the GTPgamma35S. Baclofen, a GABA(B) agonist, evoked GTPgamma35S binding in both human and bovine dental pulp. This was mediated by the GABA(B) receptor because it was blocked by the selective antagonist phaclofen in both tissues. The presence of GABA and its receptor, GABA(B), suggests that this system may be relevant in the production or management of endodontic pain.

Animals↗
PubMed2001

Epidemiological evaluation of the outcomes of nonsurgical root canal treatment in a large cohort of insured dental patients.

Selected outcomes following initial nonsurgical root canal treatment (NSRCT) procedures were retrospectively assessed using an insurance company database of 110,766 nonsurgical root canal procedures that were completed by endodontists and their referring general dentists. A subset of 44,613 cases, with a minimum required follow-up time of 2 yr, showed incidences of extraction, retreatment and periradicular surgery equal to 5.56%, 2.47%, and 1.41%, respectively. The incidence of subsequent extraction increased with patient age. Teeth that were not restored after root canal therapy were significantly more likely to undergo extraction than restored teeth. Although the practice pattern for endodontists consisted of a significantly higher proportion of molars (48% more; p < 0.001) and a smaller proportion of anterior teeth (43% less; p < 0.001) than general dentists, both groups of providers had comparable rates of untoward events. These data strongly support the hypothesis that the specialist practice provides similar rates of clinical success compared with other providers, even when treating significantly more complex NSRCT cases. Overall, 94.44% of nonsurgical root canal treated teeth remained functional over an average follow-up time of 3.5 yr. These results are an important indication of the benefits of endodontic treatment when provided in an integrated health care delivery system of endodontists and their referring general dentists.

Adolescent↗
PubMed2000

Bradykinin levels in dental pulp by microdialysis.

Bradykinin is a potent mediator of pain and inflammation. To examine extracellular levels of bradykinin in human dental pulp, CMA/20 microdialysis probes were inserted into the pulp tissue of 22 teeth diagnosed with normal pulp or with irreversible pulpitis before their extraction or endodontic therapy. Probes were perfused with a modified Locke-Ringer's buffer and bradykinin levels in the dialysate evaluated using a radioimmunoassay. Mean extracellular levels of bradykinin within pulp tissue diagnosed with irreversible pulpitis were significantly higher (262.26 +/- 83.79 fmol/ml) than that found within normal pulp (19.41 +/- 6.47 fmol/ml). Highest levels of bradykinin were detected in pulp tissue diagnosed with irreversible pulpitis when the patient had reported pain in the past, compared with patients who were in pain just before their visit. These observations suggest that the bradykinin system is activated during pulpitis and may contribute to pain and inflammation.

Bradykinin↗
PubMed2000

Prostaglandin E2 enhances bradykinin-evoked iCGRP release in bovine dental pulp.

Mediators produced during inflammation are responsible for hyperalgesia and expression of neurotransmitters and receptors in the nervous system. The production of bradykinin (BK) and the prostaglandins (PGs) may regulate initiation of pain. This study tested the hypothesis that BK and prostaglandin E2 (PGE2) have a positive interaction in evoking neurosecretion of immunoreactive calcitonin gene-related peptide (iCGRP). Bovine dental pulp was prepared and stimulated by the superfusion method with BK alone and in combination with PGE2. Kinin receptor antagonists to bradykinin-evoked release of iCGRP were also tested. Also tested was the hypothesis that dental pulp contains either the B1 or B2 or both BK receptors. Results showed that PGE2 enhanced BK-evoked iCGRP release by more than 50%. Western immunoblots revealed detectable B2 receptor protein with no detectable B1 receptor protein. We conclude that BK evokes iCGRP release from bovine dental pulp which is enhanced by a positive interaction with PGE2. Neurosecretion is evoked from isolated terminals of dental pulp fibers via the bradykinin B2 receptor-dependent mechanism.

Analysis of Variance↗
PubMed2000

Should we conduct a trial of distributing naloxone to heroin users for peer administration to prevent fatal overdose?

Heroin overdose is a major cause of death among heroin users, and often occurs in the company of other users. However, sudden death after injection is rare, giving ample opportunity for intervention. Naloxone hydrochloride, an injectable opioid antagonist which reverses the respiratory depression, sedation and hypotension associated with opioids, has long been used to treat opioid overdose. Experts have suggested that, as part of a comprehensive overdose prevention strategy, naloxone should be provided to heroin users for peer administration after an overdose. A trial could be conducted to determine whether this intervention improves the management of overdose or results in a net increase in harm (by undermining existing prevention strategies, precipitating naloxone-related complications, or resulting in riskier heroin use).

Australia↗
PubMed1999

Pulpal exposure alters neuropeptide levels in inflamed dental pulp and trigeminal ganglia: evaluation of axonal transport.

Dental pulp is richly innervated with neurons containing calcitonin gene-related peptide (CGRP) or substance P (SP). Prior studies have demonstrated that inflammation alters these pulpal neuropeptides. In this study, we used a radioimmunoassay to evaluate the specificity of this response and the contribution of axonal transport. Rat mandibular molars were exposed and immunoreactive CGRP (iCGRP) and immunoreactive SP were measured. At 7 to 14 days after exposure, both pulpal iCGRP (73%) and immunoreactive SP (135%) displayed peak increases above control levels. This response was somatotopically restricted, with no changes observed in contralateral (intact) molars, or in ipsilateral mandibular molars after exposure of maxillary molars. Transection of the inferior alveolar nerve on day 13 significantly reduced pulpal levels of iCGRP on day 14. Collectively, these studies indicate that pulpal inflammation evokes a selective alteration in neuropeptide levels, due at least in part to alterations in transport or synthesis of neuropeptides in the trigeminal ganglion.

Analysis of Variance↗
PubMed1999

Evaluation of the combination of flurbiprofen and tramadol for management of endodontic pain.

Effective management of endodontic pain represents a continuing challenge. In this study, we evaluated the efficacy of flurbiprofen and a novel centrally acting analgesic, tramadol, alone and in combination, for reducing pain in endodontic emergency patients. Patients (n = 49) were administered a local anesthetic and underwent pulpectomy. They were then administered, on a double-blind basis, either: (i) placebo (one capsule to start and then every 6 h); (ii) flurbiprofen (100 mg loading dose and then 50 mg every 6 h); (iii) tramadol (100 mg loading dose and then 100 mg every 6 h); or (iv) the combination of flurbiprofen and tramadol (as above). Pulpectomy combined with placebo medication resulted in a 50% reduction in pain by 24 h (p < 0.01). Patients treated with flurbiprofen and tramadol reported less pain, compared with placebo treatment at 6 and 24 h (p < 0.01 for both). These results suggest that a nonsteroidal anti-inflammatory drug/opiate combination, together with endodontic therapy, may be useful in the management of endodontic pain.

Analgesics, Opioid↗
PubMed1999

Activation of excitatory amino acid receptors in bovine dental pulp evokes the release of iCGRP.

The activation of excitatory amino acid (EAA) receptors within the central nervous system is associated with numerous centrally mediated phenomena, including hyperalgesia. However, relatively little is known about the peripheral mechanisms which these receptors may regulate when activated. This research evaluated the hypothesis that EAA receptors in bovine dental pulp activate a population of peptidergic sensory neurons as measured by the release of immunoreactive calcitonin gene-related peptide (iCGRP), a neuropeptide associated with neurogenic inflammation. In vitro superfusion of bovine dental pulp was used to evaluate the regulation of iCGRP secretion by the EAA receptor agonists AMPA, kainate, NMDA, and L-glutamate. Both AMPA and kainate stimulated the release of iCGRP in a concentration-dependent manner (AMPA EC50 = 0.27 +/- 3.3 nM; kainate EC50 = 3.2 +/- 1.1 microM). Pre-treatment and co-administration of the AMPA/kainate receptor antagonist CNQX significantly reduced the iCGRP release evoked by either of these agonists. In contrast, neither NMDA nor L-glutamate induced any consistent changes in iCGRP release. These results suggest that the activation of AMPA and kainate receptors in dental pulp may contribute to peripheral release of vasoactive neuropeptides which mediate a neurogenic component of inflammation.

6-Cyano-7-nitroquinoxaline-2,3-dione↗
PubMed1999

Pain after periodontal scaling and root planing.

BACKGROUND: Although periodontal scaling and root planing, or SRP, is one of the most common procedures used in dental practice, there is little information available about the degree of postprocedural pain associated with it. The authors undertook this study to document the intensity and duration of pain after SRP with a view toward helping practitioners and their patients manage postprocedural discomfort. METHODS: Using the Heft-Parker self-assessment pain scale, 52 adults with moderate periodontitis evaluated their pain before and after SRP conducted with local anesthetic. RESULTS: After SRP, 28 percent of all patients reported faint-to-weak pain, 18 percent experienced weak-to-mild pain, 28 percent experienced mild-to-moderate pain, 8 percent had moderate-to-strong pain and 8 percent reported strong-to-intense pain. The average time to onset of maximum pain was approximately three hours after SRP, and the average duration of mild or greater pain was about six hours. Upon awakening the morning after SRP, subjects found that pain had returned to pre-SRP levels. Overall, 23 percent of all patients reported self-medicating with analgesics to relieve postprocedural pain. Women self-medicated earlier (P < .05) and more often than men (43 percent vs. 10 percent; P < .05). CONCLUSIONS: Patients experienced significant duration and magnitude of pain after SRP. This pain peaked between two and eight hours after SRP, lasted about six hours, and returned to pre-SRP levels by the morning after the procedure. Almost 25 percent of all patients self-medicated to relieve pain after SRP, and women took analgesic medication earlier and more often than men. CLINICAL IMPLICATIONS: Practitioners should consider using appropriate analgesic drugs to alleviate mild-to-moderate pain after SRP. On the basis of this study, it would appear that an analgesic that has a peak effect two to eight hours after the completion of SRP would be the most appropriate medication. Moreover, it is unlikely that analgesic medication would be needed by most patients beyond the day on which SRP was performed.

Adolescent↗