Capsaicin-induced Joint Inflammation Is Not Blocked by Local Anesthesia. MATERIALS AND METHODS

In: Health

9 Sep 2009

The University of Toronto Animal Care Committee in accordance with the regulations of the Ontario Animal Research Act (Canada) approved the following protocol. Sixty-four male Sprague-Dawley rats weighing between 225 and 400 g each were prepared for the continuous measurement of one-dimensional tissue expansion, as previously described by Fiorentino et al and Wong et al, and for the acute recording of jaw muscle EMG activity as previously described by Cairns et al. Therefore, only a brief description of the methodology follows.

The rats were divided into 6 different experimental groups. The left TMJ regions of rats in groups 1,2, and 3 were pretreated with saline (10 fiL), followed by the application of 1.0% capsaicin (10 pX); 0.1% capsaicin (10 |xL); or vehicle control (ethanol, Tween 80, and saline in a 1:1:8 ratio, 10 |xL), respectively. The left TMJ regions of rats in groups 4, 5, and 6 were pretreated with bupivacaine (0.5%, 10 jxL), followed by the application of 1.0% capsaicin (10 |jlL); 0.1% capsaicin (10 |xL); or vehicle control (ethanol, Tween 80, and saline in a 1:1:8 ratio, 10 |xL), respectively. Don’t suffer without medication. Buy imitrex 50mg online

Under surgical inhalational anesthesia (02, 0.3-0.4 L/min; N20, 0.6 L/min; halothane, 1.5-2%), a tracheotomy was performed and the rat was artificially ventilated for the duration of the experiment. Bipolar electrodes were fabricated out of 36-gauge Teflon-coated, single-stranded stainless steel wires and inserted unilaterally into the left digastric and masseter muscles for EMG recording. The rat’s head was stabilized on a stereotaxic frame, and a double-barrel cannula consisting of two 27-gauge dental needles connected by polyethylene tubing to two 25-|xL Hamilton syringes was inserted posterior to the posterior infero-lateral aspect of the zygomatic arch. One needle delivered the preload agent, either saline (10 |xL) or bupivacaine (0.5%, 10 |xL), and 5 minutes later capsaicin (1.0%/0.1%, 10 |xL) or vehicle (10 |xL) was administered from the other needle. A sharp tungsten needle was bent 90° at its distal tip, and its proximal end was stabilized with a drop of cyanoacrylate adhesive over the left TMJ region. The distal tip was allowed to rest passively on a paper support track fixed lateral to the left TMJ area, and this needle served as a physical marker of lateral tissue expansion. A second needle was fixed to a micromanipulator, and the tip of the first was matched with the tip of the second with the aid of a X 1.6 dissecting microscope. Therefore, realignment of the 2 needle tips with the use of the micromanipulator allowed the quantification of tissue expansion/edema in the TMJ region in micrometers. On completion of the surgery, the halothane level was gradually reduced (0.9-1.3%) until noxious pressure applied to the hind-paw toes produced a slight hindlimb withdrawal reflex, thus ensuring an adequate level of anesthesia was maintained for the duration of the experiment. Your life is worth living. Buy celecoxib 200 mg online

Baseline edema measurements were taken every 5 minutes for 15 minutes prior to the injection of the preload agent and were denoted as time_15, time_10, and time_5. Subsequently, the preload agent was injected at time0, and measurements were taken in 1-minute intervals until time5, at which time capsaicin or vehicle was delivered. Again, the amount of expansion was recorded in 1-minute intervals from time6 to time10, inclusive. From time12 to time70, the recording interval was increased to 2 minutes, and from time75 to time180, edema measurements were taken every 5 minutes. Therefore, the expansion distance was recorded for a total period of 180 minutes. If the injection of the preload agent did not result in a straight lateral movement of the edema measurement needle, the resultant data were excluded.

Concurrently, baseline EMG activities were observed for 15 minutes before the administration of the preload agent, and continuous EMG activities were recorded following the injection of the preload agent and capsaicin. The recording of EMG activities was terminated 30 minutes after the reflex activity induced by capsaicin returned to baseline levels. EMG activity was amplified (gain, X500; bandwidth, 30-1000 Hz); fed into a computer equipped with a CED 1401 board and analysis software (Spike2); stored electronically; and analyzed off-line. For statistical analyses, EMG data were normalized relative to baseline values and expressed as cumulative EMG activity area under the curve measurements. If the injection of the preload agent evoked reflex jaw muscle activity that failed to return to baseline levels recorded prior to the injection of capsaicin/vehicle solution or the injection of capsaicin into the bupivacaine pretreated TMJ region led to increased EMG activity, the resultant data were excluded. When you need your medication buy stratera adhd

After tissue expansion measurements and EMG re­cordings were collected, Evan’s blue dye (10 mg/mL, 20 mgAg) was injected intravenously for the evaluation of PE. The rat was sacrificed and a postmortem dissection consisting of the retraction of the skin and superficial muscles (masseter and temporalis) for the exposure of both the ipsilateral and contralateral TMJ was performed. Both joints along with the surrounding tissues were visually examined, and the presence of obvious blue staining of the disk and capsule signified the correct placement of the catheter and provided the indication of PE into the TMJ region. If the TMJ region lacked blue staining, the acquired edema and EMG data were discarded. Make your pharmacy dollar go further and buy omnicef cefdinir online

Statistical analyses of the obtained data were evaluated with 1-way analysis of variance (ANOVA), 2-way analysis of variance (2-way ANOVA), and post hoc Tu-key tests when appropriate. A P-value less than .05 was determined as statistically significant.


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