The present effects show that, in terms of formalin-induced nociception, PKG-I inhibition is as effective as PKG-I deficiency
The present effects show that, in terms of formalin-induced nociception, PKG-I inhibition is as effective as PKG-I deficiency. compound P-positive neurons and materials was significantly reduced. The paucity of compound P in laminae I-III may contribute to the reduction of nociception in PKG-I-/- mice and suggests a role of PKG-I in compound P synthesis. Fifteen microliters of a 5% formaldehyde remedy was injected into the s.c. space in the dorsal part of the right hind paw. The time spent licking the formalin-injected paw was recorded in 5-min intervals up to 45 min, starting right after formalin injection. The PKG-I inhibitor Rp-8-Br-cGMPS (Biolog Existence Sciences Institute, Bremen, Germany) was delivered onto the lumbar spinal cord by intrathecal injection as has been explained (19). The drug was dissolved in artificial cerebrospinal fluid (141.7 mM Na+/2.6 mM K+/0.9 mM Mg2+/1.3 mM Ca2+/122.7 mM Cl-/21.0 mM mM mM dextrose, bubbled with 5% CO2 in 95% O2 to adjust the pH to 7.2) and injected inside a volume of 5 l. The dose (50 nmol) was 1/10th of the dose previously found to reduce flinching behavior in rats (4, 15). Drug injection was performed in short isoflurane anesthesia 10 min before the injection of formalin. Mice were adapted to the test perspex chamber having a grid bottom for at least 30 min before baseline screening. Fifteen microliters of a 10 mg/ml zymosan (Sigma) suspension in PBS (0.1 M PBS, pH 7.4) was then injected into the plantar part of the right hind paw. Mechanical hyperalgesia was assessed before zymosan injection and then hourly up to 7 h after zymosan injection. The threshold to mechanical nociceptive stimuli was assessed by means of a punctuated activation by using von Frey hairs of different advantages (0.008, 0.02, 0.04, PKI-402 0.07, 0.16, 0.4, 0.6, PKI-402 1, 1.4, 2, 4, and 6 g; Stoelting). They were placed perpendicularly PKI-402 onto the plantar surface of the right or remaining paw and bent slightly to apply punctuated pressure. The stimuli were applied at five repetitions each and at increasing order until the paw was withdrawn and then at decreasing order until paw withdrawal halted. This up-and-down screening was repeated after a short rest. The geometric mean of uppermost (increasing screening) and least expensive (decreasing screening) test results was taken as the mechanical paw-withdrawal threshold (MPWT). These data were log-transformed, and the PKI-402 percent decrease of the withdrawal threshold was then calculated in relation to the baseline withdrawal threshold as: % decrease of MPWT = MPWT_baseline – MPWT_zymosan/MPWT_baseline100. After two baseline measurements 250 nmol of 8-Br-cGMP was injected into the subarachnoid space of the lumbar spinal cord in 5 l of artificial cerebrospinal fluid. The dose was 1/10th of the dose previously found to cause hyperalgesia in rats (15), i.e., it was equivalent to the rat dose on a per kilogram basis. Based on these earlier results, 250 nmol intrathecally can be considered as a high dose. (Observe and Fig. 4, which is definitely published as assisting information within the PNAS internet site, concerning a low dose of 8-Br-cGMP.) The mechanical nociceptive threshold was assessed at 5, 7.5, 10, 20, 30, PKI-402 40, 50, and 60 min after 8-Br-cGMP injection as explained above. Reactions of the right and remaining paw were identical. The percentage decrease of the MPWT was acquired after log transformation as explained above. A hot-plate test (temp, 52C; cut-off latency, 40 s; Sizzling Plate Rabbit Polyclonal to HRH2 FMI, F?hr Medical Tools, Seeheim/Ober-Beerbach, Germany; time resolution, 0.1 s) was performed to assess acute thermal nociception. The test was repeated three times for each mouse with a rest of 15 min in between, and the mean latency was.