seryl-leucyl-isoleucyl-glycyl--arginyl-leucinamide and Pain

Spatial and temporal cues govern the genesis of a diverse array of neurons located in the dorsal spinal cord, including dI1-dI6, dIL(A), and dIL(B) subtypes, but their physiological functions are poorly understood. Here we generated a new line of conditional knock-out (CKO) mice, in which the homeobox gene Tlx3 was removed in dI5 and dIL(B) cells. In these CKO mice, development of a subset of excitatory neurons located in laminae I and II was impaired, including itch-related GRPR-expressing neurons, PKCγ-expressing neurons, and neurons expressing three neuropeptide genes: somatostatin, preprotachykinin 1, and the gastrin-releasing peptide. These CKO mice displayed marked deficits in generating nocifensive motor behaviors evoked by a range of pain-related or itch-related stimuli. The mutants also failed to exhibit escape response evoked by dynamic mechanical stimuli but retained the ability to sense innocuous cooling and/or warm. Thus, our studies provide new insight into the ontogeny of spinal neurons processing distinct sensory modalities.

Topics: Animals; Animals, Newborn; Capsaicin; Cell Count; Chloroquine; Embryo, Mammalian; Ganglia, Spinal; Gastrin-Releasing Peptide; Gene Expression Regulation, Developmental; Homeodomain Proteins; Mice; Mice, Transgenic; Muscle Proteins; Neurons; Oligopeptides; Pain; Physical Stimulation; Protein Kinase C; Protein Precursors; Pruritus; Psychomotor Performance; Sensation; Somatostatin; Tachykinins; Vesicular Glutamate Transport Protein 1

Proteinase-activated receptor-2 (PAR2) and transient receptor potential vanilloid-1 (TRPV1) are co-localized in the primary afferents, and the trans-activation of TRPV1 by PAR2 activation is involved in processing of somatic pain. Given evidence for contribution of PAR2 to pancreatic pain, the present study aimed at clarifying the involvement of TRPV1 in processing of pancreatic pain by the proteinase/PAR2 pathway in mice.. Acute pancreatitis was created by repeated administration of cerulein in conscious mice, and the referred allodynia/hyperalgesia was assessed using von Frey filaments. Injection of PAR2 agonists into the pancreatic duct was achieved in anesthetized mice, and expression of Fos in the spinal cord was determined by immunohistochemistry.. The established referred allodynia/hyperalgesia following cerulein treatment was abolished by post-treatment with nafamostat mesilate, a proteinase inhibitor, and with capsazepine, a TRPV1 antagonist, in mice. Injection of trypsin, an endogenous PAR2 agonist, or SLIGRL-NH(2), a PAR2-activating peptide, into the pancreatic duct caused expression of Fos protein in the spinal superficial layers at T8-T10 levels in the mice. The spinal Fos expression caused by trypsin and by SLIGRL-NH(2) was partially blocked by capsazepine, the former effect abolished by nafamostat mesilate.. Our data thus suggest that the proteinase/PAR2/TRPV1 cascade might impact pancreatic pain, in addition to somatic pain, and play a role in the maintenance of pancreatitis-related pain in mice.

Topics: Acute Disease; Animals; Benzamidines; Capsaicin; Ceruletide; Disease Models, Animal; Gene Expression Regulation; Guanidines; Hyperalgesia; Male; Mice; Oligopeptides; Pain; Pancreatitis; Proto-Oncogene Proteins c-fos; Receptor, PAR-2; Spinal Cord; TRPV Cation Channels

Proteinase-activated receptor (PAR) 2 is expressed in a subset of primary afferent neurons and is involved in inflammatory nociception. The P2X3 ion channel is localized on nociceptors of sensory neurons. Using immunohistochemistry, we showed that many P2X3s are co-expressed with the PAR2 in rat dorsal root ganglia neurons. Nocifensive behavior induced by alphabeta-methylene adenosine 5'-triphosphate (ATP) injection to the hind paw was significantly augmented after the application of PAR2 agonists. Fos expression induced by the alphabeta-methylene ATP injection in dorsal horn neurons was also increased after the pre-application of PAR2 agonists. These findings indicate that PAR2 agonists may potentiate the sensitivity of P2X3 ion channel to noxious stimuli, and the interaction between PAR2 and P2X3 may be an important mechanism underlying inflammatory pain.

Topics: Adenosine Triphosphate; Animals; Behavior, Animal; Drug Synergism; Gene Expression; Immunohistochemistry; Male; Oligopeptides; Oncogene Proteins v-fos; Pain; Pain Measurement; Posterior Horn Cells; Rats; Rats, Sprague-Dawley; Receptor, PAR-2; Receptors, Purinergic P2; Receptors, Purinergic P2X3

Protease-activated receptors (PARs) 1 and 2 are expressed in capsaicin-sensitive sensory neurons, being anti- and pro-nociceptive, respectively. Given the possible cross talk between PAR-2 and capsaicin receptors, we investigated if PAR-2 activation could facilitate capsaicin-evoked visceral pain and referred hyperalgesia in the mouse and also examined the effect of PAR-1 activation in this model. Intracolonic (i.col.) administration of capsaicin triggered visceral pain-related nociceptive behavior, followed by referred hyperalgesia. The capsaicin-evoked visceral nociception was suppressed by intraperitoneal (i.p.) TFLLR-NH2, a PAR-1-activating peptide, but not FTLLR-NH2, a control peptide, and unaffected by i.col. TFLLR-NH2. SLIGRL-NH2, a PAR-2-activating peptide, but not LRGILS-NH2, a control peptide, administered i.col., facilitated the capsaicin-evoked visceral nociception 6-18 h after administration, while i.p. SLIGRL-NH2 had no effect. The capsaicin-evoked referred hyperalgesia was augmented by i.col. SLIGRL-NH2, but not LRGILS-NH2, 6-18 h after administration, and unaffected by i.p. SLIGRL-NH2, and i.p. or i.col. TFLLR-NH2. Our data suggest that PAR-1 is antinociceptive in processing of visceral pain, whereas PAR-2 expressed in the colonic luminal surface, upon activation, produces delayed sensitization of capsaicin receptors, resulting in facilitation of visceral pain and referred hyperalgesia.

Topics: Administration, Rectal; Animals; Behavior, Animal; Capsaicin; Colon; Dose-Response Relationship, Drug; Drug Synergism; Drug Therapy, Combination; Hyperalgesia; Injections, Intraperitoneal; Male; Mice; Oligopeptides; Pain; Pain Measurement; Peptides; Receptor, PAR-1; Receptor, PAR-2; Time Factors; Up-Regulation; Viscera

Proteinase-activated receptor 2 (PAR-2) is expressed on many nociceptive neurons. Application of PAR-2 agonists has been shown to induce behavioral signs of hyperalgesia. We investigated effects of the rat PAR-2 agonist SLIGRL-NH2 in the isolated rat skin-saphenous nerve preparation. SLIGRL-NH2 (100 microM) excited 20% of all C-fiber nociceptors tested. In addition, C-fiber nociceptors were sensitized to heat after SLIGRL-NH2 application resulting in an increase in response magnitude and a decrease of heat threshold. The PAR-2-inactive control peptide LRGILS-NH2 had no effect. The mechanical sensitivity of C-fibers was not affected by SLIGRL-NH2. PAR-2-mediated excitation and sensitization of primary nociceptors may contribute to PAR-2-mediated hyperalgesia.

Topics: Action Potentials; Animals; Dose-Response Relationship, Drug; Female; Hot Temperature; In Vitro Techniques; Nerve Fibers, Unmyelinated; Nociceptors; Oligopeptides; Pain; Pain Measurement; Pain Threshold; Physical Stimulation; Rats; Rats, Wistar; Receptor, PAR-2; Skin; Statistics, Nonparametric

We examined if thrombin or a receptor-activating peptide for protease-activated receptor-1 (PAR-1), a thrombin receptor, could modulate nociception at peripheral levels. Intraplantar administration of PAR-1 activators, thrombin or TFLLR-NH(2), but not its inactive control FTLLR-NH(2) or a PAR-2 activator SLIGRL-NH(2), significantly attenuated the hyperalgesia in rats treated with carrageenan, although they had no effect on nociception in naïve rats. The thrombin-PAR-1 system might thus act to attenuate nociception during inflammatory hyperalgesia.

Topics: Animals; Carrageenan; Dose-Response Relationship, Drug; Hyperalgesia; Male; Oligopeptides; Pain; Rats; Rats, Wistar; Thrombin; Time Factors

Protease-activated receptor-2 (PAR-2), a member of the G protein-coupled, seven trans-membrane domain receptor family, is activated by trypsin/tryptase and present in various tissues including the primary sensory neurons, playing a role in development of neurogenic inflammation. The present study examined if activation of peripheral PAR-2 could modulate nociception in the rat. Expression of mRNA for PAR-2 was confirmed in the L4-6 dorsal root ganglia, but not spinal cord. The PAR-2-activating peptide SLIGRL-NH2 administered by the intraplantar (i.pl.) route, produced thermal, but not mechanical, hyperalgesia in the rat, although the PAR-2-inactive control peptide LSIGRL-NH2 had no effect. Not only the PAR-2-activating but also inactive peptides elicited nociceptive behavior (licking/biting) in the intact rats, whereas only the former peptide produced such behavior in the rats that had received repeated administration of compound 48/80 for mast cell depletion. These data provide novel evidence that activation of peripheral PAR-2 is pro-nociceptive, producing thermal hyperalgesia and also triggering pain sensation, by itself, independently of mast cell degranulation.

Topics: Animals; Behavior, Animal; Ganglia, Spinal; Gene Expression; Hyperalgesia; Male; Neurons, Afferent; Nociceptors; Oligopeptides; Pain; Physical Stimulation; Rats; Rats, Wistar; Receptor, PAR-1; Receptor, PAR-2; Receptors, Thrombin; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Spinal Cord