Modulatory effect of two novel CGRP receptor antagonists on nasal vasodilatatory responses to exogenous CGRP, capsaicin, bradykinin and histamine in anaesthetised pigs

Sympathetic and Sensory-Motor Nerves in Peripheral Small Arteries

Small arteries, which play important roles in controlling blood flow, blood pressure, and capillary pressure, are under nervous influence. Their innervation is predominantly sympathetic and sensory motor in nature, and while some arteries are densely innervated, others are only sparsely so. Innervation of small arteries is a key mechanism in regulating vascular resistance. In the second half of the previous century, the physiology and pharmacology of this innervation were very actively investigated. In the past 10-20 yr, the activity in this field was more limited. With this review we highlight what has been learned during recent years with respect to development of small arteries and their innervation, some aspects of excitation-release coupling, interaction between sympathetic and sensory-motor nerves, cross talk between endothelium and vascular nerves, and some aspects of their role in vascular inflammation and hypertension. We also highlight what remains to be investigated to further increase our understanding of this fundamental aspect of vascular physiology.

Interaction of histamine and calcitonin gene-related peptide in the formalin induced pain perception in rats

Histamine and calcitonin gene-related peptide (CGRP) contribute to the pain perception. The aim of the present study is to clarify the interaction of histamine and CGRP in the perception of inflammatory pain. The effects of a histamine H1 receptor antagonist (pyrilamine, i.p.), an H2 receptor antagonist (ranitidine, i.p.) and a CGRP antagonist (CGRP 8-37, i.t.) on the formalininduced pain was studied in rats. Pyrilamine and ranitidine produced a dose-dependent antinociceptive response in the first and the second phases of the formalin test. A single administration of pyrilamine (1 mg/kg, i.p.), ranitidine (10 mg/kg, i.p.) or CGRP 8-37 (10 µg/µL, i.t.) had no significant effects on the pain perception in the second phase. A combination of CGRP 8-37 and pyrilamine or ranitidine at these sub-effective doses, however, showed nociceptive response in the second phase. Moreover, a histamine (i.t.)-induced hyperalgesia was completely prevented by treatment with GGRP 8-37 at this dose. Our findings have raised the possibility that the CGRP system has interaction with histamine in the perception of inflammatory pain.

Adrenomedullin level in the nasal discharge from allergic rhinitis cohort

Adrenomedullin (AM) is a potent hypotensive and vasodilatory peptide. AM may exert protective actions against the development of many diseases by modulating the blood circulation and body fluid balance. In addition to these functions, it has recently been reported to play important roles in the development of allergy and infections. The purpose of the present study was to demonstrate the existence of AM in the human nasal mucosa and to discuss whether AM might contribute to the pathogenesis of nasal congestion. We measured the total AM concentrations in the nasal discharge. The total AM concentration in the nasal discharge was significantly higher in the non-allergy group (72.1 ± 55.5 fmol/ml) than in the allergy group (37.1 ± 44.2 fmol/ml). By immunohistochemical examination, we identified AM-containing cells in the nasal mucosa from both subjects with and without nasal allergy, and also in nasal polyps. Moreover, those cells were positive for anti-tryptase antibody which recognizes mast cells. In nasal allergy, vasodilatation and increase in vascular permeability are characteristic features of the immediate phase response. Reduced AM levels in the nasal discharge may be associated with attenuation of both of these factors. On the other hand, immunohistochemical analysis demonstrated AM-immunoreactive cells in the chronic phase of rhinosinusitis. In the late and inflammatory phase, mast cells produce AM, which possibly acts as an inhibitor of inflammatory cell migration. In conclusion, AM may be actively secreted into the nasal discharge. AM in the nasal discharge may have protective and anti-inflammatory effects in the nasal mucosa.

Molecular cloning, functional characterization of the porcine transient receptor potential V1 (pTRPV1) and pharmacological comparison with endogenous pTRPV1

In the present study, we cloned a porcine orthologue of transient receptor potential V1 (pTRPV1) and heterologously expressed it in human embryonic kidney (HEK) 293 cells to characterize its pharmacological properties. At the amino acid level, pTRPV1 was highly homologous (83-90%) to other orthologues of TRPV1. The expression of receptors was examined with current and [Ca2+]i responses to capsaicin using whole-cell patch-clamp and fura-2 ratio imaging techniques, respectively, and by immunostaining with an anti-TRPV1 antibody. The receptors were characterized by changes in [Ca2+]i in response to various vanilloid agonists, low pH and heat and by the effects of TRPV1 antagonists on them. The various TRPV1 agonists activated pTRPV1 in a dose-dependent manner in the order of potency of resiniferatoxin (RTX) > olvanil > capsaicin > phorbol 12-phenylacetate 13-acetate 20-homovanillate (PPAHV), phorbol 12,13-dinonanoate 20-homovanillate (PDNHV). Isovelleral and scutigeral had no effect. Endogenous vanilloids (anandamide > 15 (s)-HPETE >> NADA), low pH and noxious heat (>42 degrees C) activated pTRPV1. Comparison of amino acid sequences with various mammalian TRPV1 homologues suggested some novel putative vanilloid recognition sites. TRPV1 antagonists, iodoRTX, ruthenium red and capsazepine suppressed capsaicin-induced responses. Similar to human TRPV1, but not rodent TRPV1, capsazepine was effective in blocking pH- and heat-induced responses. Similar pharmacological profiles were observed in cultured porcine dorsal root ganglion neurons. We discuss putative amino acid residues related to pharmacological differences among mammalian TRPV1 homologues.