Reference

Possible involvement of capsaicin-sensitive sensory nerves in the regulation of intestinal blood flow in the dog

Possible involvement of capsaicin-sensitive sensory nerves in the regulation of intestinal blood flow in the dog. Rozsa, Zsuzsa; Jancso, G.; Varro, V. (First Dep. Intern. Med., Univ. Med. Sch., Szeged H-6701, Hung.). Naunyn-Schmiedeberg's Arch. Pharmacol., 326(4), 352-6 (English) 1984. CODEN: NSAPCC. ISSN: 0028-1298. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) Capsaicin [404-86-4] injected into the superior mesenteric artery in dogs evoked a marked dose-dependent increase in mesenteric blood flow in the dose range of 0.1-7 mg/kg. The intestinal vasodilatory effect of capsaicin were invariably demonstrated after pretreatment with adrenoceptor and dopamine receptor antagonists, as well as with the ganglion blocking agent hexamethonium. Pretreatment with atropine reduced, but did not abolish, the increase in intestinal blood flow elicited by capsaicin. Concomitant administration of somatostatin [51110-01-1] inhibited both the atropine-sensitive and atropine-resistant components of the effect of capsaicin. Apparently, the intestinal vasodilatory effect of capsaicin are mediated by substance P [33507-63-0] release from capsaicin-sensitive paravascular nerve fibers assocd. with the blood vessels of the gastrointestinal tract. Sensory substance P-contg. nerve fibers may be involved in the regulation of the vascular reactions of the gut.

Capsaicin and bradykinin-induced substance P-ergic responses in the iris sphincter muscle of the rabbit

Capsaicin and bradykinin-induced substance P-ergic responses in the iris sphincter muscle of the rabbit. Ueda, Naoko; Muramatsu, Ikunobu; Fujiwara, Motohatsu (Fac. Med., Kyoto Univ., Kyoto 606, Japan). J. Pharmacol. Exp. Ther., 230(2), 469-73 (English) 1984. CODEN: JPETAB. ISSN: 0022-3565. DOCUMENT TYPE: Journal CA Section: 2 (Mammalian Hormones) Exogenously applied capsaicin [404-86-4] and bradykinin [58-82-2] produced contractile responses in the rabbit iris sphincter muscle and responses were remarkably suppressed by [D-Pro2,D-Trp7,9]-substance P, a substance P [33507-63-0] antagonist, and disappeared in trigeminally denervated prepns. Repetitive application of capsaicin or bradykinin produced a gradual decline in the responses, thereby indicating the development of tachyphylaxis. Furthermore, bradykinin failed to induce any response after the development of capsaicin-induced tachyphylaxis, but after the development of tachyphylaxis to bradykinin, responses to capsaicin persisted. Elec. transmural stimulation produced cholinergic and substance Pergic responses in the rabbit iris sphincter muscle. Substance Pergic response to elec. transmural stimulation also was abolished after development of tachyphylaxis to capsaicin, but not to bradykinin. The contractile response to exogenously applied substance P was not affected by the development of tachyphylaxis to capsaicin and bradykinin. Evidently, capsaicin and bradykinin produce substance Pergic contractile responses mediated by the trigeminal nerve and the mechanisms of action differ between the 2 drugs. These effects of capsaicin and bradykinin are discussed in relation to occurrence of neurogenic inflammation in the eye.