Substance P, neurokinin A and neurokinin B in the ocular response to injury in the rabbit

Abstract

1 Substance P (SP) and neurokinin A-(NKA)/neurokinin B (NKB)-like immunoreactivity (LI) were measured by radioimmunoassay in extracts of the rabbit uvea. The iris-ciliary body complex contained 3-4 times more NKA/NKB-LI than SP-LI. Tachykinins are thought to mediate many of the responses to ocular injury in the rabbit. Their possible role in the miosis and breakdown of the blood-aqueous barrier (BAB) was studied in vitro and in vivo. 2 In vitro, NKA had a more short-lasting contractile effect on the sphincter pupillae muscle than either SP or NKB, but SP was more potent than the other two. The tachykinin antagonist, spantide, dose-dependently suppressed the response to electrical stimulation (by 90% at 10-4M) and to the three tachykinins. An antiserum against SP (no cross-reaction with NKA or NKB) greatly suppressed the response to SP (by 90%) as well as to electrical field stimulation (by 40%). The responses to NKA and NKB were unaffected. 3 In vivo studies revealed that SP was more potent than NKA and NKB as a miotic. SP evoked a moderate breakdown of the BAB at high doses while NKA and NKB were virtually inactive. 4 We conclude that besides SP other tachykinins might play a role in the mediation of miosis in the rabbit eye but, of the three peptides investigated, only SP can be of importance for the breakdown of the BAB.

Capsaicin evokes secretion of nasal fluid and depletes substance P and calcitonin gene‐related peptide from the nasal mucosa in the rat

“…In fact, SP is likely to be responsible for at least a part of the capsaicinevoked secretion because capsaicin was shown to release SP from such fibres in the nasal mucosa, in agreement with the findings by Lundblad et al (1985), and an antagonist of SP, (D-Pro2,D-Trp7' 9)_ SP, inhibited the capsaicin-evoked secretion in the present study. Antagonists of SP also antagonize other tachykinins, such as neurokinin A (NKA) (Beding-Barnekow et al, 1988). NKA occurs together with SP in sensory nerve fibres in the nasal mucosa (Sundler et al, 1985) and may be responsible for some of the effect of capsaicin.…”

Effects of ruthenium red and capsazepine on C‐fibres in the rabbit iris

“…The eyes were immediately taken out. The iris was cut in half and the two halves were mounted in separate tissue baths (37°C), containing 8 ml of modified Krebs solution (Beding-Barnekow et al, 1988). The solution was bubbled continuously with 93% 02 and 7% C02, giving a pH of 7.4.…”

“…This concentration of capsaicin was chosen to produce approximately 50% of the maximal response (Wang & Hakanson, 1992a). After the capsaicin-induced contraction had reached its maximum (usually within 10min), the preparation was washed with drug-free Krebs solution and allowed to rest for 1 h. The preparation was then exposed to a buffer solution containing 137.7mM KCI (but no NaCI) (Beding-Barnekow et al, 1988); the resulting contraction was used as an internal standard. Each preparation was exposed to one concentration of ruthenium red or capsazepine only.…”

Pharmacological Profiles of Muscarinic Receptors in the Longitudinal Smooth Muscle of Guinea Pig Ileum

“…On the basis of pharmacological analysis, Ueda et al (11) and Muramatsu et al (12) have proposed that NKA rather than SP is a possible transmitter for mediating such a contraction. Beding-Barnekow et al (8) have suggested that ETS of rabbit iris sphincter muscle results in simultaneous release of SP and NKA.…”

“…It has also been demonstrated that other members of the tachykinin family such as neurokinin A (NKA) and neurokinin B (NKB) are present in the iris sphincter mus cle of rabbits (7,8). Electrical transmural stimulation (ETS) of the isolated rabbit iris sphincter muscle pro duces a noncholinergic, nonadrenergic contraction that is inhibited by tetrodotoxin and tachykinin antagonists (2,(9)(10)(11)(12).…”