1. Effect of PG-SPI and PG-KII, two novel and natural tachykinins, on salivary secretion in the rat
M Broccardo, G Improta, A Brandoni, A Tabacco Peptides. 1996;17(4):729-31. doi: 10.1016/0196-9781(96)00052-6.
In an in vivo study of salivation in rats, the scialogogic effects of two natural and amphibian tachykinins, PG-SPI and PG-KII, which activate distinct tachykinin receptors, were compared with those of the tachykinins substance P, neurokinin A and B, and kassinin. The rank order of potencies of these peptides injected intravenously on salivation was: PG-SPI = SP > or = PG-KII = KASS > NKA > > NKB. Atropine (1 mg/kg. i.v.) had no effect on PG-SPI-, SP-, and NKA-induced salivation, but reduced that stimulated by PG-KII and KASS. We conclude that PG-SPI and PG-KII increase salivary secretion through different mechanisms and that rat salivary glands contain PG-SPI-and PG-KII-sensitive receptors.
2. Parallel bioassay of PG-SPI, an amphibian acidic SP-like peptide, mammalian basic substance P, and neurokinins A and B on in vitro and in vivo test systems
M Broccardo, G Improta, C Severini Peptides. 1995;16(4):609-14. doi: 10.1016/0196-9781(95)91323-6.
In vitro and in vivo test systems were used to compare the biological activities of substance P and the neurokinins A and B with those of a newly isolated substance P-like acidic peptide, PG-SPI (pGlu-Pro-Asn-Pro-Asp-Glu-Phe-Phe-Gly-Leu-Met-NH2). On nearly all the isolated smooth muscle preparations tested, PG-SPI appeared only slightly more potent than SP, but on guinea pig trachea it was 50 times more potent. The in vitro spasmogenic effect of PG-SPI on guinea pig trachea was inhibited by the NK1 receptor antagonist, CP 96,345. In in vivo tests, intracerebroventricularly injected PG-SPI was about 20 times more potent than SP in inhibiting gastric acid secretion and emptying in rats. Tests with antagonists showed that CP 96,345 reduced PG-SPI-induced inhibition of gastric emptying and the NK2 receptor antagonist, MEN 10,376, sharply blocked PG-SPI-induced inhibition of gastric acid secretion. These findings fit poorly into the current classification of tachykinin receptors and suggest that the acidic substance P-like peptide is a valuable tool for studying the functional role of other tachykinin receptor subtypes.
3. Effects of supraspinal administration of PG-SPI and PG-KII, two amphibian tachykinin peptides, on nociception in the rat
G Improta, M Broccardo Peptides. 2000 Nov;21(11):1611-6. doi: 10.1016/s0196-9781(00)00292-8.
We investigated and compared the effects of two amphibian tachykinins, the NK1 receptor agonist PG-SPI and the NK3 receptor agonist PG-KII, and the mammalian tachykinins substance P, neurokinin A and neurokinin B on the reaction time to a painful radiant heat stimulus (tail-flick test in rats) after intracerebroventricular injection. PG-SPI (1, 10 and 20 microg) and PG-KII (1, 5 and 10 microg) significantly increased the reaction time. Substance P (10 microg) injected intracerebroventricularly induced antinociception, whereas neurokinin A and neurokinin B did not. Like analgesia evoked by exogenous substance P, PG-SPI-evoked analgesia was blocked by pretreatment with naloxone. Naloxone left PG-KII antinociception unchanged, but the NK3 receptor selective antagonist markedly reduced it. These findings suggest NK1 and NK3 tachykinin receptor system involvement in supraspinal analgesia in rats.
