ABSTRACT-The present study was conducted to establish a new mouse model of dry skin pruritus. The rostral back was treated daily with cutaneous application of acetone /ether (1:1) mixture (AE), water following AE (AEW), 1% sodium lauryl sulfate (SLS) or tape stripping (TS). On the day after 5-day treatment, although all four treatments significantly decreased stratum corneum (SC) hydration and increased transepidermal water loss (TEWL), only AEW treatment significantly increased spontaneous scratching. An increase in the frequency of TS produced the marked increase of TEWL, without significant effects on SC hydration and spontaneous scratching. In AEW-treated mice, changes in SC hydration and TEWL were marked in the initial 2-day period, while spontaneous scratching increased gradually from 3 days after starting the treatment. The degranulation of cutaneous mast cells was increased by SLS treatment but not by other treatments. There was no apparent difference in AEW-induced spontaneous scratching between mast cell-deficient mice (WBB6F1-W /W V ) and normal littermates (WBB6F1-+/+). Opioid antagonists, naloxone and naltrexone, (1 mg /kg, subcutaneously) significantly suppressed spontaneous scratching in AEW-treated mice. It is suggested that spontaneous scratching of AEW-treated mice is an itch-related response and a useful model for studying the mechanisms of dry skin pruritus.

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A water extract of licorice root inhibits granuloma angiogenesis in adjuvant-induced chronic inflammation (Phytother. Res., 5, 195. 1991). The present study has investigated the effects of licorice-derived compounds on granuloma angiogenesis. Isoliquiritin (0.31-3.1 mg/kg), a licorice-derived flavonoid, inhibited the carmine content of granuloma tissue 50-fold greater than licorice extract. Glyeyrrhizin (20-80 mg/kg), a licorice-derived saponin, inhibited carmine content with a weak potency. The licorice extract (0.01-1 mg/ml) also inhibited tube formation from vascular endothelial cells in a concentration-dependent manner. From the chemical structure-activities of used licorice-derived flavonoids (0.1-100 microM), their potencies for anti-tube formation were in the order isoliquiritigenin > isoliquiritin > liquiritigenin >> isoliquiritin-apioside. Glycyrrhizin (0.1-100 microM) and glycyrrhetinic acid (0.1-10 microM) increased tube formation. A glycyrrhizin (82 micrograms/ml)-induced increase in tube formation was inhibited by isoliquiritin. The combined effect of a mixture of 82 micrograms/ml glycyrrhizin and 4.2 micrograms/ml isoliquiritin, a similar concentration ratio to their yield ratio in the licorice extract, corresponded to the effect of 100 micrograms/ml extract. In conclusion, the anti-angiogenic effect of licorice extract depended on the anti-tube formation effect of isoliquiritin.

Ascidian tadpole larvae change swimming behavior during the course of development. The photic behavior of the larvae of Ciona intestinalis was monitored by a computerized cell-tracking system with a time resolution of 0.1 s. Newly hatched larvae swim at an average speed of 1.4 mm/s but show no response to light stimuli. The swimming speed of the larvae became slower (0.4 mm/s) 3 h after hatching and they were induced to swim more rapidly by a sudden decrease in light intensity 4 h after hatching. During the course of development, the maximal speed of swimming behavior increased with time until 8 h after hatching and then plateaued. The action spectrum for the step-down photophobic response of the larvae was determined at around 8 h after hatching and was fitted to Dartnall's nomogram with the absorbance maximum of the pigment located at 505 nm. These results suggest retinal proteins in the ocellus of the larvae are the photoreceptors for the photobehavior.