No abstract

Previously, we demonstrated intrathecal administration of oxytocin strongly induced anti-hyperalgesia in male rats. By using an oxytocin-receptor antagonist (atosiban), the descending oxytocinergic pathway was found to regulate inflammatory hyperalgesia in our previous study using male rats. The activity of this neural pathway is elevated during hyperalgesia, but whether this effect differs in a sex-dependent manner remains unknown. We conducted plantar tests on adult male and female virgin rats in which paw inflammation was induced using carrageenan. Exogenous (i.t.) application of oxytocin exerted no anti-hyperalgesic effect in female rats, except at an extremely high dose. Female rats exhibited similar extent of hyperalgesia to male rats did when the animals received the same dose of carrageenan. When atosiban was administered alone, the severity of hyperalgesia was not increased in female rats. Moreover, insulin-regulated aminopeptidase (IRAP) was expressed at higher levels in the spinal cords of female rats compared with those of male rats. Oxytocin-induced anti-hyperalgesia exhibits a sex-dependent difference in rats. This difference can partially result from the higher expression of IRAP in the spinal cords of female rats, because IRAP functions as an enzyme that degrades oxytocin. Our study confirms the existence of a sex difference in oxytocin-induced anti-hyperalgesia at the spinal level in rats.

This paper reports a study of the bronchodilator effects of doses of the beta 2 agonist fenoterol and the muscarinic blocker ipratropium suitable for administering in combination as a standard dose of two discharges from a single metered-dose pressurised aerosol. In 12 middle-aged bronchitics who had already been shown to respond to both types of drug the combination was almost always a little (6% on average) more effective than either drug singly. It is possible that an equal or better effect could have been obtained if fenoterol or perhaps ipratropium had been given alone in an individually determined maximally effective dose.