The Journal of pharmacology and experimental therapeutics
-
J. Pharmacol. Exp. Ther. · Feb 1993
Pulmonary antiallergic and bronchodilator effects of isozyme-selective phosphodiesterase inhibitors in guinea pigs.
The effectiveness of theophylline (aminophylline) in treating asthma may result in part from nonselective inhibition of multiple isozymes of cyclic nucleotide phosphodiesterase (PDE). The roles for inhibition of different PDE isozymes in the pulmonary antiallergic and bronchodilator effects of theophylline were investigated in anesthetized and ventilated guinea pigs by using the PDE-III-selective inhibitor Cl-930, the PDE-IV-selective inhibitor rolipram and the PDE-V-selective inhibitor zaprinast. Aminophylline, Cl-930 and rolipram inhibited aerosol ovalbumin-induced full [leukotriene (LT) + histamine] and LT-dependent bronchoconstriction, but zaprinast was inactive. ⋯ In contrast, Cl-930 failed to inhibit airway hyperreactivity, but produced substantial residual bronchodilation. The results indicate that PDE-IV inhibition produces pulmonary antiallergic effects in vivo, including the apparent inhibition of LT release, which may contribute to the antiasthmatic actions of theophylline. The results also support previous suggestions that PDE-III inhibition contributes to the bronchodilator effect of theophylline.
-
J. Pharmacol. Exp. Ther. · Feb 1993
Activation of kappa opioid receptors by U50488H and morphine enhances the release of substance P from rat trigeminal nucleus slices.
The modulation of the release of substance P (SP) from sensory primary afferents by activation of kappa opioid receptors is not only equivocal, but also contradictory. Thus, in the present study, we have determined the effect of nanomolar concentrations of the highly selective kappa opioid receptor agonist trans-(+)-3,4-dichloro-N-methyl-N-[2-91- (pyrrolidinyl)cyclohexyl]benzacetamide methane sulphonate (U50488H), as well as micromolar concentrations of moderately mu-selective agonist morphine, on K(+)-evoked SP release from rat trigeminal nucleus caudalis slices. U50488H (10-30 nM) and morphine (10-30 microM) increased K(+)-evoked SP release without stimulating basal SP release. ⋯ Enhancement of K(+)-evoked SP release induced by 30 nM U50488H and 30 microM morphine was blocked by the opioid receptor antagonists naloxone (30 nM; nontype selective) and norbinaltorphimine (3 nM; kappa selective), but not by N,N diallyl Tyr-Aib-Aib-Phe-Leu (0.3 microM; delta selective), naloxonazine (1 nM; mu 1 selective) or beta-funaltrexamine (20 nM; mu selective). These findings indicate that activation of at least one population of kappa opioid receptors increases the release of SP from trigeminal nucleus caudalis. Excitatory presynaptic kappa opioid receptors on SP-containing primary afferents may be involved in the hyperalgesia of inflammatory processes, the "anti-analgesic" effect of dynorphin and the paradoxical "analgesia" produced by low doses of naloxone.