Abstract: The present invention is a pyrazine derivative which has glutamate receptor antagonizing activity, represented by formula: ##STR1## wherein Z represents C or N, provided that two Zs are not N atoms at the same time; R.sup.1 represents: ##STR2## wherein ##STR3## represents ##STR4## R.sup.6 represents H or alkyl, and R.sup.7 and R.sup.8 represent each H, alkyl, nitro or phenyl, or alternatively R.sup.7 and R.sup.8 are combined together to represent butadienylene or 1,4-butylene; R.sup.2 and R.sup.3 represent each H, F, cyano, acyl, nitro, alkyl, morpholino or one of said species of R.sup.1 ; R.sup.4 and R.sup.5 represent each H, hydroxyl, alkyl, cycloalkyl, heterocycle, phenyl, or Y-substituted alkyl; Y represents hydroxyl, acyloxy, F-substituted methyl, cycloalkyl, tetrahydrofuryl, carboxyl, alkoxycarbonyl or ##STR5## R.sup.9 and R.sup.10 represent each H or alkyl, or alternatively R.sup.9 and R.sup.10 are combined together to represent a 5- or 6-membered cyclic group which may contain oxygen atom(s).

Abstract: An inner air-tube of a tire for bicycle, particular for racing cycle substantially composed of a thermoplastic urethane resin of a specific type. The urethane resin is comprised of a bifunctional polyol, a diisocyanate and a diol serving as a chain-propagating agent, the ratio by mole of the diisocyanate to a mixture of the bifunctional polyol and the diol being in the range of 1.05-1.10:1. The urethane resin of this type is readily after-crosslinked to improve its physical properties to a great extent.