Comparative studies of new thienothiazine derivatives on heart and smooth muscle preparations of guinea pigs

New thienothiazine derivatives which differ in their side chain on the nitr ogen atom of the thienothiazine molecule were studied in guinea pig papilla ry muscles and terminal ilea using isometric contraction force measurements . Compounds with a heterocyclic ring in their side chain like MS 57 (pyrrol idinylethylcarboxamide side chain), MS 58 (piperidinoethylcarboxamide side chain) and MS 55 (morpholinoethylcarboxamide side chain) had the most poten t negative inotropic effect on isolated papillary muscles. The relaxing eff ect on smooth muscle was more pronounced with compounds carrying an aromati c ring in their side chain like MS 25 (dimethoxyphenylethyl-N-aminopropiony l side chain), MS 24 (dimethoxyphenylethyl-N-methylaminoacetyl side chain) and MS 27 (dimethoxyphenyl-N-methylethylaminoethylcarboxamide side chain). Our results show a tissue selectivity of the thienothiazine compounds.