Geert Jan Sterk, Henk van der Goot and Henk Timmerman* ... Vrije Universiteit, Department of Pharmacochemistry, De Boelelaan 1083, 108 1 HV Amsterdam, The Netherlands Eingegangen am 30. September 1985 ... S,S'-Alkylenediisothioureas were found to show only weak agonistic or antagonistic H,-activity, de- pending on the length of the alkylene chain. Introduction of a substituent in the amidino parts of both isothiourea groups resulted in a complete loss of the agonistic ...