A series of 3,4-dihydro-2H-1,2,4-benzothiadiazine 1,1-dioxide derivatives were synthesized and evaluated for their activity as allosteric modulators of kainate-activated currents in primary cultures of cerebellar granule neurons. Substitution of different groups at the 3-position of the benzothiadiazine ring distinguished between positive and negative allosteric modulatory properties.