We previously reported that S100B, a 20kDa Ca²⁺ - binding homodimer, inhibited the post-infarct myocardial hypertrophic response mediated by ₁-adrenergic stimulation through the protein kinase C (PKC) signaling pathway. In the present study, we examined whether the same pathway induced the S100B gene, supporting the hypothesis that S100B is a feedback negative regulator of this pathway. We transfected cultured neonatal rat cardiac myocytes with a luciferase reporter gene driven by the maximal human S100B promoter and progressively shorter segments of this promoter sequentially deleted from the 5' end. We identified a basic promoter essential for transcription spanning 162 bp upstream of the transcription initiation site and positive (at -782/-162 and -6689/-4463) and negative (at -4463/-782) myocyte-selective regulatory elements. We showed that the basic and maximal S100B promoters were activated specifically by ₁-adrenergic agonists through the _1A-adrenergic receptor, but not by any other trophic hormonal stimuli. The activation of the S100B promoter was mediated through the PKC signaling pathway. Transcription enhancer factor 1 (TEF-1) and RTEF-1 (related to TEF-1) influenced transcription from the maximal, but not the basic, promoter implicating active MCAT elements upstream of the basic promoter. Acting in opposing fashions, TEF-1 trans-repressed the S100B promoter and RTEF-1 trans-activated the promoter. Our results suggest that ₁-adrenergic stimulation induces the S100B gene following myocardial infarction through the PKC signaling pathway and that this induction is modulated by TEF-1 and RTEF-1.