BACKGROUND: Based on the recent findings about the ability of sexual hormones to emit electrons (e(aq) (-)) and to act as electron mediator, it was of interest to investigate adrenaline as an important neurotransmitter. MATERIALS AND METHODS: Highest purity adrenaline (ADR) and chemicals were used for preparation of aqueous solutions (pH ~7.4). The excitation of ADR in singlet state was achieved by irradiation of airfree aqueous solution with monochromatic UV light at λ = 254 nm. The emitted "solvated electrons" (e(aq) (-)) were scavenged by chloroethanol, where the quantum yield of Cl(-) ions, Q(Cl(-))=Q(e(aq) (-)). ADR degradation and formation of photolytic products were followed by HPLC analysis. RESULTS AND CONCLUSION: It was found that Q(e(aq) (-)) values decrease with increasing ADR concentration: for 2.5×10(-5) mol/L ADR was determined as Q(e(aq) (-))=6×10(-3), whereas for 1×10(-3) mol/L ADR was found to be 0.9×10(-3). This is explained by formation of associates in ground state, which consume a part of emitted e(aq) (-). As a main photolytic product aminochrome was determined.