In the CNS, where Ca(2+) overload has been established as a mechanism contributing to neuronal damage associated with excitotoxicity, stroke and ischemia, there is interest in understanding the role of calpain inhibition in rescuing neurons from death. In these settings, the activation of large stores of latent calpain may rapidly lead to the demise of the neuron within hours. The activity of calpain is strictly regulated by calcium concentrations and interactions with calpastatin (endogenous calpain inhibitor). The interaction between calpains and calpastatin is calcium dependent, and little is known about the regulation of the neuronal calpain-calpastatin system in vivo. It has been postulated that calpastatin can be modulated by nerve growth factors (NGFs). We have demonstrated in vitro as well as in vivo a neuroprotective effect of the beta(2)-adrenoceptor agonist clenbuterol (CLN) mediated through an increased NGF expression. In this study we attempt to find out whether CLN is capable (1) of modulating proteolysis regulated by the calpain-calpastatin system and (2) of attenuating DNA-fragmentation induced by cerebral ischemia. Rats received CLN daily for 1 week, were then subjected to ischemia and finally perfused at different times post-ischemia. The proteolytic activity of calpain was measured by the immunolocalisation of calpastatin and spectrin-breakdown products (SBP). The time course of apoptosis was assessed by terminal dUTP nick end-labeling (TUNEL)-staining. CLN reduced CA1-hippocampal cell damage by 23%, attenuated DNA-laddering and decreased proteolysis of spectrin by enhancing calpastatin activity. These results provide evidence that CLN is a potent neuroprotective substance, which through the enhancement of calpastatin synthesis attenuates the apoptotic machinery and modulates proteolysis.