The antiserum against hpcal4 is produced in rabbits by immunization with recombinant mouse Hpcal4 containing a 6-his tag at the N-terminal. The antibody was evaluated for specificity and potency: a) by Biotin-Avidin labelling of cryostat-, vibratom- and paraffinsections of 4% paraformaldehyde fixed brains and b) by immunoblots. The product is a polyclonal antiserum against Hpcal4 (1), a calcium-binding protein of the sensor EF-hand family related to hippocalcin. This antiserum stains the brain in a characteristic, unique pattern (Fig. 1; see also www.brain-map.org). The antiserum reacts specifically with Hpcal4 in tissue originating from rodents as determined by immunoblots