A peptide having an ED 50 of less than 500 nm, in particular 10 nM to an antibody which recognizes an epitope on an extracellular ±1 loop 2 or ²2 loop1 of a human adrenoceptor wherein the antibodys binding to the epitope results in an increase of ³-secretase activity, an increased release of ²-amyolid molecules and/or cellular dysfunction of cerebral blood vessel cells, glia cells or neurons, wherein the ED 50 value is measured by bioassay.
