The invention relates to compounds of the formula (I) and pharmaceutically usable derivatives, salts, solvates and stereoisomers and mixtures thereof, in which X, Y, Z, R1, R3, R4, R8, p, k, E, G, Z and Q are as defined in claim 1, which are employed as excitatory amino acid antagonists for combating neurodegenerative diseases, including cerebrovascular diseases, epilepsy, schizophrenia, Alzheimer's, Parkinson's or Huntington's disease, cerebral ischaemia, infarction or psychoses.