A "good practice" approach to the quality and consistency of morphological examination of the internal head structures of the term rabbit fetus.

Variation in the interpretation of the regulatory guidelines has resulted in a diversity of techniques employed to examine the internal structures of the foetal rabbit head. Examination of the foetal rabbit brain, using a single transverse section as the sole technique, is considered not to be sufficiently thorough to be regarded as an adequate examination method. It is not compliant with published EPA and OECD guidelines covering required examination of the internal head structures, nor is it considered to conform to the spirit of the safety assessment required by the ICH guideline. Fixation of approximately half of the heads in each litter to allow the examination of multiple transverse sections enables the major structures within the head to be assessed effectively. This method is compliant with current guidelines, represents "good practice" and should be consistently adopted for the examination of the internal head structures of the term rabbit foetus.