Qualitative and quantitative study of the postnatal development of the rabbit claustrum

The morphometric analysis of changes occurring in the rabbit claustrum in the early postnatal period was performed by means of unbiased stereological methods. Material consisted of 40 animals aged from P2 to P180 (P-postnatal day) divided into eight groups. The volume of the claustrum, total number and numerical density of its neurons change very rapidly at the beginning of the postnatal life and stabilize by about the fourth week.From the 21st postnatal day distribution and morphology of neurons correspond to that in adults. Almost from the beginning of the postnatal life the rabbit claustrum is composed of three different parts: anterior, central and posterior. The anterior part is the largest and it consists mainly of fusiform, pyramidal and multipolar neurons. The central part is generally composed of oval neurons. The posterior part is the smallest; the distribution of its neuronal types is similar to that in the anterior one.Rapid morphological changes of the claustrum and its neurons occurring during the first postnatal month seem to point out that this structure is able to fulfill its physiological role after this critical period.