The different patterns of maturation of the claustrocortical connections in a rabbit.

The quantitative analysis of the claustrocortical connections labeled with the fluorescent retrograde tracer Fluoro-Gold (FG) was conducted on 90 rabbits subdivided into the following age groups (P2, P7, P14, P21, P30, P60, P90, P120, P180). The equal volumes of retrograde fluorescent tracer FluoroGold (FG) were injected into the selected regions of the motor or somatosensory cortices. The volume of the dorsal part of the claustrum, total number of projecting neurons, numerical density and percentage distribution of projecting neurons were estimated by means of the unbiased stereological methods. The claustrocortical connections both with the motor and somatosensory areas in a rabbit are established in the postnatal life. The parts of the claustrum occupied by the motor and somatosensory projection zones as well as the morphology of the cortically projecting neurons do not reveal characteristic changes during the studied period. The significant decrease of the total number and numerical density of cortically projecting neurons as well as the increase of the claustral volume may reflect the process of adjustment of the claustrum to its modulatory function upon corresponding cortical areas. The intensity of the claustral connections with the motor and somatosensory cortices reveals significant difference during the studied period, being higher for the motor projection. It may be assumed that the claustrocortical connections established before birth undergo significant quantitative changes during postnatal development.