EN
INTRODUCTION: Calbindin (CB) is one of the members of the EF-hand family of calcium-binding proteins which are involved in controlling intracellular calcium ion homeostasis. It may act as Ca2+ “fast” buffers and also as Ca2+ sensors. Intracellular calcium ions play an important role in immature and mature neurons. During early stages of development, calcium ions are involved e.g. in neuronal differentiation and plasticity, migration of neurons, or extension of neuronal processes. The preoptic area (POA) is a key structure which takes part in many autonomic functions (for example thermoregulation, thirst or hunger) as well as in reproduction and maternal behaviour, especially for pup retrieval as well as the onset of parental behaviour in females and males. AIM(S): The aim of the study was to examine the distribution of CB expression during the development of the preoptic area in the guinea pig by means of immunohistochemistry. METHOD(S): Brains from fetal stages (E50, E60), newborns (P0) and postnatal stages (P10, P20, P40, P100) were fixed in 4% paraformaldehyde in phosphate buffer and then cryoprotected. Frozen sections were processed for two immunohistochemical methods: an immunoenzymatic and immunofluorescence. RESULTS: Calbindin was highly expressed in the preoptic area of the male guinea pig, especially in the periventricular region. CB- immunoreactive (-ir) perikarya, fibers and punctate structures were observed at each examined stages. CB-ir perikarya were the most numerous at E50 and the least numerous at P100. The CB-ir neurons had oval, rounded or polygonal perikarya and some of them had processes of various length which emerged from perikarya. CB-ir fibers differed according to lengths. CONCLUSIONS: The highest expression of CB in the preoptic area at E50 coincides well with major developmental events (i.e. eyes opening) which in the guinea pig occur just before E50 stage.