Colocalization pattern of calbindin and cocaine- and amphetamine-regulated transcript in the mammillary body-anterior thalamic nuclei axis of the guinea pig

The study describes for the first time the colocalization pattern of calbindin (CB) and cocaine- and amphetamine-regulated transcript (CART) in the mammillary body (MB) and anterior thalamic nuclei (ATN) - structures connected in a topographically organized manner by the mammillothalamic tract (mtt). Immunohistochemical study was performed on fetal (E40, E50, E60), newborn (P0) and postnatal (P20, P80) brains of the guinea pig, but the coexistence pattern of the substances was invariable throughout the examined developmental stages. CB and CART colocalized in the perikarya of the lateral part of the medial mammillary nucleus (MMl), whereas in its medial part (MMm) only CB was detected. In the mtt, which originates from the MB, both the substances were present and colocalized in single fibers. Next, fibers from the mtt spread toward the ATN in a particular way: fibers containing CB ran to both the anteromedial thalamic nucleus (AM) and anteroventral thalamic nucleus (AV), while fibers containing CART ran mostly to the latter one. In the ventral part of AV, CB and CART colocalized vastly in the neuropil. The lateral mammillary nucleus and anterodorsal thalamic nucleus were virtually devoid of CB- and CART-positive structures. Based on the known connections between the MB and ATN, we conclude that the studied substances may cooperate in the MMl-AV part of the axis and CB plays a significant role in the MMm-AM part.

Embryonic and postnatal development of calcium-binding proteins immunoreactivity in the anterior thalamus of the guinea pig

Our recent studies have shown that the distribution of calretinin (CR) in the anterior thalamic nuclei (ATN) changes significantly during the development of the guinea pig. The present study was designed to reveal the distribution pattern of calcium-binding proteins, i.e. calbindin (CB) and parvalbumin (PV), as well as the colocalization pattern of all three proteins, including CR, in the ATN of guinea pigs ranging from the 40th embryonic day (E40) to the 80th postnatal day (P80). According to these patterns, CB appears exclusively in the perikarya of the anteromedial nucleus (AM) not before P20 and always colocalizes with CR. Moreover, CB and CR colocalize in fibers of thin bundles traversing the anteroventral nucleus (AV) since E50. The ATN also display CB-positive neuropil in all studied stages, especially a strong one in the ventral part of the AV. PV was not observed in the perikarya of the ATN in all the stages, but was abundantly present in the neuropil of the anterodorsal nucleus (AD). No colocalizations exist between PV and the rest of the studied proteins. In conclusion, our study reveals that the distribution of the studied proteins differs greatly. Nevertheless, the postnatal coexistence of CB and CR in the AM perikarya may indicate the cooperation of both of the proteins in some functions of the nucleus. Parvalbumin is limited mostly to the neuropil of the AD, suggesting different functions in comparison to CB and CR.