Primary culture of postnatal rat suprachiasmatic neurons in serum-free supplemented medium

Synthesis and Structure-Activity Relationships of Bioactive Compounds Using Sterols

Sterols are widely and abundantly distributed in nature. It is convenient to utilize them for the preparation of useful compounds such as pharmaceuticals with steroid and secosteroid skeletons. This paper describes the synthesis and structure-activity relationships of naturally occurring active forms of vitamin D analogues, sterols having neurite outgrowth activity, and liver X receptor agonist. The active form of vitamin D(4) showed similar biological activities but had higher affinity to the vitamin D-binding protein compared with the corresponding vitamins D(2) and D(3). This shows that the active form of vitamin D(4) is a good candidate for an agent to replace the active forms of vitamins D(2) and D(3). In the course of screening for low molecular-weight compounds that exhibit neurite outgrowth activity in the culture broth, we found that the natural product dictyosterol showed strong activity. From screening of the analogues, it was found that the double bond between C22 and C23 in the side chain of the sterol is essential for its activity. Ergost-22-ene-1alpha,3beta-diol was found to serve as a stronger liver X receptor agonist than 24(S), 25-epoxycholesterol, which regulates the expression of genes involved in lipid metabolism. Structure-function study showed that the 1alpha-hydroxyl group, the saturated steroid structure, and the double bond between C22 and C23 are needed to function as a liver X receptor agonist.

Primary cell culture of suprachiasmatic nucleus

In mammals, the suprachiasmatic nucleus (SCN) contains a biological clock that drives circadian rhythms in vivo and in vitro. Primary dissociated neuronal culture is a useful research tool, which allows cell-by-cell morphological and physiological study of the SCN. A long-term primary dissociated SCN neuron culture is the prerequisite to understanding how neural activity and morphology interact in the SCN. The essential details of recent effective SCN culture methods are reviewed, including preparation of cells, medium and substrate, maintenance of cultures, and characterization of cultured SCN neurons. This technique is growing in importance, especially with the advent of multi-electrode array (MEA) recording.

The suprachiasmatic nucleus in organotypic slice cultures of the common vole (Microtus arvalis): comparison of development with rat and hamster and the effect of age

The intrinsic properties of the suprachiasmatic nucleus (SCN), the site of the main circadian pacemaker in mammals, have recently been studied in vitro by means of organotypic slice culturing. So far, only neonatal rats and mice have been used for such developmental and functional analyses of the isolated pacemaker. Here, the authors present a comparative developmental study of the SCN of voles, rats, and hamsters in organotypic slice cultures. In contrast to strictly circadian organization of behavior in rats and hamsters, common voles (Microtus arvalis) are characterized by large variability in the strength of circadian organization of behavior. It is not known to what extent this variability is reflected in the intrinsic features of the SCN. Cultures were prepared from rat, hamster, and vole pups (6 to 9 days old) for the purpose of species comparison. In addition, the authors studied the relation between age and development in cultures from pup (7 to 10 days old), juvenile (15 to 16 days old), and young adult (1 to 2 months old) voles. In contrast to the situation in rat and hamster, the most striking feature in neonatal voles is the variability in shape of the final, fully developed culture and its poor resemblance with the in vivo SCN. The SCN of adult voles, however, could be cultured successfully while retaining its morphological organization seen in situ. Phase-contrast microscopy and immunocytochemical staining for vasopressin and glial fibrillary acidic protein revealed that cultures of pup and juvenile voles still have potential for neurogenesis and morphological reorganization. Young voles, therefore, can serve as a model to study the developmental establishment of a functional circadian pacemaker, while adult voles allow the study of intrinsic pacemaker properties in relation to previously recorded behavior of the donor and aging-related pacemaker dysfunction.

Cellular requirements of suprachiasmatic nucleus transplants for restoration of circadian rhythm

Fetal neurografts containing the suprachiasmatic nucleus (SCN) can restore the circadian locomotor and drinking rhythm of SCN-lesioned (SCNX) rat and hamster. This functional outcome finally proves that the endogenous biological clock autonomously resides in the SCN. Observations on the cellular requirements of the "new" SCN for restoration of the arrhythmic SCNX animals have led to some new insights and confirmed findings from other studies. A critical mass of SCN neurons appeared necessary for functional effects, whereas the temporal profile of reinstatement of rhythm correlated with the delayed maturation of the grafted SCN. Cytoarchitectonically, the grafted SCN does not seem to develop normally for all anatomical aspects. Complementary clusters of vasoactive intestinal polypeptide(VIP)- and vasopressin(VP)ergic neurons are formed, but somatostatin(SOM)ergic neurons do not always "join" this group, as is normally seen in situ. Nevertheless, these new SCNs can restore the ablated functions. As the period length of restored rhythms tends to vary, it might be that the grafted SCN underwent an altered or impaired maturation that resulted in a different setting of its clock mechanism. A prominent role of VIPergic neurons seems indicated by their presence in all functional grafts, but, although they may be required, these cells do not appear to be a sufficient condition for restoration of rhythm. Many grafts exhibit the presence of VIPergic cells without counteracting the arrhythmia, whereas VP- and SOMergic SCN neurons are usually present as well. Findings with VP-deficient Brattleboro rat grafts indicated that VP is not the primary obligatory signal of circadian activity. It is argued that perhaps the role of SOMergic neurons in the clock function of the (grafted) SCN has been insufficiently considered. However, one should keep in mind that the peptides of the various types of SCN neurons may function only as cofactors, mutually modulating molecular or bioelectrical cellular activities within the nucleus or the message of the main transmitter gamma-aminobutyric acid.