Organotypic suprachiasmatic nuclei cultures of adult voles reflect locomotor behavior: Differences in number of vasopressin cells

This study is the first to demonstrate organotypic culturing of adult supra chiasmatic nuclei (SCN). This approach was used to obtain organotypic SCN c ultures from adult vole brain with a previously determined state of behavio ral circadian rhythmicity. We examined vasopressin (AVP) immunoreactivity i n these organotypic slice cultures. AVP is one of the major neuropeptides p roduced by the SCN, the main mammalian circadian pacemaker. AVP immunoreact ivity in the SCN of adult common voles in vivo has been shown to correlate with the variability in expression of circadian wheel-running behavior. Her e, cultures prepared from circadian rhythmic and nonrhythmic voles were pro cessed immunocytochemically for AVP. Whereas in all cultures AVP could be o bserved, AVP immunoreactivity differed considerably between vole SCN cultur es. SCN cultures from rhythmic voles contained significantly lower numbers of AVP immunoreactive (AVPir) cells per surface area than cultures from non rhythmic voles. The correlation between timing of behavior and AVP immunore activity in vitro is similar to the correlation found earlier in vivo. Appa rently, such correlation depends on intrinsic AVP regulation mechanisms of SCN tissue, and not on neural or hormonal input from the environment, as pr esent in intact brain.