RAPID COMMUNICATION Three-Independent-Compartment Chamber to Study In Vitro Commissural Synapses

Khazipov, Roustem, Luc Desfreres, Ilgam Khalilov, and Yehezleum jelly (Vaseline) wall was used to separate two comkel Ben-Ari. Three-independent-compartment chamber to study in partments with spinal cord (Cazalets et al. 1996) and neonavitro commissural synapses. J. Neurophysiol. 81: 921–924, 1999. tal rat hippocampi (Khalilov et al. 1997) preparations. In We describe a novel chamber in which the two intact neonatal another study using spinal cord preparation, the compartrat hippocampi and the commissural fibers are placed in three ments were separated by plastic bars glued to the dorsal and independent compartments separated by latex membranes and perventral midlines of the cord (Kjaerulff and Kiehn 1997). fused selectively with different solutions. A set of control tests However, these approaches have certain disadvantages: the showed that the compartments are well isolated: 1) methylene Vaseline wall is unstable and melts fast at temperatures blue or eosin applied to one compartment did not diffuse to other higher than 307C, whereas the use of the glue might be toxic compartments when verified via the microscope, and spectrophotometry revealed that õ1/10.000th of the dye diffuses to other for the tissue. In addition, neither of these two approaches compartments; 2) tetrodotoxin (1 mM) applied to the commissural allows the application of drugs on the connecting fibers becompartment blocked the synaptic responses evoked contralaterally tween structures. without affecting those evoked on the ipsilateral side. This chamber Here we propose to isolate the compartments using latex enables a wide range of experiments that cannot be performed in membrane with an aperture adjusted to the size of the conconventional chambers, e.g., to study the maturation and plasticity nections between structures. The use of two membranes easof the commissural connections, bilateral synchronization of the ily allows the introduction of a thin intermediate compartrhythmic activities in the limbic system, commissural propagation ment to selectively perfuse the connections. We have also of the epileptiform activities, etc. ameliorated the system of perfusion by bringing the outlets from the compartments to an independent drawing-off cham-