A NOVEL CARBON-FIBER BUNDLE MICROELECTRODE AND MODIFIED BRAIN SLICE CHAMBER FOR RECORDING LONG-TERM MULTIUNIT ACTIVITY FROM BRAIN-SLICES

The fabrication and characteristics of a novel multiunit recording ele ctrode and modified brain slice chamber suitable for long-term recordi ng from brain slices are described. The electrode consisted of an elec trolyte-filled glass micropipette with a 20-50 mu m thick wax-coated b undle of 5-mu m diameter carbon fibers extending 2.5 cm from the taper ed end and an AgCl-coated silver wire inserted into the open end and c onnected to a preamplifier. Both ends of the electrode were sealed wit h wax to prevent evaporation of the electrolyte. The brain slice was m aintained over this extended period in an interface-type brain slice c hamber modified to completely surround the slice with medium. Using th is electrode, regular 24-h oscillations of spontaneous multiunit activ ity were recorded for 3 days from a single location in a 500 mu m thic k rat suprachiasmatic nucleus brain slice. Preliminary data suggest th at this novel carbon fiber bundle electrode will be a favorable altern ative to traditional metal electrodes for long-term recording of multi unit activity from brain slices.