Intracellular recordings from rat thalamic VL neurons: a study combined with intracellular staining

Intracellular recordings from thalamic neurons receiving cerebellar inputs were performed under urethane anesthesia in the rat. A total of 64 neurons were recorded intracellularly with micropipettes filled with 4% biocytin solution (dissolved in 0.5 M K-acetate), and cerebellar-induced EPSPs (CN-EPSPs), the membrane resistance and firing properties were analyzed with intracellular current injections. The mean latency of CN-EPSPs was 1.9 +/- 0.8 ms and the mean input resistance measured in 10 neurons was 17.6 +/- 5.0 M omega. Thirty-two out of 35 stained neurons were analysed morphologically; 28 of these neurons were located in the VL, and 26 received CN-EPSPs. Their somata were round or polygonal in shape and the mean size was 22.5 x 15.2 microns. They had radially extending spinous dendrites, and the mean radii of the dendritic fields were 214.7 microns in the frontal and 171.4 microns in the sagittal planes. These morphological features were similar to those observed in the sensory relay nucleus of the thalamus.