A morphological study for isolation of a single rat trigeminal motoneuron

We conducted a morphological study for isolation of a single neuron to investigate the electrophysiological properties of trigeminal motoneurons in a further study using the patch clamp technique. Transverse slices of rat brain stem containing the trigeminal motor nucleus (200-300 microns thick) were prepared and stained by the methylene blue staining method. The trigeminal motor nuclei, approximately 1,000 microns in diameter, were identified as densely stained regions in the slices. The somata of motoneurons were classified into two types by shape; ellipsoidal and spherical. The ellipsoidal somata were 50.3 +/- 12.3 microns (mean +/- S.D., n = 290) in long axis and 21.8 +/- 5.3 microns (n = 290) in short axis. The spherical somata were 35.0 +/- 6.9 microns (n = 290) in long axis and 29.3 +/- 5.7 microns (n = 290) in short axis. The neurons were all multipolar with 2-8 dendrites emanating from the soma.