Intracellular recording, electrical stimulation, receptive field mapping, HRP injection, and computer reconstruction techniques were used to study principalis cells in rat. They (n = 80) responded within 1.2 ± 0.2 ms of trigeminal ganglion shocks and 69% were antidromically activated by thalamic shocks; 69% were vibrissa-sensitive, of which 80% responded to only a single vibrissa. The remainder responded only to guard hairs, skin, teeth, or nociceptors. Stained thalamic-projecting cells with one vibrissa receptive fields had stereotyped morphologies. Small somata gave rise to dendrites which extended only a short distance from the soma, where they branched extensively. Each tree was polarized, spanning no more than a hemisphere around the soma; however, there was no consistent direction of polarity. Dendritic trees extended 68 ± 14, 95 ± 48, and 91 ± 29 μm in the transverse, sagittal and horizontal planes, respectively. Dendritic spines were rare, yet swellings were common. Axons never branched locally.
- Neuron morphometry
- Nucleus principalis