The dorsal cell, one class of primary sensory neuron in the lamprey spinal cord. II. A light- and electron...

Dorsal cells, are primary sensory neurons located in the lamprey spinal cord. They are of two types conveying touch (T) and pressure (P) and they have an ascending and/or a descending axon which joins the dorsal column. Dorsal cells have no initial axon segment. In the electron microscope synaptic boutons with spherical synaptic vesicles were found in contact with the cell membrane of T-cells while no boutons have been observed on P-cells. No other morphological differences between T- and P-cells could be detected ultrastructurally or in the light microscope. No output synapses have been observed from the dorsal cell bodies or the small processes extending from the cell body.