A POSSIBILITY OF EFFERENT INNERVATION OF THE GUSTATORY CELL IN THE RAT CIRCUMVALLATE TASTE BUD

A transmission-electron microscope study of the rat circumvallate tast e bud revealed that occasionally one and the same gustatory or Type II I cell received innervation associated with subsurface cisterns as the Type II cell did, in addition to the ordinary afferent synapse. The s ubsurface cistern, a flattened, smooth-surfaced saccular membrane syst em, hugged the plasma membrane of the gustatory cell along the boundar y against the nerve terminal. The nerve terminal attaching to the cell was occupied with mitochondria and synaptic type vesicles. As these s tructural features resemble those of efferent synapses in certain othe r sensory cells including the inner ear hair cells, the gustatory cell s dually innervated as demonstrated in the present study are presumabl y involved not only in the afferent but also in the efferent projectio n of nerves.