Journal of Neuroscience, Vol 8, 73-78, Copyright © 1988 by Society for Neuroscience
Morphology of chorda tympani fiber receptive fields and proposed neural rearrangements during development
CM Mistretta, S Gurkan and RM Bradley
Department of Oral Biology, School of Dentistry, University of Michigan, Ann Arbor 48109.
The average number of fungiform papillae in receptive fields of single
chorda tympani nerve fibers decreases during development in sheep, and a
greater proportion of small receptive fields that are highly responsive to
NaCl, compared with NH4Cl, is acquired. To learn whether there also are
developmental differences in the number of taste buds within the papillae
in mapped receptive fields, we studied the morphology of receptive fields
and fungiform papillae, and also counted fibers in the chorda tympani
nerve, in fetal, perinatal, and postnatal sheep. Whether defined as the
number of fungiform papillae or as the number of taste buds within
papillae, receptive fields of chorda fibers decrease developmentally.
Initially, however, there is an increase, and subsequently a decrease, in
the number of taste buds per field. The differences in field size cannot be
attributed to developmental alterations in numbers of fungiform papillae
because the total number of papillae on the tongue remains constant. The
average number of taste buds per papilla, however, also increases and then
decreases, and the increase in perinatal animals is accompanied by the
appearance of large, multipored taste buds. Because there is a significant
relation between fungiform papilla size and number of taste buds in the
papilla, papilla size could be one regulating factor for taste bud number.
Furthermore, the number of chorda tympani nerve fibers apparently increases
up to perinatal stages and then decreases postnatally, providing another
potential regulating factor for the number of taste buds.(ABSTRACT
TRUNCATED AT 250 WORDS)