The calcium-binding protein parvalbumin is selectively expressed in various subpopulations of neurons in the central and peripheral nervous system. The localization and percentage composition of parvalbumin-immunoreactive neurons were determined in the metasympathetic enteric ganglia of the small and large intestine in rats of different ages (1, 10, 20, 30, and 60 days and two years). Parvalbumin-immunoreactive neurons were present in the intermuscular plexus during ontogeny, from birth to old age, and the percentage of these cells in the intermuscular plexus in the small intestine increased from day 10 to day 20 of life and in that of the large intestine in the first 10 days of life. Parvalbumin was absent from the submucous plexus of the small and large intestine in neonatal rats, but w as present from day 10. The percentage of parvalbumin-immunoreactive neurons in the submucous plexus increased between day 10 and day 20 of life. On aging, the proportions of parvalbumin-immunoreactive neurons in the intermuscular and submucous plexuses did not change significantly. Thus, the proportion of parvalbumin-immunopositive neurons in the intramural intestinal ganglia increased in early postnatal ontogeny. This increase is probably associated with the buffer role of parvalbumin in relation to Ca2+ ions.
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