Biogenic monoamines in developing taste buds of mouse circumvallate papillae.

Abstract

After administration of monoamine precursors, developing taste buds of newborn and young mice were observed by means of EM and fluorescence histochemistry. Gustatory (type III) cells occurred in the primitive taste buds during stage 1 (0-1 day after birth). These cells had an immature type of afferent synaptic contacts with nerve terminals; no specific fluorescence was found in the taste buds after administration of 5-HTP [hydroxy tryptophan] or L-dopa. During stage 2 (2-7 days), mature types of afferent synapses, taste pores, type 1 cells and type II cells appeared in the taste buds; fluorescent cells appeared following treatment of 5-HTP or L-dopa. During stage 3 (14-21 days) the gustatory cells underwent ultrastructural changes following injection of 5-HTP, i.e., small dense-cored vesicles (30-60 nm) appeared scattered throughout the cytoplasm and intermingled with small clear vesicles accumulated at the presynaptic membranes of afferent synapses. The electron densities of large dense-cored vesicles (80-100 nm) were elevated as compared with those of untreated mice. The ability of gustatory cells to take up amine precursors started simultaneously with the formation of taste pores and mature afferent synapses between the gustatory cells and the sensory nerves.