抄録
Mouse taste buds in fungiform papillae consist of ~50 cells. These taste bud cells (TBCs) expressed various neurotransmitter receptors, such as 5-HT and ATP receptors on their basolateral membranes. We investigated the functional expression and distribution of ATP receptors in single taste buds by monitoring [Ca2+]in with a Ca2+-sensitive dye, Fura-2 AM, in situ. Four taste buds out of eight contained ATP-sensitive TBCs. The application of 100 μM ATP to basolateral membranes increased [Ca2+]in in 4.5 ± 1.7 TBCs (mean ± SD, n = 4) an ATP-sensitive taste bud. Such ATP-sensitive TBCs preferably occurred in the central part of each taste bud. Under in-situ whole-cell clamp conditions, TBCs were depolarized and fired action potentials in response to the application of 100 μM ATP to their basolateral membranes. Although the application of 5-HT also increased [Ca2+]in, the ratio of 5-HT-sensitive taste buds to all taste buds examined was 0.35 (n = 62), the number of 5-HT-sensitive TBCs was 1.3 ± 0.8 (n = 22) a 5-HT-sensitive taste bud, and 5-HT-sensitive TBCs preferably occurred in the peripheral part of taste buds. So far, ATP and 5-HT receptors never coexist on the same TBCs, though they occurred in the same taste buds. These results showed that the expression of ATP and 5-HT receptors was differentially regulated. It appears that both ATP and 5-HT are used in a paracrine system in taste transduction mechanism and in forming cell-networks, though ATP- and 5-HT-releasing sites remain to be identified. [Jpn J Physiol 54 Suppl:S175 (2004)]
