PT  - JOURNAL ARTICLE
AU  - Yijen A. Huang
AU  - Yutaka Maruyama
AU  - Stephen D. Roper
TI  - Norepinephrine Is Coreleased with Serotonin in Mouse Taste Buds
AID  - 10.1523/JNEUROSCI.4187-08.2008
DP  - 2008 Dec 03
TA  - The Journal of Neuroscience
PG  - 13088--13093
VI  - 28
IP  - 49
4099  - http://www.jneurosci.org/content/28/49/13088.short
4100  - http://www.jneurosci.org/content/28/49/13088.full
SO  - J. Neurosci.2008 Dec 03; 28
AB  - ATP and serotonin (5-HT) are neurotransmitters secreted from taste bud receptor (type II) and presynaptic (type III) cells, respectively. Norepinephrine (NE) has also been proposed to be a neurotransmitter or paracrine hormone in taste buds. Yet, to date, the specific stimulus for NE release in taste buds is not well understood, and the identity of the taste cells that secrete NE is not known. Chinese hamster ovary cells were transfected with α1A adrenoceptors and loaded with fura-2 (“biosensors”) to detect NE secreted from isolated mouse taste buds and taste cells. Biosensors responded to low concentrations of NE (≥10 nm) with a reliable fura-2 signal. NE biosensors did not respond to stimulation with KCl or taste compounds. However, we recorded robust responses from NE biosensors when they were positioned against mouse circumvallate taste buds and the taste buds were stimulated with KCl (50 mm) or a mixture of taste compounds (cycloheximide, 10 μm; saccharin, 2 mm; denatonium, 1 mm; SC45647, 100 μm). NE biosensor responses evoked by stimulating taste buds were reversibly blocked by prazosin, an α1A receptor antagonist. Together, these findings indicate that taste bud cells secrete NE when they are stimulated. We isolated individual taste bud cells to identify the origin of NE release. NE was secreted only from presynaptic (type III) taste cells and not receptor (type II) cells. Stimulus-evoked NE release depended on Ca2+ in the bathing medium. Using dual biosensors (sensitive to 5-HT and NE), we found all presynaptic cells secrete 5-HT and 33% corelease NE with 5-HT.