Immunolocalization of vesicular glutamate transporter 2 and exocytosis‐related proteins in afferent nerve endings innervating taste buds in the rat incisive papilla

Abstract

AbstractThe present study aimed to investigate the immunolocalization of vesicular glutamate transporter (VGLUT) 1 and 2, and proteins associated with exocytosis, i.e., core components of the soluble N‐ethylmaleimide‐sensitive factor attachment protein receptor complex (synaptosomal‐associated protein of 25 kDa, syntaxin 1, and vesicle‐associated membrane protein 2) and synaptotagmin‐1 (Syt1), in incisive papillary taste buds of rats using double‐indirect immunofluorescence. No VGLUT1 immunoreactivity was observed, whereas VGLUT2‐immunoreactive punctate products were closely associated with guanine nucleotide‐binding protein G(t) subunit α3‐immmunoreactive cells in taste buds. VGLUT2 was immunolocalized in P2X3 purinoceptor‐expressing afferent nerve endings. Synaptosomal‐associated protein of 25 kDa, syntaxin 1, and vesicle‐associated membrane protein 2 were immunolocalized in nerve endings containing VGLUT2‐immunoreactive products as well as a few cells in taste buds. VGLUT2 was co‐immunolocalized in some intragemmal nerve endings immunoreactive for Syt1, a calcium sensor implicated in vesicle membrane fusion. The present results suggest that afferent nerve endings innervating incisive taste buds release glutamate by exocytosis to modulate taste cell function.