The ontogenic expressions of multiple vesicular glutamate transporters during postnatal development of rat pineal gland

• Published in: Neuroscience 2008-03, Vol.152 (2), p.407-416
• Main Authors: Yoshida, S, Ina, A, Konno, J, Wu, T, Shutoh, F, Nogami, H, Hisano, S
• Format: Article
• Language: English
• Subjects: Age Factors; Animals; Animals, Newborn; Biological and medical sciences; day/night difference; dynamin; endophilin; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Developmental - physiology; glutamate; Neurology; Pineal Gland - growth & development; Pineal Gland - metabolism; pinealocyte; Rats; Rats, Sprague-Dawley; synaptic-like microvesicle; Synaptophysin - genetics; Synaptophysin - metabolism; Vertebrates: nervous system and sense organs; Vesicular Glutamate Transport Protein 1 - genetics; Vesicular Glutamate Transport Protein 1 - metabolism; Vesicular Glutamate Transport Protein 2 - genetics; Vesicular Glutamate Transport Protein 2 - metabolism
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/j.neuroscience.2007.12.029

Abstract The pineal gland expresses vesicular glutamate transporters 1 and 2 (VGLUT1 and VGLUT2), which are thought to transport glutamate into synaptic-like microvesicles in the pinealocytes. Recently, we reported that the rat pineal gland also expresses VGLUT1v which is a novel variant of VGLUT1 during the perinatal period. To explore the biological significance of these VGLUT expressions in pineal development, we studied the ontogeny of VGLUT in this gland by in situ hybridization, immunohistochemistry and quantitative reverse transcription–polymerase chain reaction (RT-PCR) using rats. Histological analysis revealed that intensities of VGLUT1 hybridization signal and immunostaining drastically increase by postnatal day (P) 7, whereas VGLUT2 expression exhibits high levels of mRNA and protein at birth and decreases gradually from P7 onward. Quantitative RT-PCR analysis supported these histological observations, showing that expressions of VGLUT1 and VGLUT2 exhibit opposite patterns to each other. Coinciding with VGLUT1-upregulation, RT-PCR data showed that expressions of dynamin 1 and endophilin 1, which are factors predictably involved in the endocytotic recovery of VGLUT1-associated vesicle, are also increased by P7. Quantitative RT-PCR analysis of VGLUT1v demonstrated that its mRNA expression is upregulated by P7, kept at the same level until P14, and apparently decreased at P21, suggesting its functional property required for a certain developmental event. Moreover, a comparison of mRNA expressions at daytime and nighttime revealed that neither VGLUT1 nor VGLUT1v shows any difference in both P7 and P21 glands, whereas VGLUT2 is significantly lower at daytime than at nighttime at P21 but not P7, the time point at which the melatonin rhythm is not yet generated. The present study shows that expressions of these VGLUT types are differentially regulated during postnatal pineal development, each presumably participating in physiologically distinct glutamatergic functions.