Developmental maturation of ionotropic glutamate receptor subunits in rat vestibular nuclear neurons responsive to vertical linear acceleration

Abstract

We investigated the maturation profile of subunits of ionotropic glutamate receptors in vestibular nuclear neurons that were activated by sinusoidal linear acceleration along the vertical plane. The otolithic origin of Fos expression in these neurons was confirmed as a marker of functional activation when labyrinthectomized and/or stationary control rats contrasted by showing sporadically scattered Fos-labeled neurons in the vestibular nuclei. By double immunohistochemistry for Fos and one of the receptor subunits, otolith-related neurons that expressed either alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionate or N-methyl-d-aspartate subunits were first identified in the medial vestibular nucleus, spinal vestibular nucleus and Group x by postnatal day (P)7, and in the lateral vestibular nucleus and Group y by P9. No double-labeled neurons were found in the superior vestibular nucleus. Within each vestibular subnucleus, these double-labeled neurons constituted approximately 90% of the total Fos-labeled neurons. The percentage of Fos-labeled neurons expressing the GluR1 or NR2A subunit showed developmental invariance in all subnuclei. For Fos-labeled neurons expressing the NR1 subunit, similar invariance was observed except that, in Group y, these neurons decreased from P14 onwards. For Fos-labeled neurons expressing the GluR2, GluR2/3, GluR4 or NR2B subunit, a significant decrease was found by the adult stage. In particular, those expressing the GluR4 subunit showed a two- to threefold decrease in the medial vestibular nucleus, spinal vestibular nucleus and Group y. Also, those expressing the NR2B subunit showed a twofold decrease in Group y. Taken together, the postsynaptic expression of ionotropic glutamate receptor subunits in different vestibular subnuclei suggests that glutamatergic transmission within subregions plays differential developmental roles in the coding of gravity-related vertical spatial information.

Maturation of canal‐related brainstem neurons in the detection of horizontal angular acceleration in rats

“…The neuronal expression of c-fos allows us to map the distribution of the second-order and higherorder neurons within the central circuitry of the horizontal canal system. Input of canal origin leading to Fos expression within the vestibular nucleus, PrH and IO was confirmed by the basal level of Fos signal in labyrinthectomized rats with or without rotation and in normal stationary rats (Chen et al, 2003;Lai et al, 2004Lai et al, , 2006Lai et al, , 2008Tse et al, 2008).…”

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“…In general, the greatest c-Fos expression in response to vestibular stimuli is reported in MVN, SpVN, and SVN, as well as several related cell groups such as nucleus prepositus hypoglossi, the x-group, and the y-group. For example, sinusoidal linear acceleration in the horizontal (Zhang et al, 2005) and vertical (Lai et al, 2006, 2008) planes activates c-Fos in some neurons within MVN and SpVN, as well as ventral LVN, y-group, and x-group, but not SVN (Lai et al, 2006, 2008). In contrast, Fos-positive cells are observed in SVN as well as MVN and SpVN following OVAR in rodents (Chen et al, 2003; Lai et al, 2004; Tse et al, 2008) and other species (Gustave Dit Duflo et al, 1999; Baizer et al, 2010), whereas Ferris wheel stimulation results in more widespread c-Fos staining in the VNC (Cai et al, 2007).…”

“…These studies have sought to identify the locations and distributions of neurons activated by semicircular canal, otolith organ, or combined canal/otolith-related stimulation achieved through a variety of experimental paradigms including horizontal and vertical linear acceleration, Ferris wheel rotation, off-vertical-axis rotation (OVAR), centrifugation, spaceflight, and steps of galvanic vestibular stimulation (GVS; Kaufman et al, 1992b, 1993; Kaufman and Perachio, 1994; Marshburn et al, 1997; Gustave Dit Duflo et al, 2000; Saxon et al, 2001; Pompeiano et al, 2002; Chen et al, 2003; Fuller et al, 2004; Lai et al, 2004, 2006, 2008; Kaufman, 2005; Zhang et al, 2005; Cai et al, 2007, 2010; Tse et al, 2008; Abe et al, 2009; Baizer et al, 2010). In addition, a number of studies have used c-Fos to identify central vestibular neurons that are activated in response to unilateral or bilateral destruction or inactivation of receptor hair cells, individual end organs, the entire labyrinth or the vestibular nerves (Kaufman et al, 1992a, 1993, 1999; Kitahara et al, 1995, 1997; Cirelli et al, 1996; Darlington et al, 1996; Kim et al, 1997, 2002; Gustave Dit Duflo et al, 1999; Shinder et al, 2005a,b, 2006), since these cells and tissues may play key roles in the process of vestibular compensation.…”

Maturation of glutamatergic transmission in the vestibulo-olivary pathway impacts on the registration of head rotational signals in the brainstem of rats

“…The vestibular origin of Fos expression in these circuitries was confirmed using both labyrinthectomized rats with or without rotation and normal stationary rats (cf. Chen et al 2003;Lai et al 2008Lai et al , 2010Tse et al 2008). In normal experimental rats, Fos expression was only taken as an indicator of vestibular input when the average number of Fos-ir cells/section of each subnucleus was C4.…”