Uptake and Release of d‐Aspartate, GABA, and Glycine in Guinea Pig Brainstem Auditory Nuclei

Abstract

This study attempts to determine if the medial (MSO) and lateral superior olive (LSO), medial nucleus of the trapezoid body (MNTB), ventral nucleus of the lateral lemniscus (VNLL), and central nucleus of the inferior colliculus (ICc) contain glutamatergic synaptic endings . Micropunch and microdissection procedures provided fresh samples of these auditory nuclei for the measurement of the high-affinity uptake and electrically evoked release of exogenous D-[3H]ASP. The study also determined if the LSO and MSO contain glycinergic synaptic endings by measuring uptake and release of ["C]-Gly in these nuclei, and whether the MNTB, VNLL, and ICc contain GABAergic endings by assessing the uptake and release of [' 4C]GABA in these structures . Several strategies optimized the evoked Ca Z+-dependent release of the labeled amino acids. These included the enhancement of high-affinity uptake during loading of the markers into the tissues, inhibition of uptake during the subsequent measurement of release, and use of an electrical stimulus current that evoked maximal Ca" -dependent release. Each of these nuclei manifested the high-affinity uptake and the evoked Ca 21 -dependent release of D-[3H]Asp, suggesting the presence of synaptic endings that may use Glu or Asp as a transmitter . Similar findings suggest the presence of glycinergic synaptic endings in the LSO and MSO, and of GABAergic synaptic endings in the MNTB, VNLL, and ICc . Key Words: Auditory nuclei-Superior olive-Ventral nucleus of lateral lemniscus-Inferior colliculus-D-Aspartate-GABA-Glycine-Uptake-Release.Abbreviations used: DPO, dorsal periolivary nucleus ; formolsaline, 10% formol/0 .9% saline ; IC, inferior colliculus ; We, central nucleus of the IC ; LSO, lateral superior olive ; MNTB, medial nucleus of the trapezoid body ; MSO, medial superior olive ; SOC, superior olivary complex ; VNLL, ventral nucleus of the lateral lemniscus ; VNTB, ventral nucleus of the trapezoid body .

Plasticity of the superior olivary complex

“…Neurons in the LSO receiving excitatory input are mostly located in the lateral limb; cells receiving inhibitory input mostly reside in the medial limb of the nucleus (Caspary and Faingold, 1989). The inhibitory input consists of both GABAergic (Helfert et al, 1992;Webster et al, 1990) and glycinergic synaptic terminals (Helfert et al, 1992;Suneja et al, 1995). Principal as well as other neurons of the LSO project to the IC (Elverland 1978;Glendenning andMasterton, 1980, 1983;Glendenning et al, 1981Glendenning et al, , 1985.…”

“…Neurons of MSO also receive descending input from IC (Elverland, 1977;Kiss and Majorossy, 1983), the lateral nucleus of the trapeziod body (LNTB; Cant, 1991;Kuwabara and Zook, 1992), and the MNTB (Kuwabara and Zook 1992). Inhibitory synaptic endings have been seen on neurons of the MSO, both GABAergic (Adams and Mugnaini, 1990;Webster et al, 1990) and glycinergic Sanes, 1993, 1994;Helfert et al, 1989;Suneja et al, 1995).…”

Bi-phasic intensity-dependent opioid-mediated neural amplitude changes in the chinchilla cochlea: Partial blockade by an N-Methyl-d-Aspartate (NMDA)-receptor antagonist

“…It is also generally accepted that glutamate is the excitatory neurotransmitter responsible for neural signaling in the mammalian cochlea and in brainstem auditory pathways (Ehrenberger and Felix, 1995;Puel, 1995;Suneja et al, 1995a;1995b;Usami et al, 2000). Ionotropic glutamate receptors are classified according to their pharmacology, molecular structure and biophysical properties.…”

Immunolocalization of vesicular glutamate transporters 1 and 2 in the rat inferior colliculus

“…The inferior colliculus (IC) receives multiple inputs from ascending and descending auditory pathways as well as from non-auditory inputs (Adams 1979, 1980, 1983, Aitkin et al, 1981Bajo and Moore, 2005;Cant & Benson, 2006;Jain & Shore, 2006;Loftus et al, 2004;Malmierca et al, 2005;Marsh et al, 2002;Merchan et al, 1994;Moore et al, 1998;Okayama et al, 2006;Oliver, 2000;Oliver et al, 1997;Osen, 1972;Saldana et al, 1996;Shofield, 2002;Shofield and Cant, 1996;Zhou, 2006, Tokunaga et al, 1984;Zhou and Shore, 2006) many of which are glutamatergic (Malmierca, 2003 for review;Alibardi, 1998;Feliciano and Potashner, 1995;Ross et al, 1995;Saint Marie, 1996, Suneja et al, 1995. The present study used co-immunolabeling to determine if VGLUT1 and VGLUT2 would differentiate unique and characteristic patterns of glutamatergic inputs onto neurons in the rat IC and to determine if there would be differences in the patterns in three sub-regions of the IC; the central nucleus (CIC), the lateral (external) cortex (LCIC) and the dorsal cortex (DCIC).…”