Biomedical subjects

S H Wu

Publications and source records attributed to S H Wu.

At least 55 records · Page 3Linked to original sources

PubMed2000

[Functional and structural study of the prokaryotic enhancer-like element VV16 from vaccinia virus genome].

An enhancer-like element VV16 from Vaccinia virus genome DNA was obtained by using the plasmid with CAT reporter gene. Sequence analysis showed the element of 112 bp is a part of the DNA-dependent RNA polymerase, polyA polymerase and DNA polymerase (RPO30 gene). It contains 4 AT-rich regions. Detection of beta-galactosidase activity showed that VV16 in the positive direction can increase the activity 9.0 times and VV16 in the negative direction can increase 4.1 times. The RNA dot blotting confirmed the enhancing activity of the element are on the transcription level. DNA deletion experiment indicated the sequences of 10 bp at the 5' end and 12 bp at the 3' end in the element are important to its function and the sequence from nt76 to nt82 is essential to its activity.

Enhancer Elements, Genetic↗

PubMed2000

[Separation and determination of tyramine by reversed-phase high performance liquid chromatography].

The method for separation and determination of tyramine by reversed-phase high performance liquid chromatography has been established. The effects of mobile phase on mechanism of separation based on the ion interaction are discussed. Using C8 alkyl bonded phase and 40% methanol-water solution containing Trisperchlorate as pH buffer (adjusted pH to 7.9) and ion interaction reagent and applying p-toluene sulfonamide as internal standard substance, the tyramine obtained from decarboxylation of p-tyrosine was determined. The RSD of determination was 0.66%(n = 11). The recoveries of sample were between 99.33% and 100.38%.

Alkylation↗

PubMed1999

Lipase-catalyzed acetylation of N-acetylneuraminic acid derivative.

A facile preparation of triacetylated derivative of 2-phenylthioglycoside of N-acetylneuraminic acid (4) was achieved by treatment with lipase PS in vinyl acetate. The major product 4 has a free hydroxyl group at C-7. Results of time-course HPLC analysis indicate that the reactivity of the hydroxyl groups under this condition is in the following order; C-9 > C-4 > C-8 > C-7.

Acetylation↗

PubMed1999

Controlled acid hydrolysis of colominic acid under microwave irradiation.

The hydrolysis of colominic acid under microwave irradiation was studied and compared with traditional heating methods. The microwave irradiation has several advantages over the heating method in the hydrolysis of colominic acid: (a) products with higher degrees of polymerization are obtained, (b) less lactone byproducts are observed, and (c) the hydrolytic rate is much faster. These advantages are probably due to the microwave effect. Oligosialic acids as the products of the acid hydrolysis of polysialic acid with conventional heating methods were fully lactonized, especially under the conditions of higher temperature and stronger acid.

Hydrolysis↗

PubMed1999

Purification, characterization and molecular cloning of trichoanguin, a novel type I ribosome-inactivating protein from the seeds of Trichosanthes anguina.

The seeds of the plant Trichosanthes anguina contain a type I ribosome-inactivating protein (RIP), designated trichoanguin, which was purified to apparent homogeneity by the combined use of ion-exchange chromatographies, i.e. first with DE-52 cellulose and then with CM-52 cellulose. The protein was found to be a glycoprotein with a molecular mass of 35 kDa and a pI of 9.1. It strongly inhibits the protein synthesis of rabbit reticulocyte lysate, with an IC50 of 0.08 nM, but only weakly that of HeLa cells, with an IC50 of 6 microM. Trichoanguin cleaves at the A4324 site of rat 28 S rRNA by its N-glycosidase activity. The cDNA of trichoanguin consists of 1039 nt and encodes an open reading frame coding for a polypeptide of 294 amino acid residues. The first 19 residues of this polypeptide encode a signal peptide sequence and the last 30 residues comprise an extension at its C-terminus. There are four potential glycosylation sites, located at Asn-51, Asn-65, Asn-201 and Asn-226. A comparison of the amino acid sequence of trichoanguin with those of RIPs such as trichosanthin, alpha-momorcharin, ricin A-chain and abrin A-chain reveals 55%, 48%, 36% and 34% identity respectively. Molecular homology modelling of trichoanguin indicates that its tertiary structure closely resembles those of trichosanthin and alpha-momorcharin. The large structural similarities might account for their common biological effects such as an abortifacient, an anti-tumour agent and anti-HIV-1 activities. Trichoanguin contains two cysteine residues, Cys-32 and Cys-155, with the former being likely to be located on the protein surface, which is directly amenable for conjugation with antibodies to form immunoconjugates. It is therefore conceivable that trichoanguin might be a better type I RIP than any other so far examined for the preparation of immunotoxins, with a great potential for application as an effective chemotherapeutic agent for the treatment of cancer.

Amino Acid Sequence↗

PubMed1999

Homology modeling of cephalopod lens S-crystallin: a natural mutant of sigma-class glutathione transferase with diminished endogenous activity.

The soluble S-crystallin constitutes the major lens protein in cephalopods. The primary amino acid sequence of S-crystallin shows an overall 41% identity with the digestive gland sigma-class glutathione transferase (GST) of cephalopod. However, the lens S-crystallin fails to bind to the S-hexylglutathione affinity column and shows very little GST activity in the nucleophilic aromatic substitution reaction between GSH and 1-chloro-2,4-dinitrobenzene. When compared with other classes of GST, the S-crystallin has an 11-amino acid residues insertion between the conserved alpha4 and alpha5 helices. Based on the crystal structure of squid sigma-class GST, a tertiary structure model for the octopus lens S-crystallin is constructed. The modeled S-crystallin structure has an overall topology similar to the squid sigma-class GST, albeit with longer alpha4 and alpha5 helical chains, corresponding to the long insertion. This insertion, however, makes the active center region of S-crystallin to be in a more closed conformation than the sigma-class GST. The active center region of S-crystallin is even more shielded and buried after dimerization, which may explain for the failure of S-crystallin to bind to the immobilized-glutathione in affinity chromatography. In the active site region, the electrostatic potential surface calculated from the modeled structure is quite different from that of squid GST. The positively charged environment, which contributes to stabilize the negatively charged Meisenheimer complex, is altered in S-crystallin probably because of mutation of Asn99 in GST to Asp101 in S-crystallin. Furthermore, the important Phe106 in authentic GST is changed to His108 in S-crystallin. Combining the topological differences as revealed by computer graphics and sequence variation at these structurally relevant residues provide strong structural evidences to account for the much decreased GST activity of S-crystallin as compared with the authentic GST of the digestive gland.

Algorithms↗

PubMed1999

Synaptic excitation in the dorsal nucleus of the lateral lemniscus.

The dorsal nucleus of the lateral lemniscus (DNLL) is a distinct auditory neuronal group located ventral to the inferior colliculus (IC). It receives excitatory and inhibitory afferent inputs from various structures of the auditory lower brainstem and sends GABAergic inhibitory efferents mainly to the contralateral DNLL and the bilateral IC. The synaptic excitation in DNLL neurons consists of two components, an early fast depolarization and a later long lasting one. Glutamate is the probable excitatory neurotransmitter for DNLL neurons. alpha-Amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA) receptors mediate the early part of the excitation while N-Methyl-D-aspartate (NMDA) receptors mediate the long lasting component. The long lasting NMDA receptor-mediated component in the DNLL may contribute to a prolonged inhibition in the IC. The DNLL is thought to be a structure for processing binaural information. Most DNLL neurons in rat and bat are sensitive to interaural intensity differences (IIDs). They are excited by stimulation of the contralateral ear and inhibited by stimulation of the ipsilateral ear, showing an excitatory/inhibitory (EI) binaural response pattern. The EI pattern can be attributed to synaptic inputs that originate from various structures in the lower auditory brainstem and impinge on the DNLL neurons. In cat some DNLL neurons are sensitive to IIDs and some are sensitive to interaural time differences. In addition, DNLL neurons exhibit different temporal response patterns to contralateral tonal stimulation and respond to amplitude modulated tones, implying that DNLL may contribute to processing temporally complex acoustic information. DNLL neurons shape binaural responses in the contralateral inferior colliculus and auditory cortex through their inhibitory brainstem projections and contribute to the accuracy with which animals localize sounds in space.

Animals↗

PubMed1999

The commissure of probst as a source of GABAergic inhibition.

Whole-cell patch-clamp recordings were made from neurons in the rat's dorsal nucleus of the lateral lemniscus (DNLL) in a brain slice preparation. Planes of section were chosen to preserve the integrity of fibers in the commissure of Probst (CP) and postsynaptic responses were evoked by electrical stimulation along its length. Results showed that the crossed projection to the DNLL through the CP is mainly, if not exclusively, inhibitory in the rat. Inhibitory postsynaptic responses (IPSPs) evoked by stimulation of the CP were blocked by the gamma-aminobutyric acid (GABA)(A) receptor antagonist bicuculline, but were unaffected by the glycine receptor antagonist strychnine, supporting the conclusion that the crossed inhibitory projection to DNLL from the contralateral DNLL is GABAergic. Stimulation of the CP close to the DNLL frequently evoked excitatory postsynaptic responses as well as IPSPs, but stimulation near the midline evoked IPSPs only. Thus, the excitatory responses probably originated from a pathway other than the projection to the DNLL from the contralateral DNLL through the CP.

Animals↗

PubMed1999

Physiological properties of neurons in the ventral nucleus of the lateral lemniscus of the rat: intrinsic membrane properties and synaptic responses.

The physiological properties including current-voltage relationships, firing patterns, and synaptic responses of the neurons in the ventral nucleus of the lateral lemniscus (VNLL) were studied in brain slices taken through the young rat's (17-37 days old) auditory brain stem. Intracellular recordings were made from VNLL neurons, and synaptic potentials were elicited by electrical stimulation of the lateral lemniscus ventral to the VNLL. Current-voltage relations and firing patterns were tested by recording the electrical potentials produced by intracellular injection of positive and negative currents. There were two types of VNLL neurons (type I and II) that exhibited different current-voltage relationships. In response to negative current, both type I and II neurons produced a graded hyperpolarization. Type I neurons responded to positive current with a graded depolarization and multiple action potentials the number of which was related to the strength of the current injected. The current-voltage relations of type I neurons were nearly linear. Type II neurons responded to positive current with a limited depolarization and only one or a few action potentials. The current-voltage relations of type II neurons were nonlinear near the resting potential. The membrane properties of the type II VNLL neurons may play an important role for processing information about time of onset of a sound. Type I neurons showed three different firing patterns, i.e., regular, onset-pause and adaptation, in response to small positive current. The onset-pause and adaptation patterns could become sustained when a large current was injected. The regular, onset-pause, and adaptation patterns in type I neurons and the onset pattern in type II neurons resemble "chopper," "pauser, " "primary-like," and "on" responses, respectively, as defined in in vivo VNLL studies. The results suggest that different responses to acoustic stimulation could be attributed to intrinsic membrane properties of VNLL neurons. Many VNLL neurons responded to stimulation of the lateral lemniscus with excitatory or inhibitory responses or both. Excitatory and inhibitory responses showed interaction, and the output of the synaptic integration depended on the relative strength of excitatory and inhibitory responses. Neurons with an onset-pause firing pattern were more likely to receive mixed excitatory and inhibitory inputs from the lower auditory brain stem.

Animals↗

PubMed1998

Identification of free deaminated sialic acid (2-keto-3-deoxy-D-glycero-D-galacto-nononic acid) in human red blood cells and its elevated expression in fetal cord red blood cells and ovarian cancer cells.

Chemical studies have shown the occurrence of the deaminated sialic acid 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) in paired samples of blood obtained from mothers and newborns of healthy human individuals. Most of the KDN was found in red blood cells, although low levels were detected in mononuclear cells. No N-glycolylneuraminic acid was detected. Unexpectedly, nearly all of the KDN in fetal cord and matched maternal red blood cells was present as the free sugar and comparatively little occurred conjugated or as cytidine 5'-KDN phosphate. The amount of free KDN in fetal newborn red blood cells was 2.4-fold higher than in red blood cells from the mothers or from healthy nonpregnant women. Free KDN was also identified in normal human ovaries, in ovarian tumors, and in ascites cells obtained from ovarian cancer patients. Importantly, as in fetal cord red blood cells, a distinguishing feature of KDN expression in ovarian tumor cells was an elevated level of free KDN compared with normal controls. A positive correlation was found between an increase in the ratio of free KDN/N-acetylneuraminic acid in ovarian adenocarcinomas and the stage of malignancy. This was particularly evident in tumor cells isolated from the ascites fluid. The central importance of these new findings is 2-fold. First, they show that free KDN is a minor but ubiquitous sialic acid in human red blood cells and that its elevated expression in red blood cells from fetal cord blood compared with maternal red blood cells may be developmentally related to blood cell formation during embryogenesis. Second, the enhanced expression of KDN in ovarian cancer cells suggests that this sialic acid, like the alpha2,8-linked polysialic acid glycotope, may be an oncofetal antigen in these tumors and thus could be an "early warning" signal for onset of disease and/or a marker for detection of recurrence of disease. These new findings highlight the importance of elucidating the role that KDN and KDN-containing glycoconjugates may play in normal development and malignancy.

Adenocarcinoma↗

PubMed1998

Characterization of phospholipase A2 (PLA2) from Taiwan Cobra: isoenzymes and their site-directed mutants.

Extracellular and secretory phospholipase A2 (PLA2), a class of phospholipid digesting enzyme, is widely distributed in animal venoms of reptiles and insects. Two cDNAs encoding PLA2 isoenzymes from Taiwan Cobra (Naja naja atra) were cloned into pQE-30 plasmid vector and expressed in Escherichia coli. The recombinant products were subjected to refolding using sulfonation under reduction/oxidation conditions with glutathione and enterokinase removal of His-tag, resulting in the active recombinant PLA2 with the same molecular masses of native enzymes as determined by mass spectrometry. The recombinant PLA2 was also shown by circular dichroism to possess a secondary structure similar to native PLA2. The enzymatic activity of the major isoenzyme (PLA2-1) is higher than the other minor isoenzyme (PLA2-2), which shows two amino acid difference from PLA2-1. Site-directed mutagenesis was used to probe the structure/function relationship of two highly conserved residues among all reported PLA2, i.e., His-47 and Asp-93. Replacement of His-47 residue by either Ala or Arg resulted in the complete loss of activity. Similarly, the mutant Asp-93 --> Asn (D93N) also retained little activity. These results suggest that both His-47 and Asp-93 are essential for the catalytic activity of PLA2. Computer graphic study, based on homology modelling, highlights the differences between native PLA2 isoenzymes and their site-directed mutants, which may account for the differences in the observed biological activity.

Base Sequence↗

PubMed1998

Characterization of three endogenous peptide inhibitors for multiple metalloproteinases with fibrinogenolytic activity from the venom of Taiwan habu (Trimeresurus mucrosquamatus).

Three small peptide components were isolated and purified from the venom of Taiwan habu (Trimeresurus mucrosquamatus), which show specific activity to inhibit the strong proteolytic activity of multiple metalloproteinases present in the crude venom. Using multiple chromatographies coupled with successive ultrafiltrations, three inhibitors, i.e. pyroglutamate-lysine-tryptophan (pyroGlu-Lys-Trp), pyroglutamate-asparagine-tryptophan (pyroGlu-Asn-Trp) and pyroglutamate-glutamine-tryptophan (pyroGlu-Gln-Trp) were obtained in good yields and high homogeneity. The yields of these peptide fractions were estimated to be about 0.65 mg, 0.55 mg and 0.42 mg from 250 mg total lyophilized crude venom, which corresponded to the approximate concentrations of 8.4 mM, 7.3 mM and 5.4 mM respectively in venom secretion. Detailed and unambiguous structural determination was established by amino acid analyses, mass spectrometry and microsequencing of purified peptides. Further functional characterization of these three tripeptides showed that they could weakly inhibit three metalloproteinases previously isolated from the same venom. The inhibitory activities were similar among these tripeptides and their IC50 (concentration for 50% inhibition) were estimated in a range of 0.20-0.95 mM, which is much more effective than citrate, another venom protease inhibitor of low molecular-weight component. Since these tripeptides are the endogenous peptide inhibitors present in the lumen of venom glands, it is conceivable that they may act as a self-defensive mechanism against the auto-digestive deleterious effect of the strong metalloproteinases in vivo, particularly several zinc-dependent metalloproteinases present in crotalid and viperid venoms.

Amino Acid Sequence↗

PubMed1998

Chemical mechanism of the endogenous argininosuccinate lyase activity of duck lens delta2-crystallin.

The endogenous argininosuccinate lyase activity of duck delta2-crystallin was specifically inactivated by the histidine-specific reagent, diethyl pyrocarbonate. The protein was protected by l-citrulline or l-arginine from the diethyl pyrocarbonate inactivation. To characterize further the chemical mechanism of the delta2-crystallin-catalysed reaction, deuterium-labelled argininosuccinate was enzymically synthesized from fumarate and l-arginine with delta2-crystallin in 2H2O. The argininosuccinate synthesized contained about 19% of the anhydride form; however, the deuterium was clearly demonstrated to be incorporated enantioselectively. Only the pro-HR atom at C-9 of the succinate moiety was labelled in the [2H]argininosuccinate-9-d synthesized, which indicates an anti-elimination mechanism for the endogenous argininosuccinate lyase activity of delta2-crystallin. The enzymic activity of duck lens delta2-crystallin in the pH range 5.5-8.5 was investigated using both protium- and deuterium-labelled argininosuccinate as the substrate. From the logkcat versus pH plot, two molecular pKa values of 6.18+/-0.02 and 8.75+/-0.03 were detected in the delta2-crystallin-argininosuccinate binary complex. The former must be dehydronated and the latter hydronated to achieve an optimum reaction rate. The logkcat/Km versus pH plot suggested two molecular pKa values of 5.96+/-0.09 and 8.29+/-0.10 for the free delta2-crystallin to be involved in the substrate binding. Small kinetic isotope effects of 1.17+/-0.02 and 1.05+/-0.09 were found for kcat and kcat/Km respectively. Combining results from labelling and kinetic analysis indicates that the endogenous argininosuccinate lyase activity of duck delta2-crystallin is compatible with a stepwise E1cB mechanism, the rate-limiting step probably at the C-N bond-cleavage step.

Animals↗

PubMed1998

High-performance capillary electrophoretic characterization of different types of oligo- and polysialic acid chains.

We have carried out comparative structural analysis of novel oligo- and polysialic acid chains from diverse sources. Controlled acid hydrolysates of (a) colominic acid, alpha2-->8-linked homopolymer of N-acetylneuraminic acid (Neu5Ac), (b) alpha2-->8-linked oligo/polyNeu5Gc chains present in rainbow trout egg polysialoglycoprotein, and (c) alpha2-->8-linked oligomers of deaminoneuraminic acid (KDN) residues of KDN-rich glycoprotein derived from rainbow trout vitelline envelope were analyzed by high-performance capillary electrophoresis (HPCE). The results showed that three different types of alpha2-->8-linked oligosialic acids having same degree of polymerization can be separated by HPCE. A partial hydrolysate of colominic acid with mild acid was shown by CE to form intramolecular esters during the controlled hydrolysis and the subsequent workup procedure. In contrast, lactonization of (-->5-Oglycolyl-Neu5Gcalpha2-->)n, alpha2-->5-Oglycolyl-linked homopolymer of N-glycolylneuraminic acid (Neu5Gc) present in the egg jelly coat of sea urchin, did not take place as readily as in (-->8Neu5Acalpha2-->)n.

Animals↗

PubMed1998

Physiological role of the association complexes of alpha-crystallin and its substrates on the chaperone activity.

Previous reports on the chaperone activity of alpha-crystallin to prevent protein denaturation and thermal aggregation have suggested that partially denatured proteins can bind alpha-crystallin in its central region. Likewise, beta- and gamma-crystallin can also be localized to the central cavity of alpha-crystallin particle in vivo, which provides indirect evidence that alpha-crystallin can function as a chaperone in the intact lens. In this study, we have further demonstrated that the binding of the substrate proteins to alpha-crystallin by short-term preincubation may mimic the in vivo conditions of crystallin association. Preheating of alpha-crystallin with its substrate proteins at 60 degrees C for 20 min resulted in the formation of stable complexes between alpha-crystallin and its substrates (8.0% of insulin or 5.3% of gamma-crystallin was involved in complex formation). Under such conditions, the chaperone activity of alpha-crystallin to inhibit dithiothreitol-, ultraviolet-, or oxidation-induced protein aggregation can be greatly enhanced. Since UV-irradiation and oxidative stress are common insults to eye lenses under normal physiological conditions, the presence of alpha/gamma and alpha/beta complex in vivo may play an important role to maintain the lens in a transparent state.

Animals↗

PubMed1998

Characterization, cloning, and expression of porcine alpha B crystallin.

alpha-Crystallin is a major lens protein present in the lenses of all vertebrate species. Recent studies have revealed that bovine alpha-crystallins possess genuine chaperone activity similar to small heat-shock proteins. In order to compare this chaperone-like structural protein from the eye lenses of different mammalian species, we have cloned and expressed one of the main alpha-crystallin subunits, i.e., alpha B crystallin, from the porcine lenses in order to facilitate the structure-function evaluation and comparison of this chaperonin protein. cDNA encoding alpha B subunit chain was obtained using a new "Marathon cDNA amplification" protocol of Polymerase Chain Reaction (PCR). PCR-amplified product corresponding to alpha B subunit was then ligated into pGEM-T plasmid and prepared for nucleotide sequencing by the dideoxy-nucleotide chain-termination method. Sequencing several positive clones containing DNA inserts coding for alpha B-crystallin subunit constructed only one complete full-length reading frame of 525 base pairs similar to human and bovine alpha B subunits, covering a deduced protein sequence of 175 amino acids including the universal translation-initiating methionine. The porcine alpha B crystallin shows only 3 and 7 residues difference to bovine and human alpha B crystallins respectively, revealing the close relatedness among mammalian eye lens proteins. The sequence differences between porcine and sub-mammalian species such as chicken and bullfrog are much greater, especially at the N- and C-terminal regions of these alpha B crystallins. Expression of alpha B subunit chain in E. coli vector generated a polypeptide which can cross-react with the antiserum against the native and purified alpha B subunit from the native porcine lenses albeit with a much lower activity.

Amino Acid Sequence↗

PubMed1998

GABAergic projections from the lateral lemniscus to the inferior colliculus of the rat.

The objective of the present study was to provide direct evidence regarding GABAergic projections from the nuclei of the lateral lemniscus to the central nucleus of the inferior colliculus (ICC), and from the ICC to the opposite ICC. Projections of GABAergic neurons in the rat were investigated by a combination of fluorogold (FG) retrograde tracing and GABA immunocytochemistry. FG was first injected into a frequency-defined region (11-13 kHz) in the center of the ICC, and 1-2 weeks was allowed for retrograde transport. Vibratome sections were then cut through the brainstem and stained with GABA antibody. Double-labeling was taken as evidence of GABAergic neurons projecting to the ICC. The results from FG retrograde labeling alone showed that neurons in the dorsal nucleus of the lateral lemniscus (DNLL) bilaterally, in the intermediate and ventral nucleus of the lateral lemniscus (INLL and VNLL) ipsilaterally, and in the ICC contralaterally project to the ICC. GABA immunostaining alone showed substantial numbers of GABA positive neurons in the nuclei of the lateral lemniscus and the inferior colliculus. FG and GABA double-labeled neurons were present in all nuclei of the lateral lemniscus that project to the ICC. The greatest concentration of double-labeled neurons was found bilaterally in the DNLL, suggesting a prominent GABAergic projection from the DNLL to the ICC. The presence of many double-labeled neurons in the ipsilateral INLL and VNLL suggests that there are also GABAergic inputs from the INLL and VNLL to the ICC. No double-labeled neurons were found in the contralateral ICC, which suggests the possibility of a prominent non-GABAergic projection.

Animals↗

PubMed1998

Glutamate receptors underlying excitatory synaptic transmission in the rat's lateral superior olive studied in vitro.

Glutamate receptors underlying synaptic excitation in the rat's lateral superior olive were studied by whole-cell patch clamp recordings in a brain slice preparation. Recordings from two morphological types of cells, bipolar and multipolar, identified by intracellular labeling with biocytin, showed that there were no obvious differences in responses mediated or modulated by ionotropic and metabotropic receptors between these two types of neurons. The excitatory postsynaptic potentials (EPSPs) elicited by ipsilateral stimulation of the trapezoid body consisted of two components. An earlier component, which had faster rise time constant and decay time constant, was mediated by non-NMDA receptors. A later component, which had slower rise time and decay time constants, was mediated by NMDA receptors. Suprathreshold responses (action potentials), which arose from the early component, were always abolished by the non-NMDA antagonist, CNQX, but not by the NMDA antagonist, APV. These results suggest that both non-NMDA and NMDA receptors are present in LSO neurons, and that fast excitatory transmission in LSO is primarily mediated by non-NMDA receptors. The metabotropic glutamate receptor agonists, t-ACPD and L-AP4, reduced the size of EPSPs evoked by stimulation of the ipsilateral trapezoid body in LSO neurons; the reductive action of t-ACPD was reversed by the antagonist, MCPG, indicating that metabotropic glutamate receptors, probably group II and III subtypes, can modulate excitatory synaptic transmission in LSO.

6-Cyano-7-nitroquinoxaline-2,3-dione↗