SEARCH · PubMed Health

Results for “Microinjection”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 397 records · Page 22Linked to original sources

PubMed2004

Effect of DNA loop anchorage regions (LARs) and microinjection timing on expression of beta-galactosidase gene injected into one-cell rabbit embryos.

The conditions favoring expression of a reporter gene microinjected into a male pronucleus of naturally ovulated and fertilized rabbit eggs have been studied. Injection of the reporter gene during S phase of the cell-cycle allows the highest level of expression of the gene. Incorporation of DNA loop anchorage regions (LARs) into constructs upstream and/or downstream of the reporter gene significantly increased the efficiency of expression. In all cases the expression of the microinjected gene started after a period of transcriptional quiescence, i.e., together with the expression of the host genome. Correct targeting of microinjected constructs within the nuclei via interaction of LAR elements with receptor sites on the nucleoskeleton may facilitate expression of injected DNA constructs as well as their integration into host cell DNA.

Animals↗

PubMed1989

Microinjection of inositol 1,2-(cyclic)-4,5-trisphosphate, inositol 1,3,4,5-tetrakisphosphate, and inositol 1,4,5-trisphosphate into intact Xenopus oocytes can induce membrane currents independent of extracellular calcium.

Inositol phosphate action in an intact cell has been investigated by intracellular microinjection of eight inositol phosphate derivatives into Xenopus laevis oocytes. These cells have calcium-regulated chloride channels but do not have a calcium-induced calcium release system. Microinjection of inositol 1,3,4,5-tetrakisphosphate (IP4), inositol 1,2-(cyclic)-4,5-trisphosphate (cIP3), inositol 1,4,5-trisphosphate (IP3), or inositol 4,5-bisphosphate [(4,5)IP2], open chloride channels to induce a membrane depolarization. However, inositol 1-phosphate (IP1), inositol 1,3,4,5,6-pentakisphosphate (IP5), inositol 1,4-bisphosphate, or inositol 3,4-bisphosphate are unable to induce this depolarization. The depolarization is mimicked by calcium microinjection, inhibited by EGTA coinjection, and is insensitive to removal of extracellular calcium. By means of the depolarization response, the efficacy of various inositol phosphate derivatives are compared. IP3 and cIP3 induce similar half-maximal, biphasic depolarization responses at an intracellular concentration of approximately 90 nM, whereas IP4 induces a mono- or biphasic depolarization at approximately 3400 nM. At concentrations similar to that required for IP3 and cIP3, (4,5)IP2 induces a long-term (greater than 40 min) depolarization. The efficacy (cIP3 = IP3 = (4,5)IP2 much greater than IP4) and action of the various inositol phosphates in an intact cell and their inability to induce meiotic cell division are discussed.

Animals↗

PubMed1990

Cytological effects of the microinjection of antibody to ras p21 in early cleavage Xenopus embryos.

The presence of two ras-related proteins (22 and 23 kDa) was demonstrated in Xenopus embryonic extracts by selective immunoprecipitation using anti-ras monoclonal antibodies 142-24E05 and Y13-259. We further describe the cytological effects of the microinjection of anti-ras monoclonal antibody Y13-259 into early cleavage blastomeres of Xenopus embryos. Injection of the antibody into a blastomere at the two-, four-, or eight-cell stage caused cleavage arrest in the descendants of the injected blastomere. Light microscopy (LM) of cleavage-arrested cells revealed extensive deformation of the cells as well as heterogeneity of distribution of yolk platelets and pigment granules. LM analysis of serial sections of cleavage-arrested cells revealed the presence of multiple nuclei. Although the nuclei expressed similar morphological properties, indicating that they were probably in the same stage of the nuclear cycle, they revealed highly variable chromatin densities. Electron microscope (EM) analysis of the cytoplasm of cleavage-arrested cells revealed the accumulation of vesicles and large membranous elements coincident with cleavage arrest. Furthermore, endoplasmic reticulum (ER) existed in two forms, as closed, circular profiles and as long, linear arrays. Mitochondria were characteristically aligned in single file on both sides of the two types of ER cisternae. EM analysis of nuclei confirmed variations in chromatin organization and suggested the occurrence of unique nuclear envelope fusion among micronuclei in cleavage-arrested cells. Cleavage arrest and changes in cytological features were not observed in the cytoplasm of cells microinjected with normal rat IgG. Thus the immunochemical data and microinjection experiments suggest that ras-like or ras antigenicity exists within rapidly replicating Xenopus blastomeres and may be involved in the organization of a number of its cytoplasmic elements.

Animals↗

PubMed2001

Expression of a reporter gene after microinjection of mammalian artificial chromosomes into pronuclei of bovine zygotes.

The introduction of mammalian artificial chromosomes (ACs) into zygotes represents an alternative, more predictive technology for the production of recombinant proteins in transgenic animals. The aim of these experiments was to examine the effects of artificial chromosome microinjection into bovine pronuclei on embryo development and reporter gene expression. Bovine oocytes aspirated from 2-5 mm size follicles were matured in vitro for 22 hr. Mature oocytes were fertilized in vitro with frozen- thawed bull spermatozoa. Artificial chromosome carrying either beta-galactosidase (Lac-Z) gene or green fluorescence protein (GFP) gene were isolated by flow cytometry. A single chromosome was microinjected into one of the two pronuclei of bovine zygotes. Sham injected zygotes served as controls. Injected zygotes were cultured in G 1.2 medium for 7 days. Hatched blastocysts were cultured on blocked STO cell feeder layer for attachment and outgrowth of ICM and trophectoderm cells. The results showed a high zygote survival rate following LacZ-ACs microinjection (74%). However, the blastocyst development rate after 7 days of culture was significantly lower than that of sham injected zygotes (7.5 vs. 22%). Embryonic cells positive for Lac-Z gene were detected by PCR in three of nine outgrowth colonies. In addition, GFP gene expression was observed in 15 out of 85 (18%) embryos at the arrested 2-cell stage to blastocyst stage. Six blastocysts successfully outgrew, three outgrowths were GFP positive for up to 3 weeks in culture. We conclude that the methodology for artificial chromosome delivery into bovine zygotes could lead to viable blastocyst development, and reporter gene expression could be sustained during pre-implantation development.

Animals↗

PubMed1987

DNA synthesis following microinjection of heterologous sperm and somatic cell nuclei into hamster oocytes.

We have investigated the ability of the hamster oocyte to initiate DNA synthesis in nuclei differing in basic protein content. DNA synthesis was studied by autoradiography in oocytes that had been incubated in 3H-thymidine after being parthenogenetically activated by sham microinjection, or microinjected with hamster, mouse, rabbit, or fish sperm nuclei, or hamster hepatocyte nuclei. Within 6 hr of sham or nucleus microinjection, nuclei of each type underwent transformation into pronuclei and synthesized DNA. These results demonstrated that the hamster egg can access and utilize its own and each type of template provided, whether homologous or heterologous. However, pronuclei derived from hamster sperm nuclei were more likely to be synthesizing DNA at 6 hr than pronuclei derived from sperm nuclei of other species. We conclude that the mechanisms employed by the hamster oocyte to transform hamster sperm nuclei into pronuclei and to effect DNA synthesis in these nuclei are not specific for the hamster sperm nucleus. Nevertheless, these mechanisms apparently operate more efficiently when the hamster sperm nucleus, rather than a heterologous sperm nucleus, is present.

Animals↗

PubMed1988

Flow sorting of X and Y chromosome-bearing mammalian sperm: activation and pronuclear development of sorted bull, boar, and ram sperm microinjected into hamster oocytes.

Flow cytometric techniques were used to measure relative DNA content of X and Y chromosome-bearing bull, boar, and ram sperm populations and to separate the two sex-determining populations. Neat semen was prepared for flow cytometric analysis by washing, light sonication, and staining with 9 microM Hoechst 33342. Computer analysis of the bimodal histograms showed mean X-Y DNA differences of 3.9, 3.7, and 4.2% for bull, boar, and ram, respectively. Flow cytometric reanalysis of sorted bull, boar, and ram sperm showed purities greater than 90%. Bull, boar, and ram sperm nuclei were microinjected into hamster oocytes. Microinjected sperm were either unsorted, sorted, unsorted plus dithiothreitol (DTT) exposure, or sorted plus DTT exposure. Following microinjection, eggs were incubated 3 hr, fixed, and stained. A total of 579 eggs was observed for sperm activation (decondensation or formation of a male pronucleus). A lower percentage of sorted than unsorted (3 vs. 23%) boar sperm was activated (P less than .05). However, sorted and unsorted DTT-exposed boar sperm or sorted and unsorted bull or ram sperm, regardless of DTT treatment, did not differ significantly. Sorted sperm nuclei of both rams and bulls exhibited higher activation rates than sorted boar sperm (P less than .05). Treatment of sperm with DTT increased the activation rate (P less than .05) for sorted boar sperm but not for bull or ram sperm.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed2003

Intrastriatal microinjection of sodium nitroprusside induces cell death and reduces binding of dopaminergic receptors.

Rat striatum was microinjected with 50 nmol sodium nitroprusside (SNP) and neural cell death as well as the binding of dopaminergic receptors were followed for 24 h after the infusion using TTC staining, cresyl violet staining, and quantitative autoradiography. Striatal cell death was observed 3 h after the infusion of SNP. A widespread area of cell death, including part of the cerebral cortex, was seen at 24 h after the infusion. A decrease of more than 80% in dopamine D1 receptor binding was seen in rat brain slices prepared 2 h after the infusion of SNP, whereas only a slight decrease in dopamine D2 receptor binding and almost no changes in dopamine transporter binding were observed. One day after the infusion, less than 10% of the binding of all three types of dopaminergic receptors remained in a widespread area in the infused side of the striatum and part of the cerebral cortex. Microinjection of either NOC-18 (50 nmol), another type of NO donor, or sodium cyanide (50 nmol) did not caused cell death. In addition, microinjection of FeCl2 (50 nmol) into the striatum caused cell death and reduction in dopamine D() receptor binding. These results suggest that iron-related radical reactions, but not NO itself, might have important roles on SNP-caused cell death. The current receptor binding study also indicated that dopamine D1 receptor binding is the most sensitive indicator for detection of cell death or cell damage induced by radical reactions in the rat striatum.

Animals↗

PubMed1991

Effects of QA 208-199 and its metabolite 209-668 on embryonic development in vitro after microinjection into the exocoelomic space or into the amniotic cavity of cultured rat conceptuses.

The objective of this study was to determine the direct embryotoxic effects in vitro of N-hydroxy-N-methyl-7-propoxy-2-naphthalene-ethanamine (QA 208-199, QAB) and of one of its metabolites, 7-propoxy-naphthalene-2-ylacetic acid (209-668, QAA), after circumventing the bioconverting conceptual membranes. The compounds were, therefore, microinjected either into the exocoelomic space or into the amniotic cavity of rat conceptuses of 10 d at prenatal age at doses of up to 84.9 ng (QAA) and 180 ng (QAB) per conceptus respectively. The conceptuses were subsequently cultured for 28 h after which their development was assessed. QAB produced marginal effects on embryonic differentiation only after microinjection of the compound into the amniotic cavity. Dysmorphogenic effects, however, occurred in a dose-dependent fashion after either exocoelomic or intraamniotic microinjections of the compound. The frequencies and types of anomalies were similar after either exposure route and consisted predominantly of anomalies associated with axial rotation. QAA also impaired embryonic differentiation at only the high dose level of 84.9 ng per embryo and after intraamniotic injections only. Dysmorphogenic effects were observed in all experimental groups, although the differences were not statistically significant when compared with the concomitant controls. An increased proportion of anomalies observed were in the cephalic region as compared to the defects produced by QAB. These data suggest that QAA most probably is not the QAB metabolite responsible for the embryotoxic action of QAB in vitro. Furthermore, the results tend to confirm the suggested involvement of the visceral yolk sac membrane in mediating QAB embryotoxicity.

Amnion↗

PubMed1995

Effect of microinjection of rap 2A point mutant proteins on maturation and mottling in Xenopus oocytes.

We have analyzed the morphological alterations induced in Xenopus oocytes as a consequence of the microinjection of rap 2A proteins with point mutations at critical positions in the functional domains defined for members of the ras superfamily. Ala 35 rap 2A, a point mutation in the "effector" domain, is able to induce the rearrangement of the pigments in the animal hemisphere termed "mottling". This characteristic phenotype is delayed in asn 17 rap 2A and wild-type rap 2A proteins. A completely different phenotype appears as a consequence of the microinjection of Val 12-rap 2A. This mutant is able to trigger oocyte maturation and is less efficient inducing mottling than Ala 35 or wild-type rap 2A proteins. Neither of these rap 2A mutant proteins is able to counteract ras-induced maturation. However there is a striking interference with progesterone-induced maturation, since wild-type or val 12 rap 2A microinjection reduced the viability of progesterone-treated oocytes. These findings suggest that rap2A proteins are regulatory elements in distinct signal transduction pathways that either lead to the morphological changes associated with the phenotype "mottling" or to oocyte maturation.

Animals↗

PubMed1998

Rapid determination of gap junction formation using HeLa cells microinjected with cDNAs encoding wild-type and chimeric connexins.

A procedure for rapidly determining the functionality of gap junctions constructed of recombinant connexins in communication-deficient HeLa cells is described. Nuclear microinjection of cDNA encoding wild-type connexins (Cx) 26, 32, 43, and a range of connexin-aequorin (Cx-Aeq) chimerase resulted in generation of gap junction intercellular communication channels. Expression of recombinant protein was detected in > 95% of cells 18-72 h following nuclear microinjection, and the functionality of the channels generated was determined according to their ability to transfer the fluorescent dye tracers Lucifer yellow and propidium iodide. The dye transfer results obtained correlated closely with other published studies using stably transfected cells and yet are obtained as rapidly as 18 h following microinjection of cDNA. Expression of a truncated form of Cx43 (Cx43 delta 244) by this new method indicated diminished intercellular transfer of both dyes and supports a channel-gating mechanism that postulates interaction between the carboxyl tail and the intracellular loop.

Aequorin↗

PubMed1998

Efficient and stable gene transfer following microinjection into nuclei of synchronized animal cells progressing from G1/S boundary to early S phase.

We examined the possible phase(s) of the cell cycle in which a foreign gene can be stably transferred to animal cells. DNA of the plasmid pSV2neo containing the neomycin-phosphotransferase gene was microinjected into the nuclei of NIH/3T3 cells synchronized by serum starvation and aphidicolin treatment. The frequency of neo(r)-transformation (expressed as a percentage of microinjected cells) was 6% at the G0 phase and increased with progression of the cell cycle to reach a peak of 76% at the G1/S boundary. When the cells started their growth from the G1/S following release from aphidicolin, the frequency increased or decreased in the parallel with the BrdU-labeling index. Furthermore we developed a simplified method in which asynchronously growing cells were treated with aphidicolin at 10 micrograms/ml fro 16 hrs without serum starvation and subjected to microinjection, and their growth was further induced in aphidicolin-free medium. Using five cell lines (BALB/3T3, BALB/MK-2, NRK, CHO-K1, and HeLa) and one primary culture of chicken embryo fibroblasts (CEF), a 3- to 7-fold increase in the frequency of neo(r)-transformation was consistently detected in aphidicolin-treated cells, compared to non-treated asynchronous cultures. The present study indicates that synchronized animal cells progressing from the G1/S boundary to the early S phase integrate the PSV2neo DNA into their chromosomes with high efficiency.

3T3 Cells↗

PubMed2000

Overcoming a permeability barrier by microinjecting cryoprotectants into zebrafish embryos (Brachydanio rerio).

The goal of this research was to examine the developmental effects on zebrafish embryos (Brachydanio rerio) when cryoprotectants were directly microinjected into the yolk. Our objectives were to: (i) determine the final concentration of propylene glycol (PG) and dimethyl sulfoxide (Me(2)SO) that the embryos could tolerate without causing teratogenic effects; (ii) determine if the toxicity of Me(2)SO could be reduced by the simultaneous presence of various proportions of amides; and (iii) examine whether this intracellular cryoprotectant incorporation could reduce the cryodamage to the yolk syncytial layer (YSL) after vitrification trials. The rationale for conducting these microinjection experiments was to overcome the permeability barrier of the YSL. Intracellular PG produced better survival than Me(2)SO (P < 0.05). Embryos tolerated both 10- and 30-nl microinjections of PG, yielding final concentrations of 2.3 and 5.0 M within the yolk, resulting in 70 +/- 3 and 35 +/- 4% survival at day 5, respectively. In similar experiments with Me(2)SO, survival was lower than PG at 60 +/- 4 and 14 +/- 4% at 2.4 and 5.2 M. Unlike other cellular systems, the presence of amides, specifically acetamide or formamide, did not reduce the toxicity of Me(2)SO in zebrafish embryos (P > 0.05). During vitrification trials, we estimated a 25% dehydration of the yolk, yielding an effective PG concentration of 5.9 M. However, the incorporation of this vitrifiable concentration of PG was not sufficient to improve the postthaw morphology of the YSL (P > 0.05). Clearly, other factors need to be examined in establishing a successful vitrification protocol for zebrafish embryos.

Acetamides↗

PubMed2000

Induction of early transcription in one-cell mouse embryos by microinjection of the nonhistone chromosomal protein HMG-I.

In the mouse embryo, the onset of zygotic transcription occurs at the end of the first cell cycle, upon completion of DNA replication. We show that the nonhistone chromosomal protein HMG-I, whose translocation into the pronuclei of one-cell embryos is linked to this first round of DNA synthesis, plays a critical role in the activation of zygotic transcription. Indeed, microinjection of purified HMG-I results in a higher nuclear accumulation of the protein and triggers an earlier activation of zygotic transcription, an effect which is abolished by the preincubation of the protein with a specific antibody directed against its AT-hook DNA-binding motifs. Significantly, microinjection of this antibody also prevents the normal onset of transcription in the embryo, suggesting that endogenous HMG-I is similarly involved in this process. Finally, microinjection of the exogenous protein modifies chromatin structure as measured by in situ accessibility to DNase I. We propose that general chromosomal architectural factors such as HMG-I can modulate the accessibility of chromatin to specialized regulatory factors, thereby promoting a transcriptionally competent state.

Animals↗

PubMed1998

Neurotoxic effects of fractionated diesel exhausts following microinjections in rat hippocampus and striatum.

Exhaust emissions from a heavy-duty diesel vehicle, separated into particulate and semivolatile phases and thereafter fractionated according to polarity, were studied in the adult rat brain after intracranial microinjections using cresyl violet staining and immunohistochemistry. Intrastriatal as well as intrahippocampal injections of particulate fractions III [containing mononitro-polycyclic aromatic hydrocarbon (PAH)], IV (dinitro-PAH and quinones) and V (polar material) and of semivolatile fractions IV and V, in amounts corresponding to a driven length of 19.5 m, caused major lesions with tissue loss and disappearance of immunoreactivity for glial fibrillary acidic protein, tyrosine hydroxylase, and acetylcholine esterase. Particulate fractions I ("light" aliphatic hydrocarbons) and II ("heavy" aliphatic hydrocarbons and PAH) and semivolatile fraction III produced smaller lesions; semivolatile fractions I and II led to lesions equivalent to those of the vehicle dimethyl sulfoxide alone. Microinjected doses of particulate fractions III or IV corresponding to driven lengths of 2.0 and 9.8 m produced a variable lesion. Thus, fractions containing nitro-derivatives of PAH, quinones, and polar material caused the greatest damage after intracranial injections. It is concluded that intracerebral microinjections of fractionated motor vehicle exhausts provide a method for systematic testing of direct neurotoxicity.

Animals↗

PubMed1993

Microinjection of intact 200- to 500-kb fragments of YAC DNA into mammalian cells.

DNA of yeast artificial chromosomes (YACs) was prepared for microinjection by separation from most of the natural yeast chromosomes on a pulsed-field gel, treatment with agarase, and centrifugation. A salt concentration of 100 mM NaCl was necessary to protect the DNA from shear during these procedures. Injection of a 590-kb YAC, yGART2, into Chinese hamster ovary cells gave rise to cells expressing the 40-kb human GART gene carried on the YAC. Nine of 12 cell lines analyzed contained an intact stretch of at least 110 kb of YAC DNA surrounding the GART gene, and one cell line contained at least 480 kb, but not the entire 590 kb, intact. Mouse L A-9 cells were similarly injected with DNA of a 230-kb YAC containing the human beta-globin gene cluster and a mammalian selectable marker. Seven of 10 of the resulting cell lines contained both YAC vector arms plus the intact 140-kb SfiI fragment spanning the beta-globin gene. Three cell lines were analyzed by RecA-assisted restriction endonuclease (RARE) cleavage and found to contain the entire intact 210-kb YAC insert. Introduction of similarly prepared DNA into mammalian cells by lipofection gave rise to cell lines with multiple YAC fragments that were generally shorter than the YAC fragments found in microinjected cell lines. The results show that microinjection of gel-purified YAC DNA into mammalian cells is an efficient method of transferring DNA fragments several hundred kilobase pairs in size into mammalian cells.

Animals↗

PubMed2002

Microinjection of DNA into the nuclei of human vascular smooth muscle cells.

BACKGROUND: It is challenging to successfully transfect human vascular cells by conventional techniques. We evaluated the efficiency of transfection of human smooth muscle cells (SMC) using a method of direct nuclear microinjection of DNA constructs. MATERIALS AND METHODS: The nuclei of explanted human saphenous vein SMC were microinjected with the plasmid pCMVbeta, containing the lacZ gene for beta-galactosidase (beta-gal). Efficiency of injection and expression were assessed by histochemical staining for beta-gal. Injected SMC were subjected to standard assays of viability and migration. RESULTS: Parameters affecting the conditions of injection were systematically analyzed to achieve optimal transfection efficiency. A vertical injection resulted in a twofold increase in expression of beta-gal compared to a horizontal approach. A DNA concentration of 100 ng/microl (390 copies/injection) provided a maximal rate of expression. No further increase in expression was evident at higher concentrations. Maximal expression was achieved with a time of injection of 200-500 ms, an injection pressure of 5-10 psi, and a pipette tip size of 0.6 microm, resulting in an injection volume of 0.03 pl. Cytoplasmic injection did not result in gene expression. The ability of SMC to migrate under videomicroscopy was not altered by the injection process. Optimizing all injection parameters resulted in cell viability >95% and efficiency of injection of 59%. CONCLUSION: DNA encoding a variety of intracellular proteins can be efficiently microinjected into human vascular SMC. Coupled with the use of videomicroscopy, this technique can allow for the evaluation of genes that might modulate important cellular processes such as proliferation and migration.

Cell Movement↗

PubMed1993

Tremor reduction by microinjection of lidocaine during stereotactic surgery.

We report our experience with lidocaine microinjection into the thalamus in 10 patients undergoing stereotactic thalamotomy for the treatment of Parkinsonian or non-Parkinsonian tremor. 18 injection sites in 4 patients with Parkinson's disease and 22 sites in 6 patients with other forms of tremor have been compared with respect to the effect of microstimulation. In over two thirds of cases the test microinjection replicated the effects of microstimulation. Long term follow up will be required to determine whether lesions made on the basis of lidocaine induced tremor suppression will result in a lower rate of tremor recurrence than those based on stimulation induced tremor suppression. In those patients in whom stimulation induced tremor suppression occurs but tremor arrest cannot be produced with lidocaine microinjection, chronic thalamic stimulation may be an alternative for the long term control of tremor in these patients.

Electric Stimulation Therapy↗

PubMed1992

Effects on the chicken monocular OKN of unilateral microinjections of GABAA antagonist into the mesencephalic structures responsible for OKN.

The SR 95531, a GABAA antagonist was microinjected into either the pretectum nuclei, (nucleus Superficialis Synencephali nSS) or the nBOR (nucleus Ectomammillaris nEM) of chickens. Monocular optokinetic nystamus (OKN) of each eye was recorded by the search coil technique before and after unilateral intracerebral drug administration. Before injection, monocular horizontal OKN in chickens, as in other lower vertebrates, displays a directional asymmetry: the stimulation in the Temporo-Nasal (T-N) direction is more efficient in evoking OKN than is stimulation in the Naso-Temporal (N-T) direction. Unilateral microinjections of SR 95531 into either the nSS or nEM induce a reversible increase of gain in OKN directed by the contralateral eye for both directions of stimulation. However administration into the nSS increased directional asymmetry by increasing the T-N component slow phase velocity more strongly than the N-T component slow phase velocity. On the other hand, the unilateral administration of the drug into the nEM suppressed the directional OKN asymmetry by increasing the N-T component slow phase velocity more strongly than the T-N component slow phase velocity. These results indicate that the drug suppresses GABAergic inhibition at the mesencephalic level. Moreover the nSS seems especially involved in monocular OKN in response to a T-N stimulation, while the nEM seems more involved in the OKN response to N-T stimulation. The increase in gain of OKN directed by the ipsilateral eye to microinjected nuclei could account for the strong interactions existing between these mesencephalic structures responsible for horizontal OKN.

Animals↗