Effects of light isoflurane anesthesia on organization of direction and orientation selectivity in the superficial layer of the mouse superior colliculus

We have recently found that GABAC receptor subunit transcripts are expressed in the superficial layers of rat superior colliculus (SC). In the present study we used immunocytochemistry to demonstrate the presence of GABAC receptors in rat SC at protein level. We also investigated in acute rat brain slices the effect of GABAA and GABAC receptor agonists and antagonists on stimulus-evoked extracellular field potentials in SC. Electrical stimulation of the SC optic layer induced a biphasic, early and late, potential in the adjacent superficial layer. The late component was completely inhibited by 6-cyano-7-nitroquinoxaline-2,3-dione or CoCl2, indicating that it was generated by postsynaptic activation. Muscimol, a potent GABAA and GABAC receptor agonist, strongly attenuated this postsynaptic potential at concentrations >10 μM. In contrast, the GABAC receptor agonist cis-aminocrotonic acid, as well as muscimol at lower concentrations (0.1–1 μM) increased the postsynaptic potential. This increase was blocked by (1,2,5,6-tetrahydropyridine-4-yl)methylphosphinic acid, a novel competitive antagonist of GABAC receptors. Our findings demonstrate the presence of functional GABAC receptors in SC and suggest a disinhibitory role of these receptors in SC neuronal circuitry.

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Effects of norepinephrine upon superficial layer neurons in the superior colliculus of the hamster: In vitro studies

Visual Neuroscience ◽

10.1017/s0952523899163156 ◽

1999 ◽

Vol 16 (3) ◽

pp. 557-570 ◽

Cited By ~ 9

Author(s):

HONGJING TAN ◽

RICHARD D. MOONEY ◽

ROBERT W. RHOADES

Keyword(s):

Superior Colliculus ◽

Optic Tract ◽

Reversal Potential ◽

Outward Current ◽

Input Resistance ◽

Superficial Layer ◽

Membrane Properties ◽

Induced Response

Intracellular recording techniques were used to evaluate the effects of norepinephrine (NE) on the membrane properties of superficial layer (stratum griseum superficiale and stratum opticum) superior colliculus (SC) cells. Of the 207 cells tested, 44.4% (N = 92) were hyperpolarized by ≥3 mV and 8.7% (N = 18) were depolarized by ≥3 mV by application of NE. Hyperpolarization induced by NE was dose dependent (EC50 = 8.1 μM) and was associated with decreased input resistance and outward current which had a reversal potential of −94.0 mV. Depolarization was associated with a very slight rise in input resistance and had a reversal potential of −93.1 mV for the single cell tested. Pharmacologic experiments demonstrated that isoproterenol, dobutamine, and p-aminoclonidine all hyperpolarized SC cells. These results are consistent with the conclusion that NE-induced hyperpolarization of SC cells is mediated by both α2 and β1 adrenoceptors. The α1 adrenoceptor agonists, methoxamine and phenylephrine, depolarized 35% (6 of 17) of the SC cells tested by ≥3 mV. Most of the SC cells tested exhibited responses indicative of expression of more than one adrenoceptor. Application of p-aminoclonidine or dobutamine inhibited transsynaptic responses in SC cells evoked by electrical stimulation of optic tract axons. Inhibition of evoked responses by these agents was usually, but not invariably, associated with a hyperpolarization of the cell membrane and a reduction in depolarizing potentials evoked by application of glutamate. The present in vitro results are consistent with those of the companion in vivo study which suggested that NE-induced response suppression in superficial layer SC neurons was primarily postsynaptic and chiefly mediated by both α2 and β1 adrenoceptors.

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Response Recovery Cycles in the Visual Cortex and Superior Colliculus Following Conditioning ‘ON” and ‘OFF” Stimulation in the Rabbit

Canadian Journal of Neurological Sciences / Journal Canadien des Sciences Neurologiques ◽

10.1017/s0317167100120384 ◽

1977 ◽

Vol 4 (1) ◽

pp. 31-37 ◽

Cited By ~ 2

Author(s):

Stéphane Molotchnikoff ◽

Michel Dubuc

Keyword(s):

Visual Cortex ◽

Superior Colliculus ◽

Conditioning Stimulus ◽

Superficial Layer ◽

Evoked Responses ◽

Ventral Part ◽

Response Recovery ◽

Optic Nerve Stimulation ◽

Recovery Cycles ◽

Conditioning Stimuli

SummaryThe responsiveness of the visual cortex (VC) and superior colliculus (SC) was simultaneously compared following conditioning “ON” or “OFF” stimulation, in the rabbit.Average evoked responses were recorded simultaneously from the visual cortex and superior colliculus. “ON” or “OFF” steps constituted the conditioning stimuli whereas the test stimulus consisted of optic nerve stimulation. All evoked responses exhibited a reversal of their polarity when the electrode was moved in the dorsoventral direction (Negative-Positive in the SC, Positive-Negative in the VC). This assured the somato-dentritic origin of the potentials. The results showed that responsiveness in both structures was significantly higher following an “OFF” stimulus than after an “ON” step. Collicular responsiveness was higher than in the VC when the same conditioning stimulus was applied. The spatial distribution of the source of “OFF” responses was circumscribed to the ventral part of the superficial layer of the superior colliculus. These results suggest specific properties associated with the brightening and dimming systems.

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Organization of monkey superior colliculus: intermediate layer cells discharging before eye movements

Journal of Neurophysiology ◽

10.1152/jn.1976.39.4.722 ◽

1976 ◽

Vol 39 (4) ◽

pp. 722-744 ◽

Cited By ~ 227

Author(s):

C. W. Mohler ◽

R. H. Wurtz

Keyword(s):

Eye Movements ◽

Superior Colliculus ◽

Eye Movement ◽

Intermediate Layer ◽

Visual Fields ◽

Saccadic Eye Movements ◽

Superficial Layer ◽

Cell Discharge ◽

Intermediate Layers ◽

Dorsal Edge

1. We investigated the characteristics of cells in the intermediate layers of the superior colliculus that increase their rate of discharge before saccadic eye movements. Eye movements were repeatedly elicited by training rhesus monkeys to fixate on a spot of light and to make saccades to other spots of light when the fixation spot was turned off. 2. The eye movement cells showed consistent variations with their depth within the colliculus. The onset of the cell discharge led the eye movement by less time and the duration of the discharge was shorter as the cell was located closer to the dorsal edge of the intermediate layers. The movements fields (that area of the visual field where a saccade into the area is preceded by a burst of cell discharges) of each successive cell also became smaller as the cells were located more dorsally. The profile of peak discharge frequency remained fairly flat throughout the movement field of the cells regardless of depth of the cell within the colliculus. 3. A new type of eye movement-related cell has been found which usually lies at the border between the superficial and intermediate layers. This cell type, the visually triggered movement cell, increased its rate of discharge before saccades made to a visual stimulus but not before spontaneous saccades of equal amplitude made in the light or the dark. A vigorous discharge of these cells before an eye movement was dependent on the presence of a visual target; the cells seemed to combine the visual input of superficial layer cells and the movement-related input of the intermediate layer cells. The size of the movement fields of these cells were about the same size as the visual fields of superficial layer cells just above them...

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Effects of serotonin on retinotectal-, corticotectal-, and glutamate-induced activity in the superior colliculus of the hamster

Journal of Neurophysiology ◽

10.1152/jn.1993.70.2.723 ◽

1993 ◽

Vol 70 (2) ◽

pp. 723-732 ◽

Cited By ~ 28

Author(s):

X. Huang ◽

R. D. Mooney ◽

R. W. Rhoades

Keyword(s):

Superior Colliculus ◽

Optic Chiasm ◽

Superficial Layer ◽

Response Suppression ◽

Visual Response ◽

Evoked Responses ◽

Average Response ◽

Visual Responses ◽

Unit Recording ◽

Visual Cortical

1. Single-unit recording and iontophoretic techniques were used to test the effects of serotonin (5-HT) on the responses of neurons in the superficial layers (the stratum griseum superficiale and stratum opticum) of the hamster's superior colliculus (SC). 2. Iontophoresis of 5-HT produced a visual response suppression of 40% or greater in 78.1% (n = 50) of 64 neurons tested. 5-HT did not augment the visual responses of any of the cells tested. The average response suppression was 75.3 +/- 21.2% (mean +/- S.D.). 3. Iontophoresis of 5-HT had significantly different effects on activation of SC cells by optic chiasm (OX) and visual cortical (CTX) stimulation. Application of 5-HT suppressed the OX-evoked responses of 96.9% (n = 31) of the 32 SC cells tested by at least 40%, and the average response suppression for all 32 neurons tested was 87.1 +/- 22.5%. Application of 5-HT suppressed the responses of only 35.7% (n = 10) of the 28 cells tested with CTX stimulation by at least 40%. The average response suppression for all 28 cells was 35.3 +/- 38.8%. 4. The effects of 5-HT on the glutamate-evoked responses of SC cells that were synaptically "isolated" by concurrent application of Mg2+ were also evaluated. Application of 5-HT produced a response suppression > or = 40% in 29.7% (n = 19) of the 64 neurons tested under these conditions. The average response suppression for all of the cells tested was 28.4 +/- 35.7%. This effect of 5-HT was significantly weaker than that on visually evoked responses of these neurons. 5. The present results demonstrate that 5-HT markedly depresses the visual responses of most superficial layer SC neurons. They suggest further that much of this effect is mediated by presynaptic inhibition of retinotectal transmission.

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Effects of angiotensin II on visual neurons in the superficial laminae of the hamster's superior colliculus

Visual Neuroscience ◽

10.1017/s0952523800006969 ◽

1994 ◽

Vol 11 (6) ◽

pp. 1163-1173 ◽

Cited By ~ 13

Author(s):

Richard D. Mooney ◽

Yi Zhang ◽

Robert W. Rhoades

Keyword(s):

Electrical Stimulation ◽

Angiotensin Ii ◽

Superior Colliculus ◽

Visual Stimulation ◽

Optic Chiasm ◽

Superficial Layer ◽

Receptor Subtypes ◽

Visual Responses ◽

Visual Neurons ◽

Stimulation Of

AbstractSuperficial layer superior colliculus (SC) neurons were recorded extracellularly with multibarreled recording/ejecting micropipettes. Angiotensin II was delivered via micropressure ejection during visual stimulation (n = 215 cells), or during electrical stimulation of either the optic chiasm (OX; n = 150 cells) or visual cortex (CTX; n = 42 cells). Application of angiotensin II decreased visual responses of SC cells to 43.8% ± 30.7% (mean ± S.D.) and reduced responses to electrical stimulation of the OX and CTX to 58.6% ± 34.1% and 43.8% ± 30.7% of control values, respectively. Angiotensin II enhanced responses by at least 30% in only 6 cells (1.5%). Of the 35 neurons tested with both OX and CTX stimulation, the correlation of evoked response suppression by angiotensin II was highly significant (r = 0.69; P < 0.001). This suggests that the suppressive effects of angiotensin II were common to both pathways. To test whether the inhibitory effects of angiotensin II were presynaptic or postsynaptic, Mg2+ ions were ejected iontophoretically to abolish synaptic responses, and the neurons were activated by iontophoresis of glutamate and then tested with angiotensin II. Angiotensin II reduced the glutamate-evoked responses to an average 29.1% ± 21.1% of control values (n = 9 cells). This suggests that the site of action of angiotensin II is most likely postsynaptic. To identify which receptors were involved in these effects, angiotensin II was ejected concurrently with the AT1 antagonist Losartan (DUP753) or with either of two AT2 antagonists, CGP42112A or PD123177. Losartan antagonized the action of angiotensin II in 65.6% of the cells tested (n = 99) and CGP42112A and PD123177 had antagonistic effects in 58% (n = 65) and 60% (n = 5), respectively. Both classes of antagonists were tested in 29 cells; and there was no significant correlation between their effectiveness. These results suggest that both AT1, and AT2 receptors may independently mediate the suppressive effects of angiotensin II, and that collicular neurons may have either or both receptor subtypes.

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Neurons in the monkey superior colliculus predict the visual result of impending saccadic eye movements

Journal of Neurophysiology ◽

10.1152/jn.1995.73.5.1988 ◽

1995 ◽

Vol 73 (5) ◽

pp. 1988-2003 ◽

Cited By ~ 221

Author(s):

M. F. Walker ◽

E. J. Fitzgibbon ◽

M. E. Goldberg

Keyword(s):

Receptive Field ◽

Superior Colliculus ◽

Eye Movement ◽

Receptive Fields ◽

Saccadic Eye Movements ◽

Superficial Layer ◽

Saccade Target ◽

Visual Response ◽

Intermediate Layers ◽

Movement Field

1. Previous experiments have shown that visual neurons in the lateral intraparietal area (LIP) respond predictively to stimuli outside their classical receptive fields when an impending saccade will bring those stimuli into their receptive fields. Because LIP projects strongly to the intermediate layers of the superior colliculus, we sought to demonstrate similar predictive responses in the monkey colliculus. 2. We studied the behavior of 90 visually responsive neurons in the superficial and intermediate layers of the superior colliculus of two rhesus monkeys (Macaca mulatta) when visual stimuli or the locations of remembered stimuli were brought into their receptive fields by a saccade. 3. Thirty percent (18/60) of intermediate layer visuomovement cells responded predictively before a saccade outside the movement field of the neuron when that saccade would bring the location of a stimulus into the receptive field. Each of these neurons did not respond to the stimulus unless an eye movement brought it into its receptive field, nor did it discharge in association with the eye movement unless it brought a stimulus into its receptive field. 4. These neurons were located in the deeper parts of the intermediate layers and had relatively larger receptive fields and movement fields than the cells at the top of the intermediate layers. 5. The predictive responses of most of these neurons (16/18, 89%) did not require that the stimulus be relevant to the monkey's rewarded behavior. However, for some neurons the predictive response was enhanced when the stimulus was the target of a subsequent saccade into the neuron's movement field. 6. Most neurons with predictive responses responded with a similar magnitude and latency to a continuous stimulus that remained on after the saccade, and to the same stimulus when it was only flashed for 50 ms coincident with the onset of the saccade target and thus never appeared within the cell's classical receptive field. 7. The visual response of neurons in the intermediate layers of the colliculus is suppressed during the saccade itself. Neurons that showed predictive responses began to discharge before the saccade, were suppressed during the saccade, and usually resumed discharging after the saccade. 8. Three neurons in the intermediate layers responded tonically from stimulus appearance to saccade without a presaccadic burst. These neurons responded predictively to a stimulus that was going to be the target for a second saccade, but not to an irrelevant flashed stimulus. 9. No superficial layer neuron (0/27) responded predictively when a stimulus would not be brought into their receptive fields by a saccade.(ABSTRACT TRUNCATED AT 400 WORDS)

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Activation and Inactivation of Rostral Superior Colliculus Neurons During Smooth-Pursuit Eye Movements in Monkeys

Journal of Neurophysiology ◽

10.1152/jn.2000.84.2.892 ◽

2000 ◽

Vol 84 (2) ◽

pp. 892-908 ◽

Cited By ~ 57

Author(s):

Michele A. Basso ◽

Richard J. Krauzlis ◽

Robert H. Wurtz

Keyword(s):

Eye Movements ◽

Superior Colliculus ◽

Smooth Pursuit ◽

Superficial Layer ◽

Smooth Pursuit Eye Movements ◽

Pursuit Eye Movements ◽

Pursuit Initiation ◽

Intermediate Layers ◽

Deep Layers ◽

Stimulation Of

Neurons in the intermediate and deep layers of the rostral superior colliculus (SC) of monkeys are active during attentive fixation, small saccades, and smooth-pursuit eye movements. Alterations of SC activity have been shown to alter saccades and fixation, but similar manipulations have not been shown to influence smooth-pursuit eye movements. Therefore we both activated (electrical stimulation) and inactivated (reversible chemical injection) rostral SC neurons to establish a causal role for the activity of these neurons in smooth pursuit. First, we stimulated the rostral SC during pursuit initiation as well as pursuit maintenance. For pursuit initiation, stimulation of the rostral SC suppressed pursuit to ipsiversive moving targets primarily and had modest effects on contraversive pursuit. The effect of stimulation on pursuit varied with the location of the stimulation with the most rostral sites producing the most effective inhibition of ipsiversive pursuit. Stimulation was more effective on higher pursuit speeds than on lower and did not evoke smooth-pursuit eye movements during fixation. As with the effects on pursuit initiation, ipsiversive maintained pursuit was suppressed, whereas contraversive pursuit was less affected. The stimulation effect on smooth pursuit did not result from a generalized inhibition because the suppression of smooth pursuit was greater than the suppression of smooth eye movements evoked by head rotations (vestibular-ocular reflex). Nor was the stimulation effect due to the activation of superficial layer visual neurons rather than the intermediate layers of the SC because stimulation of the superficial layers produced effects opposite to those found with intermediate layer stimulation. Second, we inactivated the rostral SC with muscimol and found that contraversive pursuit initiation was reduced and ipsiversive pursuit was increased slightly, changes that were opposite to those resulting from stimulation. The results of both the stimulation and the muscimol injection experiments on pursuit are consistent with the effects of these activation and inactivation experiments on saccades, and the effects on pursuit are consistent with the hypothesis that the SC provides a position signal that is used by the smooth-pursuit eye-movement system.

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