Effects of choline and other nicotinic agonists on the tectum of juvenile and adult Xenopus frogs: a patch-clamp study

Titmus, Margaret; Tsai, Hao-Jan; Lima, R.; Udin, Susan B.

doi:10.1016/s0306-4522(98)00625-3

Cited by 41 publications

(51 citation statements)

References 66 publications

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“…We cannot rule out the possibility that the soma of cells in which no nicotine-induced increase in sPSCs was recorded were electrically isolated from their retinal input. However, the evoking of this response in only a subset of cells is consistent with previous observations that antibodies against nicotinic receptors bind to some but not all of the tectal layers that contain retinal ganglion cell terminals (Sargent et al, 1989;Titmus et al, 1999).…”

Section: Nicotinic Receptor Location In the Optic Tectumsupporting

confidence: 91%

“…Responses were analyzed in 8-s bin widths to obtain peak frequency values and response-duration measurements. The change in peak frequency was calculated using the following formula: (peak frequency with the agonist −peak frequency before the agonist)/(peak frequency with the agonist+peak frequency before the agonist) (Titmus et al, 1999). One-second bin widths were used to determine half-peak latencies.…”

Section: Methodsmentioning

confidence: 99%

“…More recent work in Xenopus has provided physiological evidence for this terminal location by showing that activation of nicotinic receptors increases sPSCs recorded in patch-clamped tectal cells (Titmus et al, 1999). These sPSCs are thought to reflect an increase in neurotransmitter release from glutamatergic retinal ganglion cells brought about by increased terminal calcium levels (Edwards and Cline, 1999).…”

Section: Nicotinic Receptor Location In the Optic Tectummentioning

confidence: 98%

“…Although inward current responses induced by nicotinic receptor agonists had been reported in the tectum (Titmus et al, 1999), these responses had not been characterized. Our finding that such currents can be recorded in 30% of cells makes it clear that nicotinic receptors, in addition to their presynaptic locations, have a substantial postsynaptic presence within the tectum.…”

Section: Nicotinic Receptor Location In the Optic Tectummentioning

confidence: 99%

“…Assessments of the effects of nicotinic receptor activation have focused on a facilitation of glutamate release from retinal ganglion cell terminals (Titmus et al, 1999;Kuras and Gutmaniene, 2001) while muscarinic receptors have been associated with tectal cell membranes following an enhancement of single unit recordings in response to ACh microiontophoresis (Fite and Wang, 1986). Using patchclamp techniques, we have examined the responses elicited in tectal neurons by nicotine and carbachol in order to begin to understand how nicotinic and muscarinic receptor activity, respectively, might modulate tectal activity patterns through presynaptic and postsynaptic means.…”

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confidence: 99%

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The effects of nicotinic and muscarinic receptor activation on patch-clamped cells in the optic tectum of rana pipiens

Debski

2003

Neuroscience

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Both nicotinic and muscarinic cholinergic receptors are present in the optic tectum. To begin to understand how the activation of these receptors affects visual activity patterns, we have determined the types of physiological responses induced by their activation. Using tectal brain slices from the leopard frog, we found that application of nicotine (100 μM) evoked long-lasting responses in 60% of patch-clamped tectal cells. Thirty percent of these responses consisted of an increase in spontaneous postsynaptic currents (sPSCs) and had both a glutamatergic and GABAergic component as determined by the use of 6-cyano-7-nitroquinoxaline-2,3-dione (50 μM) and bicuculline (25 μM), respectively. Remaining response types consisted of an inward membrane current (16%) and an increase in sPSCs combined with an inward membrane current (14%). All responses could be elicited in the presence of tetrodotoxin (0.5 μM). Muscarinic receptor-mediated responses, induced by carbachol (100 μM) application after nicotinic receptor desensitization, produced responses in 70% of tectal cells. In contrast to responses elicited by nicotine, carbachol-induced responses could be evoked multiple times without significant decrement. Responses consisted of either an outward current (57%), a decrease in sPSCs (5%) or an increase in sPSCs, with (almost 6%) or without (almost 3%) an outward current. The response elicited by carbachol was not predicted by the response of the cell to nicotine.Our results suggest that nicotinic receptors are found predominantly at presynaptic locations in the optic tectum while muscarinic receptors are most often present at postsynaptic sites. We conclude that both of these receptor types could substantially modulate visual activity by changing either the input to tectal neurons or the level of their response to that input. Keywords frog; retinotectal; acetylcholine; visual system; cholinergic; superior colliculus Acetylcholine (ACh) is present in many regions throughout the visual system appearing in the retina, superior colliculus, lateral geniculate nucleus, suprachiasmatic nuclei and the visual cortex (Groos et al., 1983;Sastry, 1985;Hohmann and Berger-Sweeney, 1998;Bickford et al., 2000). Contributed by both intrinsic and extrinsic sources (Sherman and Koch, 1986;Nobili and Sannita, 1997;Binns, 1999), cholinergic activity influences system function, plasticity and development (Greuel et al., 1988;Hohmann and Berger-Sweeney, 1998;Lauder and Schambra, 1999). Disturbances of this activity can result in such things as delayed neuronal development, changes in cytoarchitecture (Hohmann and Berger-Sweeney, 1998;Lauder and Schambra, 1999) and impaired ocular dominance shifts (Bear and Singer, 1986;Gordon et al., 1990). However, how ACh affects system activity and contributes to the mechanisms responsible for normal brain organization is not understood. The optic tectum of the frog provides an attractive model system for examining the ways in which cholinergic activity modulates visual system function and plastici...

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Section: Nicotinic Receptor Location In the Optic Tectumsupporting

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Section: Nicotinic Receptor Location In the Optic Tectummentioning

confidence: 98%

Section: Nicotinic Receptor Location In the Optic Tectummentioning

confidence: 99%

mentioning

confidence: 99%

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The effects of nicotinic and muscarinic receptor activation on patch-clamped cells in the optic tectum of rana pipiens

Debski

2003

Neuroscience

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Distribution and development of nicotinic acetylcholine receptor subtypes in the optic tectum ofRana pipiens

2000

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Acetylcholine allows the elicitation of visually evoked behaviors mediated by the frog optic tectum, but the mechanisms behind its effects are unknown. Although nicotinic acetylcholine receptors (nAChRs) exist in the tectum, their subtype has not been assessed. By using quantitative autoradiography, we examined the binding of [(3)H]cytisine and [(125)I]alpha-bungarotoxin in the laminated tectum. In mammalian systems, these radioligands bind with high affinity to alpha4 nAChR subunits and alpha7 nAChR subunits, respectively. [(3)H]Cytisine demonstrated high specific binding in adult frogs in retinorecipient layer 9, intermediate densities in layer 8, and low binding in layers 1-7 of the tectum. [(3)H]Cytisine binding was significantly higher in the tecta of adults than in those of tadpoles. Lesioning the optic nerve for 6 weeks decreased [(3)H]cytisine binding in layers 8/9 by 70+/-1%, whereas 6-month lesions decreased binding by 76+/-3%. Specific binding of [(125)I]alpha-bungarotoxin in adults was present only at intermediate levels in tectal layers 8 and 9, and undetectable in the deeper tectal layers. However, the nucleus isthmi, a midbrain structure reciprocally connected to the tectum, exhibited high levels of binding. There were no significant differences in tectal [(125)I]alpha-bungarotoxin binding between tadpoles and adults. Six-week lesions of the optic nerve decreased tectal [(125)I]alpha-bungarotoxin binding by 33+/-10%, but 6-month lesions had no effect. The pharmacokinetic characteristics of [(3)H]cytisine and [(125)I]alpha-bungarotoxin binding in the frog brain were similar to those demonstrated in several mammalian species. These results indicate that [(3)H]cytisine and [(125)I]alpha-bungarotoxin identify distinct nAChR subtypes in the tectum that likely contain non-alpha7 and alpha7 subunits, respectively. The majority of non-alpha7 receptors are likely associated with retinal ganglion cell terminals, whereas alpha7-containing receptors appear to have a different localization.

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Time‐lapse in vivo imaging of the morphological development of Xenopus optic tectal interneurons

Cline

2003

J of Comparative Neurology

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Excitatory and inhibitory interneurons play a key role in the establishment of neuronal responses and circuit properties in the brain. Despite their importance in brain function, the structural development of interneurons has not been well studied. We used in vivo time-lapse imaging in intact anesthetized Xenopus tadpoles to determine the morphological events underlying the development of interneuron dendritic arbor structure. Single optic tectal neurons were labeled with DiI and imaged at daily intervals over 4 days in intact albino Xenopus tadpoles. The same neurons were also imaged at shorter intervals to determine the dynamic rearrangements in arbor branches that accompany large-scale arbor growth. Tectal interneurons, like projection neurons, develop from neuroepithelial cells located near the ventricular layer. They elaborate complex dendritic arbors over a period of 2 days. Short-interval time-lapse images reveal that tectal interneuron arbors have rapid rates of branch additions and retractions. We identified four patterns of interneuron arbor development, based on the cell morphology and types of structural rearrangements that occur over the development of the neuronal arbor. A surprising feature of interneuronal development is the large extent of structural rearrangements: many interneurons extend transient processes so that the neuronal structure is dramatically different from one day to the next. Because the majority of synaptic contacts are formed on dendrites, the structural changes we observed in interneuronal dendritic arbors suggest that optic tectal circuits are extremely plastic during early stages of development.

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Effects of choline and other nicotinic agonists on the tectum of juvenile and adult Xenopus frogs: a patch-clamp study

Cited by 41 publications

References 66 publications

The effects of nicotinic and muscarinic receptor activation on patch-clamped cells in the optic tectum of rana pipiens

The effects of nicotinic and muscarinic receptor activation on patch-clamped cells in the optic tectum of rana pipiens

Distribution and development of nicotinic acetylcholine receptor subtypes in the optic tectum ofRana pipiens

Time‐lapse in vivo imaging of the morphological development of Xenopus optic tectal interneurons

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