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Coexistence of glutamatergic spine synapses and shaft synapses in substantia nigra dopamine neurons.

Jang M, Um KB, Jang J, Kim HJ, Cho H, Chung S, Park MK - Sci Rep (2015)

Bottom Line: Using local two-photon glutamate uncaging techniques, we confirmed that shaft synapses and spine synapses had both AMPA and NMDA receptors, but the AMPA/NMDA current ratios differed.Therefore, we provide the first evidence that the midbrain dopamine neurons have two morphologically and functionally distinct types of glutamatergic synapses, spine synapses and shaft synapses, on the same dendrite.This peculiar organization could be a new basis for unraveling many physiological and pathological functions of the midbrain dopamine neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Sungkyunkwan University School of Medicine 300 Chunchun-dong, Jangan-ku, Suwon, 440-746, Korea.

ABSTRACT
Dopamine neurons of the substantia nigra have long been believed to have multiple aspiny dendrites which receive many glutamatergic synaptic inputs from several regions of the brain. But, here, using high-resolution two-photon confocal microscopy in the mouse brain slices, we found a substantial number of common dendritic spines in the nigral dopamine neurons including thin, mushroom, and stubby types of spines. However, the number of dendritic spines of the dopamine neurons was approximately five times lower than that of CA1 pyramidal neurons. Immunostaining and morphological analysis revealed that glutamatergic shaft synapses were present two times more than spine synapses. Using local two-photon glutamate uncaging techniques, we confirmed that shaft synapses and spine synapses had both AMPA and NMDA receptors, but the AMPA/NMDA current ratios differed. The evoked postsynaptic potentials of spine synapses showed lower amplitudes but longer half-widths than those of shaft synapses. Therefore, we provide the first evidence that the midbrain dopamine neurons have two morphologically and functionally distinct types of glutamatergic synapses, spine synapses and shaft synapses, on the same dendrite. This peculiar organization could be a new basis for unraveling many physiological and pathological functions of the midbrain dopamine neurons.

No MeSH data available.


Related in: MedlinePlus

Functional identification of glutamatergic spine synapses in the SNc dopamine neurons.Single uEPSCs from a single dendritic spine were measured using two-photon glutamate uncaging. (a) Reconstructed image of a recorded neuron filled with Alexa Fluor 594 with two recording sites. (b) Top, high-magnification image of the target dendritic segment indicated by the red box in a. Yellow dots indicate uncaging sites. Bottom, representative traces of uncaging-evoked EPSCs. (c) Summary of recordings from 4 spines in 4 cells. (d) Left, illustration of the target dendrite from the red box indicated in a. Red dots indicate the uncaging locations with distance from the dendritic spine head. Right, representative traces of uncaging-evoked EPSCs. uEPSCs decreased as the uncaging spot was moved away from the spine head. (e) The first point corresponds to data obtained by uncaging on the spine head. Each subsequent point was normalized to this point (n = 5). (f) Monochrome image magnifying the target dendritic segment indicated by the blue box in a. (g) Representative traces of uncaging-evoked EPSCs in the absence (black) and presence (red) of CPP. (h) Summary of the widths of uEPSCs. AMPAR EPSCs were recorded at −60 mV in the absence (black, n = 5) or presence (red, n = 5) of CPP and at +40 mV in the presence of CPP (red, n = 5). The amplitudes of the NMDAR EPSCs were measured at 14 ms after the onset (blue dotted line), when the AMPAR EPSCs had returned to baseline.
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f4: Functional identification of glutamatergic spine synapses in the SNc dopamine neurons.Single uEPSCs from a single dendritic spine were measured using two-photon glutamate uncaging. (a) Reconstructed image of a recorded neuron filled with Alexa Fluor 594 with two recording sites. (b) Top, high-magnification image of the target dendritic segment indicated by the red box in a. Yellow dots indicate uncaging sites. Bottom, representative traces of uncaging-evoked EPSCs. (c) Summary of recordings from 4 spines in 4 cells. (d) Left, illustration of the target dendrite from the red box indicated in a. Red dots indicate the uncaging locations with distance from the dendritic spine head. Right, representative traces of uncaging-evoked EPSCs. uEPSCs decreased as the uncaging spot was moved away from the spine head. (e) The first point corresponds to data obtained by uncaging on the spine head. Each subsequent point was normalized to this point (n = 5). (f) Monochrome image magnifying the target dendritic segment indicated by the blue box in a. (g) Representative traces of uncaging-evoked EPSCs in the absence (black) and presence (red) of CPP. (h) Summary of the widths of uEPSCs. AMPAR EPSCs were recorded at −60 mV in the absence (black, n = 5) or presence (red, n = 5) of CPP and at +40 mV in the presence of CPP (red, n = 5). The amplitudes of the NMDAR EPSCs were measured at 14 ms after the onset (blue dotted line), when the AMPAR EPSCs had returned to baseline.

Mentions: Next we asked whether the dendritic spines present on the dendrites of the dopamine neurons can function as a real glutamatergic synapse. We addressed this question using whole-cell patch-clamp recordings combined with two-photon glutamate uncaging techniques in live midbrain slices. Dopamine neurons were filled with the red-fluorescence dye Alexa Fluor 594 (30 μM) through the patch pipette to visualize the dendritic shafts and spines. To detect very small current changes from a single synapse, the proximal dendritic regions within 100 μm from the soma were intensively investigated (Figs 4, 5, 6, 7).


Coexistence of glutamatergic spine synapses and shaft synapses in substantia nigra dopamine neurons.

Jang M, Um KB, Jang J, Kim HJ, Cho H, Chung S, Park MK - Sci Rep (2015)

Functional identification of glutamatergic spine synapses in the SNc dopamine neurons.Single uEPSCs from a single dendritic spine were measured using two-photon glutamate uncaging. (a) Reconstructed image of a recorded neuron filled with Alexa Fluor 594 with two recording sites. (b) Top, high-magnification image of the target dendritic segment indicated by the red box in a. Yellow dots indicate uncaging sites. Bottom, representative traces of uncaging-evoked EPSCs. (c) Summary of recordings from 4 spines in 4 cells. (d) Left, illustration of the target dendrite from the red box indicated in a. Red dots indicate the uncaging locations with distance from the dendritic spine head. Right, representative traces of uncaging-evoked EPSCs. uEPSCs decreased as the uncaging spot was moved away from the spine head. (e) The first point corresponds to data obtained by uncaging on the spine head. Each subsequent point was normalized to this point (n = 5). (f) Monochrome image magnifying the target dendritic segment indicated by the blue box in a. (g) Representative traces of uncaging-evoked EPSCs in the absence (black) and presence (red) of CPP. (h) Summary of the widths of uEPSCs. AMPAR EPSCs were recorded at −60 mV in the absence (black, n = 5) or presence (red, n = 5) of CPP and at +40 mV in the presence of CPP (red, n = 5). The amplitudes of the NMDAR EPSCs were measured at 14 ms after the onset (blue dotted line), when the AMPAR EPSCs had returned to baseline.
© Copyright Policy - open-access
Related In: Results  -  Collection

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f4: Functional identification of glutamatergic spine synapses in the SNc dopamine neurons.Single uEPSCs from a single dendritic spine were measured using two-photon glutamate uncaging. (a) Reconstructed image of a recorded neuron filled with Alexa Fluor 594 with two recording sites. (b) Top, high-magnification image of the target dendritic segment indicated by the red box in a. Yellow dots indicate uncaging sites. Bottom, representative traces of uncaging-evoked EPSCs. (c) Summary of recordings from 4 spines in 4 cells. (d) Left, illustration of the target dendrite from the red box indicated in a. Red dots indicate the uncaging locations with distance from the dendritic spine head. Right, representative traces of uncaging-evoked EPSCs. uEPSCs decreased as the uncaging spot was moved away from the spine head. (e) The first point corresponds to data obtained by uncaging on the spine head. Each subsequent point was normalized to this point (n = 5). (f) Monochrome image magnifying the target dendritic segment indicated by the blue box in a. (g) Representative traces of uncaging-evoked EPSCs in the absence (black) and presence (red) of CPP. (h) Summary of the widths of uEPSCs. AMPAR EPSCs were recorded at −60 mV in the absence (black, n = 5) or presence (red, n = 5) of CPP and at +40 mV in the presence of CPP (red, n = 5). The amplitudes of the NMDAR EPSCs were measured at 14 ms after the onset (blue dotted line), when the AMPAR EPSCs had returned to baseline.
Mentions: Next we asked whether the dendritic spines present on the dendrites of the dopamine neurons can function as a real glutamatergic synapse. We addressed this question using whole-cell patch-clamp recordings combined with two-photon glutamate uncaging techniques in live midbrain slices. Dopamine neurons were filled with the red-fluorescence dye Alexa Fluor 594 (30 μM) through the patch pipette to visualize the dendritic shafts and spines. To detect very small current changes from a single synapse, the proximal dendritic regions within 100 μm from the soma were intensively investigated (Figs 4, 5, 6, 7).

Bottom Line: Using local two-photon glutamate uncaging techniques, we confirmed that shaft synapses and spine synapses had both AMPA and NMDA receptors, but the AMPA/NMDA current ratios differed.Therefore, we provide the first evidence that the midbrain dopamine neurons have two morphologically and functionally distinct types of glutamatergic synapses, spine synapses and shaft synapses, on the same dendrite.This peculiar organization could be a new basis for unraveling many physiological and pathological functions of the midbrain dopamine neurons.

View Article: PubMed Central - PubMed

Affiliation: Department of Physiology, Sungkyunkwan University School of Medicine 300 Chunchun-dong, Jangan-ku, Suwon, 440-746, Korea.

ABSTRACT
Dopamine neurons of the substantia nigra have long been believed to have multiple aspiny dendrites which receive many glutamatergic synaptic inputs from several regions of the brain. But, here, using high-resolution two-photon confocal microscopy in the mouse brain slices, we found a substantial number of common dendritic spines in the nigral dopamine neurons including thin, mushroom, and stubby types of spines. However, the number of dendritic spines of the dopamine neurons was approximately five times lower than that of CA1 pyramidal neurons. Immunostaining and morphological analysis revealed that glutamatergic shaft synapses were present two times more than spine synapses. Using local two-photon glutamate uncaging techniques, we confirmed that shaft synapses and spine synapses had both AMPA and NMDA receptors, but the AMPA/NMDA current ratios differed. The evoked postsynaptic potentials of spine synapses showed lower amplitudes but longer half-widths than those of shaft synapses. Therefore, we provide the first evidence that the midbrain dopamine neurons have two morphologically and functionally distinct types of glutamatergic synapses, spine synapses and shaft synapses, on the same dendrite. This peculiar organization could be a new basis for unraveling many physiological and pathological functions of the midbrain dopamine neurons.

No MeSH data available.


Related in: MedlinePlus