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Secretagogin expression delineates functionally-specialized populations of striatal parvalbumin-containing interneurons

View Article: PubMed Central - PubMed

ABSTRACT

Corticostriatal afferents can engage parvalbumin-expressing (PV+) interneurons to rapidly curtail the activity of striatal projection neurons (SPNs), thus shaping striatal output. Schemes of basal ganglia circuit dynamics generally consider striatal PV+ interneurons to be homogenous, despite considerable heterogeneity in both form and function. We demonstrate that the selective co-expression of another calcium-binding protein, secretagogin (Scgn), separates PV+ interneurons in rat and primate striatum into two topographically-, physiologically- and structurally-distinct cell populations. In rats, these two interneuron populations differed in their firing rates, patterns and relationships with cortical oscillations in vivo. Moreover, the axons of identified PV+/Scgn+ interneurons preferentially targeted the somata of SPNs of the so-called ‘direct pathway’, whereas PV+/Scgn- interneurons preferentially targeted ‘indirect pathway’ SPNs. These two populations of interneurons could therefore provide a substrate through which either of the striatal output pathways can be rapidly and selectively inhibited to subsequently mediate the expression of behavioral routines.

Doi:: http://dx.doi.org/10.7554/eLife.16088.001

No MeSH data available.


Unsupervised hierarchical clustering of electrophysiological parameters segregate PV+/Scgn+ interneurons from established striatal interneuron types.(A) Scatter plots showing the values of 6 electrophysiological parameters used in the cluster analysis of juxtacellularly-labelled ChAT+ (red), GABAergic NOS+/NPY+ (black circles) and PV+ (dark blue) interneurons recorded during SWA (Ai) and cortical activation (Aii). See Materials and ethods for definitions of each parameter. Each variable separates two or more of the interneuron groups. (B) Dendrogram derived from 7D-cluster analysis using Ward’s method with a squared Euclidian distance measure to classify 65 striatal interneurons recorded during SWA using the parameters in Ai and one other (ECoG gamma vector length). The x-axis represents individual cells (ChAT+ in red, NOS+/NPY+ in black, PV+/Scgn- in green, PV+/Scgn+ in light blue), the y-axis represents average linkage distance between neurons, where longer distance represents greater dissimilarity. The dotted redline represents the threshold for separating clusters, which are highlighted by grey boxes, together with the p-value for this threshold. Five clusters are formed, two made up mostly of ChAT+ interneurons and the other three of different types of GABAergic interneurons. (C, D) The same analysis run only on the GABAergic interneurons (C) and only on PV+ interneurons (D). (C) The three significant clusters correspond to the three different molecular marker combinations with >70% accuracy. (D) Upper, in the 7D space, the two significant clusters for PV+ interneurons are roughly segregated according to Scgn expression. Lower, 4D-cluster analysis using only parameters related to population locking. The two significant clusters are almost completely predicted by Scgn expression. (E) Dendrogram of 6D cluster analysis of 48 interneurons recorded during cortical activation using the parameters in Aii. 4 clusters are significantly segregated, each with a clear majority of cells with a single molecular identity. (F) Analysis of only GABAergic interneurons leads to 3 significant clusters highly correlated with the 3 interneuron types. (G) Analysis of only PV+ interneurons led to 3 significant clusters, 2 of which were predominantly comprised of PV+/Scgn- interneurons. The third cluster, which had the widest segregation, was comprised only of PV+/Scgn+ interneurons.DOI:http://dx.doi.org/10.7554/eLife.16088.01910.7554/eLife.16088.020Figure 10—source data 1.Source data for Figure 10.DOI:http://dx.doi.org/10.7554/eLife.16088.020
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fig10: Unsupervised hierarchical clustering of electrophysiological parameters segregate PV+/Scgn+ interneurons from established striatal interneuron types.(A) Scatter plots showing the values of 6 electrophysiological parameters used in the cluster analysis of juxtacellularly-labelled ChAT+ (red), GABAergic NOS+/NPY+ (black circles) and PV+ (dark blue) interneurons recorded during SWA (Ai) and cortical activation (Aii). See Materials and ethods for definitions of each parameter. Each variable separates two or more of the interneuron groups. (B) Dendrogram derived from 7D-cluster analysis using Ward’s method with a squared Euclidian distance measure to classify 65 striatal interneurons recorded during SWA using the parameters in Ai and one other (ECoG gamma vector length). The x-axis represents individual cells (ChAT+ in red, NOS+/NPY+ in black, PV+/Scgn- in green, PV+/Scgn+ in light blue), the y-axis represents average linkage distance between neurons, where longer distance represents greater dissimilarity. The dotted redline represents the threshold for separating clusters, which are highlighted by grey boxes, together with the p-value for this threshold. Five clusters are formed, two made up mostly of ChAT+ interneurons and the other three of different types of GABAergic interneurons. (C, D) The same analysis run only on the GABAergic interneurons (C) and only on PV+ interneurons (D). (C) The three significant clusters correspond to the three different molecular marker combinations with >70% accuracy. (D) Upper, in the 7D space, the two significant clusters for PV+ interneurons are roughly segregated according to Scgn expression. Lower, 4D-cluster analysis using only parameters related to population locking. The two significant clusters are almost completely predicted by Scgn expression. (E) Dendrogram of 6D cluster analysis of 48 interneurons recorded during cortical activation using the parameters in Aii. 4 clusters are significantly segregated, each with a clear majority of cells with a single molecular identity. (F) Analysis of only GABAergic interneurons leads to 3 significant clusters highly correlated with the 3 interneuron types. (G) Analysis of only PV+ interneurons led to 3 significant clusters, 2 of which were predominantly comprised of PV+/Scgn- interneurons. The third cluster, which had the widest segregation, was comprised only of PV+/Scgn+ interneurons.DOI:http://dx.doi.org/10.7554/eLife.16088.01910.7554/eLife.16088.020Figure 10—source data 1.Source data for Figure 10.DOI:http://dx.doi.org/10.7554/eLife.16088.020

Mentions: Eighty three percent of the cholinergic interneurons and all of the NOS+/NPY+ interneurons used here have been reported in previous papers (Sharott et al., 2012; Doig et al., 2014). Because the firing rates and patterns of striatal interneurons varies considerably between SWA and cortical activation (Sharott et al., 2012), we performed separate cluster analyses for parameters recorded in each brain state. For activity during SWA, we analyzed a total of 65 interneurons; 36 ChAT+, 12 NOS+/NPY+ and 17 PV+ interneurons. Three measures of interneuron firing regularity/pattern (Log ISI 10, CV ISI and CV2 ratio; see Materials and methods) and 4 measures of interneuron locking to population oscillations in the ECoG (LFP peak, SWA Vec., Spin. Vec and Gam. Vec; see Materials and methods) were used for clustering (Figure 10Ai, Figure 10—source data 1). When these 7 parameters were analyzed across all interneuron populations, 5 significant clusters emerged (Figure 10B). After assignment of molecular identities, it was evident that two of these clusters were predominantly composed of cholinergic interneurons (Figure 10B). The three remaining clusters were composed of a clear majority of PV+/Scgn-, PV+/Scgn+ or NOS+/NPY+ interneurons. The PV+/Scgn- and PV+/Scgn+ interneurons were therefore segregated to a similar degree as the ChAT+ and NOS+/NPY+ interneurons. When the ChAT+ interneurons were removed and the analysis repeated, the GABAergic interneurons segregated into 3 significant clusters with a slightly improved clustering of the NOS+/NPY+ interneurons and a similar separation of the two PV+ populations to the larger analysis (Figure 10C). With the removal of NOS+/NPY+ interneurons, the segregation of PV+/Scgn- and PV+/Scgn- interneurons was largely maintained (Figure 10D). When only the 4 measures of interneuron locking were used in the analysis, PV+ interneurons were segregated into two significant clusters with >85% correlation with Scgn expression (Figure 10D). This could reflect the relatively large influence of cortical oscillations on the firing patterns of striatal GABAergic interneurons in this brain state (Sharott et al, 2012).10.7554/eLife.16088.019Figure 10.Unsupervised hierarchical clustering of electrophysiological parameters segregate PV+/Scgn+ interneurons from established striatal interneuron types.


Secretagogin expression delineates functionally-specialized populations of striatal parvalbumin-containing interneurons
Unsupervised hierarchical clustering of electrophysiological parameters segregate PV+/Scgn+ interneurons from established striatal interneuron types.(A) Scatter plots showing the values of 6 electrophysiological parameters used in the cluster analysis of juxtacellularly-labelled ChAT+ (red), GABAergic NOS+/NPY+ (black circles) and PV+ (dark blue) interneurons recorded during SWA (Ai) and cortical activation (Aii). See Materials and ethods for definitions of each parameter. Each variable separates two or more of the interneuron groups. (B) Dendrogram derived from 7D-cluster analysis using Ward’s method with a squared Euclidian distance measure to classify 65 striatal interneurons recorded during SWA using the parameters in Ai and one other (ECoG gamma vector length). The x-axis represents individual cells (ChAT+ in red, NOS+/NPY+ in black, PV+/Scgn- in green, PV+/Scgn+ in light blue), the y-axis represents average linkage distance between neurons, where longer distance represents greater dissimilarity. The dotted redline represents the threshold for separating clusters, which are highlighted by grey boxes, together with the p-value for this threshold. Five clusters are formed, two made up mostly of ChAT+ interneurons and the other three of different types of GABAergic interneurons. (C, D) The same analysis run only on the GABAergic interneurons (C) and only on PV+ interneurons (D). (C) The three significant clusters correspond to the three different molecular marker combinations with >70% accuracy. (D) Upper, in the 7D space, the two significant clusters for PV+ interneurons are roughly segregated according to Scgn expression. Lower, 4D-cluster analysis using only parameters related to population locking. The two significant clusters are almost completely predicted by Scgn expression. (E) Dendrogram of 6D cluster analysis of 48 interneurons recorded during cortical activation using the parameters in Aii. 4 clusters are significantly segregated, each with a clear majority of cells with a single molecular identity. (F) Analysis of only GABAergic interneurons leads to 3 significant clusters highly correlated with the 3 interneuron types. (G) Analysis of only PV+ interneurons led to 3 significant clusters, 2 of which were predominantly comprised of PV+/Scgn- interneurons. The third cluster, which had the widest segregation, was comprised only of PV+/Scgn+ interneurons.DOI:http://dx.doi.org/10.7554/eLife.16088.01910.7554/eLife.16088.020Figure 10—source data 1.Source data for Figure 10.DOI:http://dx.doi.org/10.7554/eLife.16088.020
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fig10: Unsupervised hierarchical clustering of electrophysiological parameters segregate PV+/Scgn+ interneurons from established striatal interneuron types.(A) Scatter plots showing the values of 6 electrophysiological parameters used in the cluster analysis of juxtacellularly-labelled ChAT+ (red), GABAergic NOS+/NPY+ (black circles) and PV+ (dark blue) interneurons recorded during SWA (Ai) and cortical activation (Aii). See Materials and ethods for definitions of each parameter. Each variable separates two or more of the interneuron groups. (B) Dendrogram derived from 7D-cluster analysis using Ward’s method with a squared Euclidian distance measure to classify 65 striatal interneurons recorded during SWA using the parameters in Ai and one other (ECoG gamma vector length). The x-axis represents individual cells (ChAT+ in red, NOS+/NPY+ in black, PV+/Scgn- in green, PV+/Scgn+ in light blue), the y-axis represents average linkage distance between neurons, where longer distance represents greater dissimilarity. The dotted redline represents the threshold for separating clusters, which are highlighted by grey boxes, together with the p-value for this threshold. Five clusters are formed, two made up mostly of ChAT+ interneurons and the other three of different types of GABAergic interneurons. (C, D) The same analysis run only on the GABAergic interneurons (C) and only on PV+ interneurons (D). (C) The three significant clusters correspond to the three different molecular marker combinations with >70% accuracy. (D) Upper, in the 7D space, the two significant clusters for PV+ interneurons are roughly segregated according to Scgn expression. Lower, 4D-cluster analysis using only parameters related to population locking. The two significant clusters are almost completely predicted by Scgn expression. (E) Dendrogram of 6D cluster analysis of 48 interneurons recorded during cortical activation using the parameters in Aii. 4 clusters are significantly segregated, each with a clear majority of cells with a single molecular identity. (F) Analysis of only GABAergic interneurons leads to 3 significant clusters highly correlated with the 3 interneuron types. (G) Analysis of only PV+ interneurons led to 3 significant clusters, 2 of which were predominantly comprised of PV+/Scgn- interneurons. The third cluster, which had the widest segregation, was comprised only of PV+/Scgn+ interneurons.DOI:http://dx.doi.org/10.7554/eLife.16088.01910.7554/eLife.16088.020Figure 10—source data 1.Source data for Figure 10.DOI:http://dx.doi.org/10.7554/eLife.16088.020
Mentions: Eighty three percent of the cholinergic interneurons and all of the NOS+/NPY+ interneurons used here have been reported in previous papers (Sharott et al., 2012; Doig et al., 2014). Because the firing rates and patterns of striatal interneurons varies considerably between SWA and cortical activation (Sharott et al., 2012), we performed separate cluster analyses for parameters recorded in each brain state. For activity during SWA, we analyzed a total of 65 interneurons; 36 ChAT+, 12 NOS+/NPY+ and 17 PV+ interneurons. Three measures of interneuron firing regularity/pattern (Log ISI 10, CV ISI and CV2 ratio; see Materials and methods) and 4 measures of interneuron locking to population oscillations in the ECoG (LFP peak, SWA Vec., Spin. Vec and Gam. Vec; see Materials and methods) were used for clustering (Figure 10Ai, Figure 10—source data 1). When these 7 parameters were analyzed across all interneuron populations, 5 significant clusters emerged (Figure 10B). After assignment of molecular identities, it was evident that two of these clusters were predominantly composed of cholinergic interneurons (Figure 10B). The three remaining clusters were composed of a clear majority of PV+/Scgn-, PV+/Scgn+ or NOS+/NPY+ interneurons. The PV+/Scgn- and PV+/Scgn+ interneurons were therefore segregated to a similar degree as the ChAT+ and NOS+/NPY+ interneurons. When the ChAT+ interneurons were removed and the analysis repeated, the GABAergic interneurons segregated into 3 significant clusters with a slightly improved clustering of the NOS+/NPY+ interneurons and a similar separation of the two PV+ populations to the larger analysis (Figure 10C). With the removal of NOS+/NPY+ interneurons, the segregation of PV+/Scgn- and PV+/Scgn- interneurons was largely maintained (Figure 10D). When only the 4 measures of interneuron locking were used in the analysis, PV+ interneurons were segregated into two significant clusters with >85% correlation with Scgn expression (Figure 10D). This could reflect the relatively large influence of cortical oscillations on the firing patterns of striatal GABAergic interneurons in this brain state (Sharott et al, 2012).10.7554/eLife.16088.019Figure 10.Unsupervised hierarchical clustering of electrophysiological parameters segregate PV+/Scgn+ interneurons from established striatal interneuron types.

View Article: PubMed Central - PubMed

ABSTRACT

Corticostriatal afferents can engage parvalbumin-expressing (PV+) interneurons to rapidly curtail the activity of striatal projection neurons (SPNs), thus shaping striatal output. Schemes of basal ganglia circuit dynamics generally consider striatal PV+ interneurons to be homogenous, despite considerable heterogeneity in both form and function. We demonstrate that the selective co-expression of another calcium-binding protein, secretagogin (Scgn), separates PV+ interneurons in rat and primate striatum into two topographically-, physiologically- and structurally-distinct cell populations. In rats, these two interneuron populations differed in their firing rates, patterns and relationships with cortical oscillations in vivo. Moreover, the axons of identified PV+/Scgn+ interneurons preferentially targeted the somata of SPNs of the so-called ‘direct pathway’, whereas PV+/Scgn- interneurons preferentially targeted ‘indirect pathway’ SPNs. These two populations of interneurons could therefore provide a substrate through which either of the striatal output pathways can be rapidly and selectively inhibited to subsequently mediate the expression of behavioral routines.

Doi:: http://dx.doi.org/10.7554/eLife.16088.001

No MeSH data available.