Fig 2: PV+/Scgn+ and PV+/Scgn- interneurons have different biases in their distributions in the caudate and putamen of macaque monkey.(Ai, Aii) Confocal micrographs of the macaque striatum showing PV-expressing interneurons that co-expressed (Ai) and did not co-express (Aii) Scgn (arrow). (B) Typical distributions of PV+/Scgn- interneurons (left) and PV+/Scgn+ interneurons (right) across 7 coronal planes of macaque caudate and putamen, with each dot representing a single neuron. (C) Mean densities of all PV+ interneurons across the entirety of the caudate nucleus (Ci) and the putamen (Cii), including those populations that co-express Scgn (blue) and do not express Scgn (green). In the macaque caudate-putamen, PV+/Scgn+ neurons represent nearly three quarters of all PV-expressing neurons. Dots and squares indicate the values for individual animals. (D) Densities of PV+/Scgn+ interneurons (blue) and PV+/Scgn- interneurons (green) along the rostro-caudal axis of the caudate (Di) and the putamen (Dii). Note that the PV+/Scgn+ population in the macaque increases in density towards the caudal planes of the caudate and the putamen. (E) Medio-lateral distribution of PV+/Scgn+ and PV+/Scgn- interneurons along 7 coronal planes of the caudate nucleus (Ei) and the putamen (Eii). The presence of the asterisk (*) indicates a distribution that is significantly biased in one direction along the specified axis. Squares (□) indicate a significant difference in the distribution of the two PV+ interneuron populations along the specified axis within a given coronal plane. Data are means of the position of all neurons counted ± SEMs.DOI: http://dx.doi.org/10.7554/eLife.16088.00710.7554/eLife.16088.008Figure 3—source data 1.Source data for Figures 3B–E.DOI: http://dx.doi.org/10.7554/eLife.16088.008

Fig 3: CR+/Scgn+ interneurons can be distinguished from CR+/Scgn− interneurons on the basis of their mean somatic diameters. (a) Frequency histogram showing the trimodal distribution of somatic diameters for CR+ interneurons in the dorsal striatum of three rats. (b) Frequency histogram of the same population as in (a), but now showing the distribution of somatic diameters of CR+/Scgn+ interneurons (cyan bars) and CR+/Scgn− interneurons (green bars). (c) CR+/Scgn+ interneurons were found to possess significantly smaller‐sized somata compared to CR+/Scgn− interneurons (Mann‐Whitney U test, p = 1.68 × 10−189). Data in plot (c) are the medians, the interquartile ranges (box), and extremes of the range (whiskers show the lowest and highest points within 1.5× the interquartile range, approximately 99% of the data for a normal distribution)

Fig 4: PV+/Scgn- and PV+/Scgn+ striatal interneurons selectively target the somata of SPNs in the direct or indirect pathway.(Ai) Confocal fluorescent micrograph stack of a neurobiotin (NB)-labeled axon of a PV+/Scgn- interneuron (green) targeting a SPN revealed with DARRP-32 (purple). The interneuron axon forms 4 appositions (numbered white arrows) with the SPN soma. (Aii) The SPN expresses preproenkephalin (PPE, white), indicating it is in the indirect pathway (iSPN). (Aiii, Aiv) Single-plane confocal micrographs verifying that each of the 4 boutons is closely apposed to the SPN soma. (Bi) Confocal fluorescent micrograph stack of the NB-labeled axon of a PV+/Scgn+ interneuron (blue) traversing close to two SPNs. The axon forms 3 appositions (white arrows) with the SPN soma on the left, and appears to form a single apposition (red arrow) with the SPN on right. (Bii) The right SPN expresses PPE (iSPN), while the left SPN does not, indicating it is in the direct pathway (dSPN). (Biii, Biv), Single-plane confocal micrographs verifying that boutons 1–3 are apposed to the soma of the dSPN, while bouton 4 is not directly apposed to the iSPN. (C) Quantitative analyses of the NB-labeled axonal boutons of PV+/Scgn- and PV+/Scgn+ interneurons revealed that the axons of PV+/Scgn- interneurons were more likely to be opposed to the somata of SPNs. (D) Histogram of the frequency of different numbers of appositions formed with an individual SPN soma for both types of interneuron. (E) The axons of PV+/Scgn- interneurons were more likely than the axons of PV+/Scgn+ interneurons to target the somata of PPE+ SPNs of the indirect pathway.(A,B, scale bars are 20 µm.)DOI: http://dx.doi.org/10.7554/eLife.16088.01510.7554/eLife.16088.016Figure 8—source data 1.Source data for Figure 8C,D,E.DOI: http://dx.doi.org/10.7554/eLife.16088.016

Fig 5: Spontaneous activity of identified CR+/Scgn−/Lhx7− striatal interneurons in the rat dorsal striatum. (a–f) Juxtacellularly labeled CR‐expressing interneurons (a, d), identified by their colocalization of fluorescent labeling for Neurobiotin (NB). Both interneurons tested negative for the expression of both Scgn and Lhx7. Scale bars = 20 µm. (b, e) Spontaneous action potential discharges (unit activity) of the same individual CR+ interneurons during cortical slow‐wave activity, as recorded in the frontal electrocorticogram (ECoG). (c, f) Firing of the same interneurons during spontaneous cortical activation. Scale bars for recordings represent 0.5 mV for the unit activity and 1 mV for the ECoG. (g) The mean action potential waveforms of the four CR+/Scgn−/Lhx7− interneurons recorded and identified in this study. (h) The mean firing rates of CR+/Scgn−/Lhx7− interneurons during both cortical slow‐wave activity and cortical activation. (i, j) ISI histograms of each recorded CR+ interneuron during cortical SWA (i) and cortical activation (j). (g–j) Note that the different colored lines represent one of the four CR+/Scgn−/Lhx7− interneurons