These results show that CB+ dendrite-targeting cells represent a specific cell type, whose firing is synchronized with CA1 θ (Figure 5A). We discovered a GABAergic cell type that projects to the amygdalo-striatal transition area (AStria, hence its name), as well as innervating the BLA (Figures 4C and S7B). The firing of most AStria-projecting cells (mean frequency 4.01 Hz, range 3.4–6.0 Hz, n = 4; Table 1) was related to dCA1 θ (n = 3/4, mean r = 0.12). Two of these cells preferentially fired before the peak (Figure 4A)
PFI-2 supplier and one fired most during the descending phase of the θ rhythm (Figures 5B and S2; Table 1). As a result, this cell population was not statistically phase-locked to hippocampal θ (R′ = 0.86, R0.05,3 = 1.095, Moore test). The firing of AStria-projecting neurons was not modulated with dCA1 γ oscillations (p > 0.04, Rayleigh test, n = 4; Figure S3; Table S3). In contrast to the previous three cell types, AStria-projecting cells were robustly inhibited by noxious stimuli. Hindpaw pinches suppressed the firing of 3/4 cells tested (Figure 4B; mean latency 2,133 ms, peak 2,200 ms; ranges, 1,000–3,800 ms for peak and latency; Table 2; Figure S4). In two cells, this inhibition persisted for several seconds after the pinch offset (Figure 5D). Electrical footshocks
also elicited strong inhibitory responses selleck inhibitor in AStria-projecting cells (−85% of baseline, latency 33 ms, peak 380 ms, n = 3; ranges: 75%–100%, 20–60 ms, 20–740 ms, respectively; Figures S5 and 5C). The axon projecting to the AStria innervated somata and dendrites of DARPP-32+ cells, likely medium-sized spiny neurons (Anderson and Reiner, 1991), which also expressed CaMKIIα (Figures 4D, 4E, and S6D). Most of the axons were distributed in the BLA, where they made dense ramifications (Figures 4C and S7B). Studied with light microscopy, a proportion of the large axon varicosities made multiple perisomatic contacts with CaMKIIα+ BLA principal neurons; the others
possibly contacted small dendrites (Figure 4G). Electron microscopic analysis confirmed that postsynaptic targets in the lateral nucleus were dendrites (Figure 4F) and Idoxuridine somata (35% and 65%, respectively, n = 40 synapses, 2 cells; Table S1). Of these, 35% were confirmed CaMKIIα+ neurons (Figure 4F, Table S1). Dendrites targeted by AStria-projecting neurons were smaller than those postsynaptic to PV+ basket cells but larger than those targeted by CB+ dendrite-targeting cells (diameter 0.79 ± 0.06 μm, p < 0.05; Figure S6E). All AStria-projecting neurons expressed PV (Figure 4H), and half also expressed CB. GABAAR-α1 was moderately enriched in the plasma membrane of one cell but was never strongly expressed, in contrast to PV+ basket cells (Table S2). Dendrites were multipolar and branched profusely. They were short, smooth, and very tortuous (Figures 4C and S7B).