Physiological and morphological characterization of parvalbumin‐containing interneurons of the rat basolateral amygdala

Abstract

The basolateral amygdala (BLA) is critical for the generation of emotional behavior and the formation of emotional memory. Understanding the neuronal mechanisms that contribute to emotional information processing in the BLA will ultimately require knowledge of the anatomy and physiology of its constituent neurons. Two major cell classes exist in the BLA, pyramidal projection neurons and nonpyramidal interneurons. Although the properties of projection neurons have been studied in detail, little is known about the properties of BLA interneurons. We have used whole-cell patch clamp recording techniques to examine the physiological properties of 48 visually identified putative interneurons from the rat anterior basolateral amygdalar nucleus. Here, we report that BLA interneurons can be differentiated into four electrophysiologically distinct subtypes based on their intrinsic membrane properties and their response to afferent synaptic input. Interneuron subtypes were named according to their characteristic firing pattern generated in response to transient depolarizing current injection and were grouped as follows: 1) burst-firing interneurons (n = 13), 2) regular-firing interneurons (n = 11), 3) fast-firing interneurons (n = 10), and 4) stutter-firing interneurons (n = 14). Post hoc histochemical visualization confirmed that all 48 recorded neurons had morphological properties consistent with their being local circuit interneurons. Moreover, by using triple immunofluorescence (for biocytin, calcium-binding proteins, and neuropeptides) in conjunction with patch clamp recording, we further demonstrated that over 60% of burst-firing and stutter-firing interneurons also expressed the calcium-binding protein parvalbumin (PV(+)). These data demonstrate that interneurons of the BLA show both physiological and neurochemical diversity. Moreover, we demonstrate that the burst- and stutter-firing patterns positively correlate with PV(+) immunoreactivity, suggesting that these neurons may represent functionally distinct subpopulations.

Networks of Parvalbumin-Positive Interneurons in the Basolateral Amygdala

“…Although these cells were not identified according to the presence of calciumbinding proteins, their firing properties are in general similar to those of the cells we characterized as FS. A stuttering phenotype has also been previously reported in the BLA (Washburn and Moises, 1992) and neurons with similar properties have more recently been shown to express parvalbumin (Rainnie et al, 2006). In our sample, FS cells (75 of 158) ( Fig.…”

“…Of these, parvalbumin-containing (PVϩ) neurons form ϳ50% of the interneuronal population, showing extensive colocalization with calbindin (McDonald and Betette, 2001), but not expressing the other markers. Electrophysiological recordings from interneurons in the BLA both in vitro (Rainnie et al, 1993(Rainnie et al, , 2006Mahanty and Sah, 1998) and in vivo (Lang and Pare, 1998) have also revealed a diversity of firing properties. However, little is known about the identity of these interneurons or their connectivity.…”

Identification of cell-type-specific promoters within the brain using lentiviral vectors

“…11,12,28 A block of tissue containing the hippocampus was then mounted on the chuck of a Leica VTS-1000 vibrating microtome (Leica Microsystems Inc., Bannockburn, IL, USA), and 350 mm coronal slices were cut. Slices were then hemisected and transferred to a holding chamber containing ACSF KA at room temperature and gassed with a 95-5% oxygen/carbon dioxide mixture for 1 h before being placed in oxygenated control ACSF containing (in mM): NaCl (130), KCl (3.5), KH 2 PO 4 (1.1), MgCl 2 (1.3), CaCl 2 (2.5), NaHCO 3 (30) and glucose (10).…”

“…Cell-type-specific lentivirus in brain JP Chhatwal et al electrophysiologic properties of interneurons in the rat brain, [11][12][13] we explored the use of the CCK-GFP virus as a means to label cells for fluorescently guided electrophysiologic recording in vitro. Twelve days following in vivo infection, acute brain slices were prepared and electrophysiologic recordings were obtained from visually identified CCK-GFP-infected neurons of the rat hippocampus.…”

“…Whole-cell patch clamp recordings were obtained with standard techniques, as described previously. 11,12,28 Briefly, recordings were made with an Axopatch-1D amplifier (Molecular Devices, Sunnyvale, CA, USA) using a Digidata 1320A A-D interface and pClamp 8.2 software (Molecular Devices). In cell-attached mode, patch electrode seal resistance was considered acceptable if it was 41.5 GO.…”