Calcium‐binding proteins define interneurons in HVC of the zebra finch (Taeniopygia guttata)

Abstract

Nucleus HVC of the avian song system is essential to song patterning and is a prime site for auditory-vocal integration important to vocal learning. These processes require precise, high-frequency action potential activity, which, in other systems, is often correlated with the expression of calcium-binding proteins. To characterize any such functional specializations in HVC, we retrogradely labeled projection neurons innervating HVC's known targets, namely, area X or nucleus robustus arcopallialis (RA), then stained HVC sections with antibodies to the calcium-binding proteins parvalbumin, calbindin, and calretinin. Under epifluorescent illumination, neither projection neuron type exhibited detectable levels of calcium-binding protein immunoreactivity, whereas a third cell type, made up of nonprojection neurons (interneurons), was immunopositive for one, two, or all three of the calcium-binding proteins. In fact, most of these interneurons were either doubly or triply labeled. To explore the link between the electrical and calcium-binding protein properties of individual HVC neurons, we used intracellular methods in brain slices to record from identified HVC cell types based on their intrinsic electrical properties. Intracellular neurobiotin combined with immunostaining revealed that fast-spiking interneurons, but not the slower-spiking projection neurons, were positive for one or more calcium-binding proteins. Confocal microscopy confirmed these results and also revealed that RA-projecting cells might contain very low levels of parvalbumin. These results indicate that HVC interneurons are specialized in their calcium-binding proteins and suggest how it might be possible to resolve the details of HVC microcircuits underlying song selectivity and auditory-vocal learning.

Replaceable neurons and neurodegenerative disease share depressed UCHL1 levels

“…Henceforth, these neurons will be referred to as HVC-RA and HVC-X neurons. HVC-RA neurons are smaller and more numerous than HVC-X neurons, and the two cell classes do not overlap (21), as shown in Fig. 1b.…”

The HVC Microcircuit: The Synaptic Basis for Interactions between Song Motor and Vocal Plasticity Pathways

“…In some experiments, we combined intracellular staining with Neurobiotin and immunohistochemical methods to determine which cells in HVC were positive for parvalbumin (PV), a calcium-binding protein previously localized to HVC interneurons (Wild et al, 2005). After cell fills, brain slices were transferred to 4% paraformaldehyde within 30 min, where they remained for a minimum of 24 h before being placed in 30% sucrose for several hours and then sectioned at 50 m on a freezing microtome.…”

Auditory-Dependent Vocal Recovery in Adult Male Zebra Finches Is Facilitated by Lesion of a Forebrain Pathway That Includes the Basal Ganglia

“…Bilateral microlesions in HVC were placed by positioning an electrode (Teflon-insulated tungsten; 200 m diameter; A-M Systems, Everett, 4 RA-projecting neurons outnumber area X-projecting neurons by Ͼ4:1 and both populations are distributed throughout the volume encompassed by HVC (Wild et al, 2005). Within RA, individual neurons receive synaptic input from both HVC and LMAN (Mooney and Konishi, 1991;Stark and Perkel, 1999); these inputs are nontopographic and topographic, respectively (Johnson et al, 1995;Foster and Bottjer, 1998).…”

“…The potential effects of microlesion damage within HVC are informed by the following anatomical and behavioral considerations: Adult male zebra finch HVC contains interneurons and distinct populations of RAand X-projecting neurons; RA-projecting neurons outnumber area X-projecting neurons by Ͼ4:1, and both projection populations are distributed throughout the volume encompassed by HVC (Wild et al, 2005). Interneurons form local microcircuits connecting RA-and X-projecting populations (Mooney and Prather, 2005).…”