Properties of GABAergic Neurons in the Rostral Solitary Tract Nucleus in Mice

Abstract

The rostral nucleus of the solitary tract (rNST) plays a pivotal role in taste processing. The rNST contains projection neurons and interneurons that differ in morphology and intrinsic membrane properties. Although characteristics of the projection neurons have been detailed, similar information is lacking on the interneurons. We determined the intrinsic properties of the rNST GABAergic interneurons using a transgenic mouse model that expresses enhanced green fluorescent protein under the control of a GAD67 promoter. Glutamic acid decarboxylase-green fluorescent protein (GAD67-GFP) neurons were distributed throughout the rNST but were concentrated in the ventral subdivision with minimal interaction with the terminal field of the afferent input. Furthermore, the density of the GAD67-GFP neurons decreased in more rostral areas of rNST. In whole cell recordings, GAD67-GFP neurons responded with either an initial burst (73%), tonic (18%), or irregular (9%) discharge pattern of action potentials (APs) in response to membrane depolarization. These three groups also differed in passive and AP characteristics. Initial burst neurons had small ovoid or fusiform cell bodies, whereas tonic firing neurons had large multipolar or fusiform cell bodies. Irregular firing neurons had larger spherical soma. Some of the initial burst and tonic firing neurons were also spontaneously active. The GAD67-GFP neurons could also be categorized in subgroups based on colocalization with somatostatin and parvalbumin immunolabeling. Initial burst neurons would transmit the early dynamic portion of the encoded sensory stimuli, whereas tonic firing neurons could respond to both dynamic and static components of the sensory input, suggesting different roles for GAD67-GFP neurons in taste processing.

The μ-opioid receptor agonist DAMGO presynaptically suppresses solitary tract-evoked input to neurons in the rostral solitary nucleus

“…Thus it would appear that this mouse is a more effective model for comparing properties of GABAergic with non-GABAergic neurons than some other commercially available strains. For example, the "GIN" mouse expresses EGFP mainly in somatostatin GABAergic neurons in the neocortex (Oliva et al 2000), and in the rNST EGFP expression is confined to just half of the GABAergic cells (Wang and Bradley 2010a) and is particularly abundant in the ventral subnucleus (Travers et al 2007;Wang and Bradley 2010a). This preferential distribution contrasts sharply with the homogeneous pattern observed in the GAD67-EGFP knockin mouse in the present investigation (Fig.…”

“…We used a transgenic mouse expressing EGFP under the control of the endogenous promoter for GAD67, a synthetic enzyme for GABA. In contrast to the commercially available "GIN" mouse, which only expresses GFP in a particular subset of rNST GABAergic neurons (Travers et al 2007;Wang and Bradley 2010a), this GAD67-GFP knockin strain has been shown to produce EGFP in virtually all cells expressing GAD67 (Brown et al 2008;Kaneko et al 2008;Ono et al 2005;Tamamaki et al 2003), allowing for a more complete identification of GABAergic neurons in the NTS. Because of reports that monosynaptic inputs to GABAergic neurons in the rNST may diminish during development in rat (Wang et al 2012) but evidence for presynaptic inhibition of monosynaptic vagal inputs to cNST GABAergic neurons in mature as well as young mice (Glatzer et al 2007), we included both mouse pups (P14 -18) and adult mice (6 -11 wk) in our study.…”

Neuropathology in respiratory-related motoneurons in young Pompe (Gaa) mice

“…2D). Thus, all Gaa −/− tissues demonstrated robustly positive staining for CC3 in a region that included the medial NTS and cuneate nucleus (Ganchrow et al, 2014; Tokita et al, 2009; Wang and Bradley, 2010; Zaidi et al, 2008). The Tunel stain showed a similar pattern with positive staining in an area that extended from the area postrema through the NTS (Fig.…”

μ-Opioid modulation in the rostral solitary nucleus and reticular formation alters taste reactivity: evidence for a suppressive effect on consummatory behavior

“…It seems likely that MOR ligands could modulate GABA release in the rNST/RF as well. GABA neurons and enkephalin/endomorphin fibers are densely distributed in the rNST and RF and have overlapping distributions (44,48,56,65,70). Moreover, a recent electron microscopic study suggested that some enkephalin terminals may actually synapse onto GABAergic neurons in the rNST (28).…”