Axonal branching patterns of nucleus accumbens neurons in the rat

Abstract

The patterns of axonal collateralization of nucleus accumbens (Acb) projection neurons were investigated in the rat by means of single-axon tracing techniques using the anterograde tracer biotinylated dextran amine. Seventy-three axons were fully traced, originating from either the core (AcbC) or shell (AcbSh) compartment, as assessed by differential calbindin D28k-immunoreactivity. Axons from AcbC and AcbSh showed a substantial segregation in their targets; target areas were either exclusively or preferentially innervated from AcbC or AcbSh. Axon collaterals in the subthalamic nucleus were found at higher than expected frequencies; moreover, these originated exclusively in the dorsal AcbC. Intercompartmental collaterals were observed from ventral AcbC axons into AcbSh, and likewise, interconnections at pallidal and mesencephalic levels were also observed, although mostly from AcbC axons toward AcbSh targets, possibly supporting crosstalk between the two subcircuits at several levels. Cell somata giving rise to short-range accumbal axons, projecting to the ventral pallidum (VP), were spatially intermingled with others, giving rise to long-range axons that innervated VP and more caudal targets. This anatomical organization parallels that of the dorsal striatum and provides the basis for possible dual direct and indirect actions from a single axon on either individual or small sets of neurons.

Effect of early embryonic deletion of huntingtin from pyramidal neurons on the development and long-term survival of neurons in cerebral cortex and striatum

“…The anti-D1 antibody was a rat monoclonal directed against the 97-amino acid C-terminal fragment of human D1 (Sigma-Aldrich, D187), whose specificity has been demonstrated previously (Levey et al, 1993; Hersch et al, 1995). The anti-ENK used was a rabbit polyclonal antibody against leucine-enkephalin (ImmunoStar, 20066) whose specificity has also been shown previously (Reiner, 1987; Reiner et al, 2007; Tripathi et al, 2010). Immunolabeling for DARPP32 was carried out using an anti-DARPP32 (generously provided by P. Greengard and H. Hemmings), whose specificity has been previously documented (Ouimet et al, 1984).…”

Dopamine D2 and acetylcholine α7 nicotinic receptors have subcellular distributions favoring mediation of convergent signaling in the mouse ventral tegmental area

“…Inhibitory-type terminals may derive from local GABAergic interneurons (Steffensen et al, 1998; Omelchenko and Sesack, 2009) or from GABAergic neurons located in multiple structures, such as striatum, pallidum, periaqueductal gray, rostromedial tegmental nucleus or mesopontine tegmentum among others (Kalivas et al, 1993; Geisler and Zahm, 2005; Tripathi et al, 2010; Xia et al, 2011). The conclusion that GABA is present in some of the D 2 R-labeled terminals that contact dendrites is consistent with studies showing D 2 R-dependent regulation of GABAergic currents in VTA neurons (Michaeli and Yaka, 2010, 2011).…”

The Nucleus Accumbens: Mechanisms of Addiction across Drug Classes Reflect the Importance of Glutamate Homeostasis

“…The NAcore sends projections primarily to GABAergic basal ganglia nuclei, but it also contains neurons that send inputs directly to glutamatergic neurons in the subthalamus and dopaminergic neurons in the paranigral part of the VTA (Groenewegen et al, 1999;Tripathi et al, 2010;Watabe-Uchida et al, 2012;Bocklisch et al, 2013;Matsui et al, 2014;Kupchik et al, 2015). The NAcore also projects to the substantia nigra pars reticulata and sends a striatopallidal projection to the dorsolateral VP and lateral globus pallidus (Heimer et al, 1991;Tripathi et al, 2010). With regard to addiction circuitry, recent optogenetic data from our laboratory show that the pallidal, but not the nigral, projection drives cocaine seeking (Stefanik et al, 2013a).…”