The rostral subcommissural ventral pallidum is a mix of ventral pallidal neurons and neurons from adjacent areas: an ele
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ORIGINAL ARTICLE
The rostral subcommissural ventral pallidum is a mix of ventral pallidal neurons and neurons from adjacent areas: an electrophysiological study Yonatan M. Kupchik • Peter W. Kalivas
Received: 22 June 2012 / Accepted: 25 October 2012 Springer-Verlag Berlin Heidelberg 2012
Abstract The ventral pallidum (VP) is a part of the ventral striatopallidal system and is involved in rewardrelated behaviors. The VP is composed of a ventromedial (VPvm) and a dorsolateral (VPdl) subregion, and some rostral-caudal differences are reported. Study of the VP often focuses on the subcommissural VP, typically considered homogenous in spite of known subdivisions. In this work, we used slice electrophysiology combined with immunohistochemistry for marker neuropeptides to test whether the subcommissural VP is functionally homogenous. Using sagittal slices, we show that more lateral levels (2.40 mm) of the subcommissural VP are homogenous but that a more medial slice (1.90 mm) contains two types of neurons. One type, located more caudally, resembles neurons in the lateral subcommissural VP, with long aspiny dendrites, primarily GABAergic input, and characteristic electrophysiological properties, such as depolarized membrane potential and spontaneous action potential discharge. The second type of neuron, located mostly in the rostral subcommissural VP, shows properties that are akin to medium spiny neurons of adjacent regions, including spiny dendrites, major glutamatergic input, hyperpolarized membrane potential, and no spontaneous action potentials. The two types of neurons were present in both the VPvm and VPdl, implying that the mix is not a characteristic of histologically defined subregions. We conclude that at medial levels the rostral subcommissural VP contains a mix of typical ventral pallidal neurons and spiny neurons similar to those in adjacent regions. This observation needs
Y. M. Kupchik (&) P. W. Kalivas Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA e-mail: [email protected]
to be considered when interpreting past experiments and designing future experiments in the subcommissural VP. Keywords Ventral pallidum Electrophysiology Nucleus accumbens Extended amygdala
Introduction The ventral pallidum (VP), first described by Heimer and Wilson (1975), is a part of the ventral striatopallidal system and has been proposed to be a structure critical for translating motivation into motor output (Mogenson et al. 1980; Mogenson and Yang 1991). Supporting this contention, the VP is involved in the expression of motor behaviors (Napier 1993) and sensorimotor information processing (Forcelli et al. 2012; Kodsi and Swerdlow 1997), as well as plays a central role in reward-related behaviors, including addiction to drugs of abuse (Hiroi and White 1993; Root et al. 2012b; McFarland and Kalivas 2001; Hubner and Koob 1990; Martin et al. 2008; Panagis et al. 1995; Root et al. 2010, 2012a; Skoubis and Maidment 2003; Smith et al. 2009; Tang et al. 2005; Wilson and Rolls 1
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