Functional Properties and Projections of Neurons in the Medial Amygdala

Abstract

The medial nucleus of the amygdala (MeA) plays a key role in innate emotional behaviors by relaying olfactory information to hypothalamic nuclei involved in reproduction and defense. However, little is known about the neuronal components of this region or their role in the olfactory-processing circuitry of the amygdala. Here, we have characterized neurons in the posteroventral division of the medial amygdala (MePV) using the GAD67-GFP mouse. Based on their electrophysiological properties and GABA expression, unsupervised cluster analysis divided MePV neurons into three types of GABAergic (Types 1-3) and two non-GABAergic cells (Types I and II). All cell types received olfactory synaptic input from the accessory olfactory bulb and, with the exception of Type 2 GABAergic neurons, sent projections to both reproductive and defensive hypothalamic nuclei. Type 2 GABAergic cells formed a chemically and electrically interconnected network of local circuit inhibitory interneurons that resembled neurogliaform cells of the piriform cortex and provided feedforward inhibition of the olfactory-processing circuitry of the MeA. These findings provide a description of the cellular organization and connectivity of the MePV and further our understanding of amygdala circuits involved in olfactory processing and innate emotions.

Social Isolation During Postweaning Development Causes Hypoactivity of Neurons in the Medial Nucleus of the Male Rat Amygdala

“…Based on the degree of spike frequency adaptation, small hyperpolarization-activated voltage sag, and shape of fast afterhyperpolarization potentials, the neurons recorded in this study are most likely principle projection neurons of the MeA (Bian et al, 2008;Keshavarzi et al, 2014). Although there is a degree of overlap, many neurons of the MeApd project to the ventrolateral part of the ventral medial hypothalamus (VMH) region important in mating behavior, whereas many neurons of the MeApv project to the dorsomedial VMH region important in agonistic behavior.…”

“…This measure was best fit to a second-order polynomial to derive the current amplitude that evokes a 50% response (EC 50 ) and the extrapolated maximal number of action potentials (B max ). Neurons that displayed electrophysiological parameters that match GABAergic interneurons of the MeA (Keshavarzi et al, 2014) or displayed 415% variability across time in holding current, V rest , input resistance or access resistance were not included for analysis. Data were analyzed using Prism (version 6.0; GraphPad Software, La Jolla, CA), with a po0.05 considered statistically significant.…”

Medial Amygdalar Aromatase Neurons Regulate Aggression in Both Sexes

“…In keeping with its size and functional diversity, the mouse MeA is molecularly heterogeneous (Carney et al, 2010; Choi et al, 2005; Keshavarzi et al, 2014; Xu et al, 2012; Yang et al, 2013). These considerations make it difficult to selectively target the small pool of aromatase+ MeApd neurons (Wu et al, 2009).…”

Neuronal Representation of Social Information in the Medial Amygdala of Awake Behaving Mice

“…AOB mitral cells project primarily to the medial amygdala (MeA), which in turn connects to hypothalamic regions associated with the control of social behaviors (Keshavarzi et al, 2014). The MeA has been subdivided into distinct functional regions along the anterior-posterior and dorsal-ventral axes, with the medial amygdala posterodorsal (MeApd) primarily involved in conspecific social behaviors such as mating and aggression (Choi et al, 2005; Hong et al, 2014).…”