Intercalated and paracapsular cell islands of the adult rat amygdala: A combined rapid-Golgi, ultrastructural, and immunohistochemical account

The intercalated nuclear complex of the primate amygdala

“…The prominent clusters of small/medium sized neurons were continuous with more sparsely populated narrow corridors of neurons of various sizes. The IM complex was embedded within an extensive net of stained dendritic processes between the amygdalar nuclei, in agreement with previous studies of IM in rats and humans (Millhouse, 1986, Urban and Yilmazer-Hanke, 1999, Marcellino et al, 2012). …”

“…Cortical-like inhibitory interneurons are found in the basal, lateral and cortical nuclei, as well as the amygdalohippocampal area, and resemble GABAergic neurons of the cortex, based on similar firing patterns, neurochemical markers and synaptic specificity with dendritic, somatic, or axonal elements of nearby pyramidal neurons [reviewed in (Capogna, 2014)]. Striatal-like inhibitory neurons are found primarily in IM, Ce, Me, and Co and morphologically resemble medium-sized spiny striatal neurons (Millhouse, 1986, De Olmos, 1990, Urban and Yilmazer-Hanke, 1999, Marcellino et al, 2012). The diversity of inhibitory neurons suggests that inhibition is a critical regulator of activity in the amygdala (Quirk and Gehlert, 2003, Pape, 2005, Duvarci and Pare, 2014, Wolff et al, 2014) that likely accounts for the low spontaneous firing rates of neurons in the lateral and central nuclei [reviewed in (Pare et al, 2003, Quirk and Gehlert, 2003, Pape, 2005)].…”

“…Several studies have pointed to the unique positioning of IM neurons, their inhibitory nature and complex connectivity patterns, and have demonstrated their central role in circuits involved in fear conditioning, extinction, complex emotional processes and anxiety (Royer et al, 1999, Pare et al, 2004, Likhtik et al, 2008, Busti et al, 2011, Palomares-Castillo et al, 2012). As key nodes of these circuits, IM neurons receive direct excitatory input from the cortex, thalamus, and basal and lateral amygdalar nuclei (Millhouse, 1986, Ghashghaei and Barbas, 2002, Amano et al, 2010, Barbas et al, 2011, Marcellino et al, 2012, Pinard et al, 2012, Asede et al, 2015, Strobel et al, 2015). In turn, IM neurons send inhibitory projections to other IM neurons, and to the output of the amygdala, including the basal (BM, BL), lateral (La), and the inhibitory central (Ce) and medial (Me) nuclei, modulating emotional responses (Millhouse, 1986, Pare and Smith, 1993, Royer et al, 2000b, Amano et al, 2010, Manko et al, 2011).…”

“…Most detailed accounts of IM nuclei in the literature are in rodents (De Olmos et al, 1985, Millhouse, 1986, Manko et al, 2011, Marcellino et al, 2012). The organization of the IM nuclei in primates is largely unexplored, and limited to reports highlighting their considerable variability in morphology, numbers and density (Crosby and Humphrey, 1941, Stephan and Andy, 1977, De Olmos, 1990, Urban and Yilmazer-Hanke, 1999, Carlo et al, 2010).…”

An inhibitory pathway controlling the gating mechanism of the mouse lateral amygdala revealed by voltage-sensitive dye imaging

“…Inhibitory inputs to the La control the strength of sensory inputs and interfere with the initial step of the acquisition of fear memory. Two groups of GABAergic neurons in the amygdala are known: local interneurons that are scattered within the local neuropil [17], and intercalated cells organized in clusters (intercalated clusters) surrounding the amygdala complex [15,16,18,20,23,24]. Although inhibitory inputs to the individual principal neurons in the amygdala have been analyzed electrophysiologically [4,26,31,37,38], how sensory inputs Optical imaging techniques overcome these limitations to investigating propagations in a wide range of neuronal interactions, and have been applied in the study of excitatory circuits of several brain regions [7,9,11,12,29,33,34].…”