Contribution of amygdala neurons containing peptides and calcium‐binding proteins to fear‐potentiated startle and exploration‐related anxiety in inbred Roman high‐ and low‐avoidance rats

Abstract

The purpose of this study was to investigate amygdala‐related fear and anxiety in two inbred rat lines differing in emotionality (RHA/Verh and RLA/Verh), and to relate the behaviour of the animals to neuronal types in different nuclei of the amygdala. The behavioural tests used were the motility test, elevated plus‐maze and fear‐potentiated startle response. The neurons investigated were immunoreactive for the anxiogenic peptide corticotropin‐releasing factor (CRF‐ir), the anxiolytic peptide neuropeptide Y (NPY‐ir), and the calcium‐binding proteins parvalbumin (PARV‐ir) and calbindin (CALB‐ir). The NPY‐ir, PARV‐ir and CALB‐ir neurons studied were subpopulations of GABAergic neurons. RLA/Verh rats, which showed a significant fear‐potentiation of the acoustic startle response, had more CRF‐ir projection neurons in the central nucleus of the amygdala. The same RLA/Verh rats were either less or equally anxious in the motility test (similar to open field) and elevated plus‐maze as compared with RHA/Verh rats. In accordance with this behaviour, the RLA/Verh rats had more NPY‐ir neurons in the lateral, and more PARV‐ir neurons in basal nuclei of the amygdala than RHA/Verh rats, but no differences were detected in the number of CRF‐ir and CALB‐ir neurons of the basolateral complex. In conclusion, the RLA/Verh rats displayed an opposite behaviour in the fear‐potentiated startle model and the exploratory tests measuring anxiety based on choice behaviour. Thus, the anxiogenic systems in the central nucleus and anxiolytic systems in the basolateral complex of the amygdala might be differentially involved in the fear‐potentiated startle paradigm and exploratory tests in the Roman rat lines.

Maternal deprivation and early handling affect density of calcium binding protein-containing neurons in selected brain regions and emotional behavior in periadolescent rats

“…Subpopulations of GABAergic neurons in the amygdala express different CBPs and neuropeptides (Yilmazer-Hanke et al, 2002). We demonstrated that the density of PV containing neurons was significantly increased in the lateral nucleus of the amygdala of both EH and DEP rats compared with NH rats.…”

“…4) where the majority of amygdalar PV and CB positive GABAergic neurons are found (Yilmazer-Hanke et 2002). Oneway ANOVA revealed a significant main effect of separation of PV neuronal density in the lateral nucleus (F(2,25)=5.14; P=0.014) but not in the basal nucleus.…”

“…In fact, PV-positive neurons in the basolateral complex are interneurons receiving excitatory synaptic input from amygdaloid projections and form local inhibitory circuits on pyramidal projection neurons (Smith et al, 2000). Accordingly, GABAergic tone in the basolateral amygdala can reduce emotional arousal in the social interac tion test (Sanders and Shekhar, 1995a,b;File and Seth, 2003) and increased PV neuronal densities in the basolateral complex have been previously implicated in reduced anxiety behavior in the motility test (Yilmazer-Hanke et al, 2002). Thus, the changes of GABAergic circuits involving PV positive interneurons in the lateral nucleus correlate with the expression of reduced anxiety we observed in EH and DEP rats (see below).…”

Role of corticotropin releasing factor in anxiety disorders: A translational research perspective

“…The extended amygdala (specifically the bed nucleus stria terminalis) is required for both CRFand stress-induced increases in startle (de Jongh et al, 2003;Gewirtz et al, 1998;Lee and Davis, 1997;Toufexis et al, this volume). Rats bred for differing levels of emotionality have been shown to differ in both CRF peptide levels in the amygdala and fear-potentiated startle performance, suggesting that these two markers may be linked (Yilmazer-Hanke et al, 2002). Indeed, CRF receptor activation in the amygdala appears to enhance consolidation of learned fear (Roozendaal et al, 2002), hence increased CRF tone in the amygdala may facilitate acquisition and/or extinction of FPS.…”

The Neuropsychiatry and Neuropsychology Of Lipoid Proteinosis

“…Results from animal studies strongly suggest that different types of fear-conditioned behaviour are mediated by separate nuclei within the amygdala, and that the anxiogenic systems in the various nuclei may be differentially involved 84 . The basolateral complex (BL) of the amygdala seems to be significant for linking objects with current stimulusvalue, and the behaviours and goal-directed actions associated with the value 85 …”