Cell-type specificity of neuronal excitability and morphology in the central amygdala

Abstract

21Central amygdala (CeA) neurons expressing protein kinase C delta (PKCδ + ) or Somatostatin 22 (Som + ) differentially modulate diverse behaviors. The underlying features supporting cell-type-23 specific function in the CeA, however, remain unknown. Using whole-cell patch-clamp 24 electrophysiology in acute mouse brain slices and biocytin-based neuronal reconstructions, we 25 demonstrate that neuronal morphology and relative excitability are two distinguishing features 26 between Som + and PKCδ + CeLC neurons. Som + neurons, for example, are more excitable, 27 compact and with more complex dendritic arborizations than PKCδ + neurons. Cell size, intrinsic 28 membrane properties, and anatomical localization were further shown to correlate with cell-type-29 specific differences in excitability. Lastly, in the context of neuropathic pain, we show a shift in the 30 excitability equilibrium between PKCδ + and Som + neurons, suggesting that imbalances in the 31 relative output of these cells underlie maladaptive changes in behaviors. Together, our results 32 identify fundamentally important distinguishing features of PKCδ + and Som + cells that support cell-33 type-specific function in the CeA. 34 35 Keywords: central amygdala, Somatostatin, protein kinase C delta, intrinsic excitability, 36 morphology, neuropathic pain 37 2002, Chieng et al., 2006, Schiess et al., 1999, Li and Sheets, 2018. Recent studies have further 64 shown that CeLC neurons with different firing properties are topographically organized based on 65 their projection targets (Li and Sheets, 2018), suggesting that heterogeneity of function within the 66 CeLC might also be anatomically defined. 67In the present study, we contributed to the growing body of knowledge about the CeLC by 68 performing a characterization of the electrophysiological and morphological properties of PKCδ + 69and Som + neurons. Our overarching hypothesis is that these two genetically distinct populations 70 of CeLC neurons are electrophysiologically and morphologically different. We used whole-cell 71 patch-clamp electrophysiology in acute mouse brain slices in combination with biocytin-based 72 morphological reconstructions to characterize and compare the passive and active membrane 73properties, as well as the evoked repetitive firing responses, single action potential waveforms 74 and neuronal morphologies of these two subpopulations of neurons. We further evaluated 75 whether membrane properties and excitability are dependent on the anatomical localization within 76 the central amygdala, both at the subnuclei and rostro-caudal levels. 77Finally, using a mouse model of neuropathic pain, we tested whether perturbations known 78 to alter CeLC-dependent behavioral outputs would result in a shift in the relative excitability of 79 these two CeLC cell types. Using this cell-type-specific approach, we demonstrated that PKCδ + 80 and Som + neurons have distinct electrophysiological and morphological properties and that the 81 differences in the excitability of these cells are occlud...

Optogenetic Manipulations of Amygdala Neurons Modulate Spinal Nociceptive Processing and Behavior Under Normal Conditions and in an Arthritis Pain Model

“…A cell–type specific analysis is needed for the better understanding of amygdala pain mechanisms, and the optogenetic strategy employed here is an important step in that direction. The involvement of individual cell–types (PKCδ, SOM, CRF; see Introduction ) in pain–related amygdala neuroplasticity has not been fully explored and is currently an area of extensive research ( Wilson et al, 2019 ; Li and Sheets, 2020 ; Adke et al, 2021 ). Here we show that optogenetic activation of CRF neurons or of BLA input to the CeA generates nocifensive emotional responses (vocalizations) and mechanical hypersensitivity under normal conditions in the absence of tissue injury or pathology, whereas silencing of CRF neurons or of BLA input to CeA inhibits vocalizations in an arthritis pain model.…”

Acid-sensing ion channel 1a in the central nucleus of the amygdala regulates anxiety-like behaviors in a mouse model of acute pain

“…The molecular features and morphological localization of GABA CeA neurons are genetically, physiologically, and functionally heterogeneous (Janak and Tye, 2015;Wilson et al, 2019;Li and Sheets, 2020). Different species of GABA CeA neurons, including those expressing adrenocorticotropinreleasing hormone (CRH), protein kinase C delta (PKCδ), somatostatin (SOM), and neurohypophysin (Duvarci and Pare, 2014;Kim et al, 2017;McCullough et al, 2018), may have different roles in pain and anxiety regulation (Wilson et al, 2019;Adke et al, 2021). For example, in a mouse model of the nerve injury, PKCδ CeA neurons were sensitized, leading to nociceptive hyperalgesia, but the excitability of SOM CeA neurons was suppressed, resulting in hypoalgesia (Wilson et al, 2019).…”

Chronic THC vapor inhalation rescues hyperalgesia in rats with chronic inflammation and produces sex-specific alterations in midbrain neuronal activity

“…A subset of both protein kinase C delta-positive (PKCδ + ) and somatostatin-positive (SOM + ) neurons in the CeA of mice exhibit late-firing phenotypes (Ciocchi et al, 2010;Haubensak et al, 2010;Amano et al, 2012). In the CeA of mice, SOM + late-firing neurons have higher excitability than PKCδ + late-firing neurons, but this difference is abolished in a sciatic nerve cuff model of neuropathic pain 6-14 days after injury (Adke et al, 2021). In the same model of neuropathic pain, PKCδ + CeA neurons were pro-nociceptive and this seemed to be due to an increase in excitability of late-firing PKCδ + but not regularspiking PKCδ + neurons (Wilson et al, 2019).…”