| Summary: | 碩士 === 國立陽明大學 === 神經科學研究所 === 102 === The amygdala is a key brain structure involved in emotional processing, conditioned fear learning and memory. The amygdala can be divided into different subregions, including basal amygdala (BA), lateral amygdala (LA), the central nucleus of the amygdala (CeA) and intercalated cell masses (ICMs). The CeA can be further divided into the lateral part (CeL) and medial part (CeM). The majority of neurons in the CeL, considered to regulate the expression of fear expression, are GABAergic neurons. Using whole-cell recordings, we found that CeL neurons display diverse firing patterns and intrinsic properties. These neurons were classified based on their electrophysiology properties. At least, two major types of neurons were identified in the CeL; late-spiking (LS) neurons exhibit a slow ramping depolarization phenotype and longer spike latency compared to early-spiking (ES) neurons.
It is known that firing pattern of a given neuron is determined by the morphological architecture and a repertoire of intrinsic membrane conductances. Since activation and inactivation of voltage-gated potassium (Kv) channels can shape the spike waveform and spike precision, their expression is one of the main factors in determining the firing phenotypes. The specific aim of this study is to characterize the functional properties of Kv channels in CeL cells. Application of a potassium channel blockers 4-aminopyramidine (4-AP) at a low concentration (30 M) and -dendrotoxin (-DTX; 100 nM) can reduced the spike delay of LS neurons but had little effect on ES neurons. The result indicates that 4-AP- and -DTX-sensitive, Kv1-like K+ current plays an important role in mediating the spike delay, thus defining the firing pattern of CeL neurons. While in nucleated patch recordings, no significant difference of somatic Kv channels properties or subtype composition were found between both types of CeL neurons, except in the decay time of A-type K+ current. This result suggests that the major difference in the expression of 4-AP- and -DTX-sensitive K+ channels between LS and ES cells is not located primarily on the soma. Further, immunohistochemical staining of the axon initial segment (AIS) marker Ankyrin-G (Ank-G) and Kv1 channels showed that Kv1 channels did not co-localized with Ank-G, suggesting that the Kv1 channels are not expressed on the AIS.
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