Submitted on October 17, 2008
Revised on December 19, 2008
Accepted on January 7, 2009
Distinct Subtypes of Cholecystokinin-containing Interneurons of the Basolateral Amygdala Identified using a CCK Promoter-Specific Lentivirus
Aaron M. Jasnow1*, Kerry J. Ressler2, Sayamwong E. Hammack3, Jasmeer p. Chhatwal2, and Donald G Rainnie2
1 Emory University
2 Emory
3 University of Vermont
* To whom correspondence should be addressed. E-mail: ajasnow{at}emory.edu.
The basolateral amygdala (BLA) is critical for the formation of emotional memories. Little is known about the physiological properties of BLA interneurons, which can be divided into 4 subtypes based on their immunocytochemical profiles. Cholecystokinin (CCK) interneurons play critical roles in feed-forward inhibition and behavioral fear responses. Evidence suggests that interneurons within a subgroup can display heterogeneous physiological properties. However, little is known about the physiological properties of CCK interneurons in the BLA, and/or if they represent a homogeneous or heterogeneous population. To address this question, we generated a lentivirus expressing GFP under the control of the CCK promoter to identify CCK neurons in vivo. We combined this with whole-cell patch clamp recording techniques to examine the physiological properties of CCK-containing interneurons of the rat BLA. Here, we describe the physiological properties of 57 cells recorded in current clamp mode; we used hierarchical cluster and discriminant function analysis to demonstrate that CCK interneurons can be segregated into 3 distinct subtypes (Type I, II, III) based on their passive and active membrane properties. Additionally, Type II neurons could be further separated into adapting and non adapting types based on their rates of spike frequency adaptation. These data suggest that CCK interneurons of the BLA are a heterogeneous population and may be functionally distinct subpopulations that differentially contribute to the processing of emotionally salient stimuli.
