Priority CommunicationKappa Opioid Receptor Signaling in the Basolateral Amygdala Regulates Conditioned Fear and Anxiety in Rats
Section snippets
Rats
A total of 198 male Sprague-Dawley rats (325–375 g) (Charles River Laboratories, Raleigh, North Carolina) were used. Rats were singly housed following surgery and maintained on a 12-hour light-dark cycle with unrestricted access to food and water. Protocols were approved by McLean Hospital's Institutional Animal Care Committee and consistent with National Institutes of Health policies.
Quantitative Real-Time Reverse Transcriptase Polymerase Chain Reaction
Thirty-eight rats were used to determine if fear conditioning affects KOR or PDyn mRNA expression in the BLA,
Results
Tissue punches were obtained from the BLA, CeA, HIP, and STR, which have varying degrees of dynorphin expression (27, 29) (Figure 1A,B). Rats that received Light+Shock training displayed marked conditioned fear, as indicated by a 72% increase in startle in the presence of the light (Figure 1C). Rats exposed to Light Alone did not show altered startle in the presence of the light and had significantly lower FPS (4%) than rats receiving Light+Shock training [t(16) = 2.87, p < .05] (Figure 1C),
Discussion
Systemic administration of KOR antagonists produces anxiolytic-like effects in models of fear and anxiety (15). Here, we identify the BLA as a site of increased KOR mRNA expression following fear learning and decreased KOR mRNA expression following effective fear extinction. We also identify the BLA and CeA as regions that mediate the anxiolytic-like effects of KOR antagonists. These findings provide evidence that fear conditioning and extinction dynamically regulate KOR expression in the BLA—a
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2020, Handbook of Behavioral NeuroscienceCitation Excerpt :In contrast, changes in KOR mRNA expression in the BLA have been associated with fear-potentiated startle responses, with higher levels of fear-potentiated startle being associated with higher KOR mRNA expression (Knoll et al., 2011). Injections of the KOR antagonist, JDTic, into the BLA or CEA decreased fear-potentiated startle without affecting baseline startle (Knoll et al., 2011), potentially suggesting a role of DYN acting through KOR in the BLA (or CEA) in modulating conditioned startle responses. These results are consistent with the localization of both DYN and KOR in neurons and fibers in the BLA and CEA (Mansour et al., 1996; Mansour, Fox, Burke, et al., 1994; Mansour, Fox, Meng, et al., 1994), although DYN-containing neurons in the CL are denser than in BLA.
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