INTRODUCTION: Noradrenergic receptors (α‑AR) in the ventral tegmental area (VTA) regulate phasic dopamine release in the mesolimbic, but not in the mesocortical pathway. Accordingly, the α‑ARs modulate conditioned behaviours, such as acquisition of fear memories. Importantly, the role of the VTA noradrenergic signaling in fear memory retrieval remain unclear. AIM(S): The aim of the study was to investigate the role of α1‑AR and α2-AR in VTA in the retrieval of conditioned stimulus (CS)‑induced fear memories. In control studies, we investigate their role in the locomotor activity and anxiety‑like behaviour. METHOD(S): We performed fear conditioning and open field tests in adult male, Spraque‑Dawley rats combined with intra‑VTA microinfusions. The fear conditioning consisted of two phases: training during which CS was associated with footshock, and retrieval of the conditioned fear memory. Retrieval test was preceded by intra‑VTA administration of α1‑AR and α2-AR antagonist (terazosin 1 µg/side and RX 821002 2.7 µg/side) and conducted in a novel context in which presentation of CS induced fear responses. RESULTS: We demonstrated that α1-AR blockade in the VTA decreased freezing responses during retrieval of CS‑induced fear memory. In contrast, α2AR blockade had no effects. Furthermore, neither blockade of α1-AR and α2-AR had no effects on locomotor activity and anxiety‑like behavior. CONCLUSIONS: Here, we demonstrated a potential role of the VTA noradrenergic signaling in fear memory retrieval. These results indicate that the noradrenergic signalling in the VTA modulates CS-fear induced responses predominantly via α1‑AR.
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