Gergő A. Nagy, Dániel Magyar, Orsolya I. Papp, Judit M. Veres, Zsófia Reéb and Norbert Hájos
‘Lendület’ Laboratory of Network Neurophysiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest
The basolateral amygdala (BLA) is composed of distinct nuclei, such as the lateral (LA) and basal nuclei (BA). The BLA plays a critical role in Pavlovian fear conditioning. In this robust learning paradigm a neutral conditioned stimulus (CS) becomes associated to a biologically relevant unconditioned stimulus (US). Noxious stimuli proved to be a highly potent US and thus are widely applied in studies of fear learning. A prevalently used noxious stimuli is the administration of mild electrical shocks. However, since this electrical stimulation compromises recording devices, our knowledge is limited how the US is conveyed to the BLA.
To address these questions we employed an approach to deliver mild electrical shocks to the animals that allow its combination with extracellular and juxtacellular recordings. In awake, head-fixed mice we used silicon probes to simultaneously record single-unit activity in the LA and BA during presentation of noxious stimuli. In order to validate our extracellular recordings, in anesthetized mice we juxtacellularly recorded and labeled randomly sampled neurons in the LA and BA during the administration of electrical shocks.
Our data revealed that two populations of responsive principal cells (PCs) could be distinguished based on the latency of their stimulus-evoked firing. In the first population, PCs responded with short-latency to the noxious stimuli (~ 25-30 ms), while the stimulus related elevation of firing rates in the second group occurred with a longer latency (~ 2 s). Both cell groups were present in both LA and BA. These results indicate that the LA and BA receive the noxious inputs simultaneously.
In summary, in our study we successfully employed an approach, which allowed us to electrophysiologically investigate the spiking activity of amygdala neurons during the administration of mild electrical shocks. Together our results indicate that in the BLA different nuclei receive noxious information simultaneously.
Doctoral School: Neurosciences ("János Szentágothai")
Program: Functional Neurosciences
Supervisor: Prof. Norbert Hájos