Biology subjects

Pyeon, G. H.

Publications and source records attributed to Pyeon, G. H..

3 recordsLinked to original sources

bioRxiv2024

Encoding opposing valences through frequency-dependent transmitter switching in single peptidergic neurons

Peptidergic neurons often co-express fast transmitters and neuropeptides in separate vesicles with distinct release properties. However, the release dynamics of each transmitter in various contexts have not been fully understood in behaving animals. Here, we demonstrate that calcitonin gene-related peptide (CGRP) neurons in the external lateral subdivision of the parabrachial nucleus (CGRPPBel) encode opposing valence via differential release, rather than corelease, of glutamate and neuropeptides, according to firing rate. Glutamate is released preferentially at lower firing rates with minimal release at higher firing rates, whereas neuropeptides are released at higher firing rates, resulting in frequency-dependent switching of transmitters. Aversive stimuli evoke high frequency responses with accompanying neuropeptide release to encode negative valence, whereas appetitive stimuli evoke low frequency responses with glutamate release to encode positive valence. Our study reveals a previously unknown capability of single CGRPPBel neurons to bidirectionally encode valence via frequency-dependent differential release of transmitters in vivo.

neuroscience↗

bioRxiv2024

A dopamine-dependent mechanism for reward-induced modification of fear memories

How positive and negative affective stimuli interact in the brain to influence behavioral outcomes remains poorly understood. Here, we show that recall of a positive reward-associated conditioned stimulus (CSRew+) can prevent or reverse fear generalization in mice. Modification of generalized fear by recall of a CSRew+ is dependent on the midbrain dopamine system and the regulation of discriminatory threat encoding by the central amygdala (CeA). Precisely timed, transient elevations in dopamine and activation of dopamine D2 receptors in the CeA are necessary to reverse threat generalization and non-discriminatory threat encoding in the CeA. Recall of a positive association is also effective at enhancing the extinction of a conditioned threat response in a dopamine dependent manner. These data demonstrate that recall of a positive experience can be an effective means to suppress generalized fear and show that dopamine projections to the CeA are an important neural substrate for this phenomenon.

neuroscience↗

bioRxiv2024

Parabrachial CGRP neurons modulates conditioned active defensive behavior under a naturalistic threat

Recent studies suggest that calcitonin gene-related peptide (CGRP) neurons in the parabrachial nucleus (PBN) represent aversive information and signal a general alarm to the forebrain. If CGRP neurons serve as a true general alarm, activation of CGRP neurons can trigger either freezing or fleeing defensive behavior, depending on the circumstances. However, the majority of previous findings have reported that CGRP neurons modulate only freezing behavior. Thus, the present study examined the role of CGRP neurons in active defensive behavior, using a predator-like robot programmed to chase mice in fear conditioning. Our electrophysiological results showed that CGRP neurons encoded the intensity of various unconditioned stimuli (US) through different firing durations and amplitudes. Optogenetic and behavioral results revealed that activation of CGRP neurons in the presence of the chasing robot intensified fear memory and significantly elevated conditioned fleeing behavior during recall of an aversive memory. Animals with inactivated CGRP neurons exhibited significantly low levels of fleeing behavior even when the robot was set to be more threatening during conditioning. Our findings expand the known role of CGRP neurons in the PBN as a crucial part of the brains alarm system, showing they can regulate not only passive but also active defensive behaviors.

neuroscience↗