0136 OPTOGENETIC STIMULATION AND INHIBITION OF THE CENTRAL NUCLEUS OF THE AMYGDALA ALTERS FIRING IN LOCUS COERULEUS NEURONS

Abstract Introduction: The amygdala, via the CNA, has direct projections to the LC and other regions (e.g., LDT, PPT, DRN, and subcoeruleus) in the mesopontine brainstem that play significant roles in regulating both sleep and arousal and the stress response. Here we used optogenetics to assess how CNA regulates neural activity in LC in anesthetized rats. Methods: To specifically target CNA projections to LC, CNA was infected with AAV-EF1a-DIO-hChR2(H134R)-EYFP and/or AAV-EF1a-DIO-eNpHR3.0-EYFP and the LC with AAV-EF1a-mCherry-IRES-WGA-Cre that mediates bicistronic expression of mCherry and WGA-Cre. Vectors in CNA coded for double floxed and inverted open reading frame opsins, hChR2 or eNpHR3.0. When a neuron in the LC/peri-LC zone synapses with neurons in CNA and expressed WGA-Cre, it is transneurally transferred to CNA neurons, where Cre activity flips the opsin gene(s) into its correct orientation thereby allowing its translation. Subsequent expression of the opsin(s) gene enables excitation of ChR2 expressing neurons/projections by blue light or inhibition of the NpHR expressing neurons/projections from CNA by yellow light. For recording, the rats were anesthetized with isoflurane, and optic fibers and recording electrodes were stereotaxically lowered into place. When stable recordings of single neurons were obtained, either CNA or terminal fibers were presented with blue or yellow light for stimulation or inhibition, respectively. Results: Ninety-six cells were recorded in seven rats. Responses of ≥25% change in firing rates were found in 58 neurons that received stimulation. Blue light stimulation of different durations suppressed firing in neurons in the vicinity of LC (1 sec (n=3), 2 sec (n=12) and 5 sec, (n=13)). By comparison, yellow light stimulation of 30 sec enhanced, firing in neurons in vicinity of LC (n=30). Conclusion: These data demonstrate that CNA can influence activity in LC/peri-LC zone with potential relevance for its role in sleep, arousal and the stress response. Support (If Any): MH1057701, MH64827.