Differential Roles of the Two Raphe Nuclei in Amiable Social Behavior and Aggression – An Optogenetic Study

Abstract

Serotonergic mechanisms hosted by raphe nuclei have important roles in affiliative and agonistic behaviors but the separate roles of the two nuclei are poorly understood. Here we studied the roles of the dorsal (DR) and median raphe region (MRR) in aggression by optogenetically stimulating the two nuclei. Mice received three 3 min-long stimulations, which were separated by non-stimulation periods of 3 min. The stimulation of the MRR decreased aggression in a phasic-like manner. Effects were rapidly expressed during stimulations, and vanished similarly fast when stimulations were halted. No carryover effects were observed in the subsequent three trials performed at 2-day intervals. No effects on social behaviors were observed. By contrast, DR stimulation rapidly and tonically promoted social behaviors: effects were present during both the stimulation and non-stimulation periods of intermittent stimulations. Aggressive behaviors were marginally diminished by acute DR stimulations, but repeated stimulations administered over 8 days considerably decreased aggression even in the absence of concurrent stimulations, indicating the emergence of carryover effects. No such effects were observed in the case of social behaviors. We also investigated stimulation-induced neurotransmitter release in the prefrontal cortex, a major site of aggression control. MRR stimulation rapidly but transiently increased serotonin release, and induced a lasting increase in glutamate levels. DR stimulation had no effect on glutamate, but elicited a lasting increase of serotonin release. Prefrontal serotonin levels remained elevated for at least 2 h subsequent to DR stimulations. The stimulation of both nuclei increased GABA release rapidly and transiently. Thus, differential behavioral effects of the two raphe nuclei were associated with differences in their neurotransmission profiles. These findings reveal a surprisingly strong behavioral task division between the two raphe nuclei, which was associated with a nucleus-specific neurotransmitter release in the prefrontal cortex.

The Dorsal Raphe Regulates the Duration of Attack through the Medial Orbitofrontal Cortex and Medial Amygdala

“…The DR modulates attack behavior during aggressive encounters in rodents ( Chen et al, 1994 ; Takahashi et al, 2010 , 2015 ; da Veiga et al, 2011 ; Adachi et al, 2017 ; Balázsfi et al, 2018 ; Muroi and Ishii, 2019 ). The DR contains a heterogenous population of neurons that project to various brain regions to control social behavior and emotion ( Challis et al, 2013 ; Qi et al, 2014 ; Matthews et al, 2016 ; Ren et al, 2018 ; Huang et al, 2019 ).…”

Identification of Imaging and Clinical Markers Predicting Chronic Sleep Disturbances After Traumatic Brain Injury in Adults

“…In EDS, aggression is prevalent. Based on evidence, the dorsal raphe nucleus located in the brain stem has serotonergic transmission in the projections areas of prefrontal cortex, a main aggression control site [50], that plays an important role in the management of aggressive behaviors, and a lesion occurring in this nucleus causes antisocial behaviors [51]. Therefore, in patients with EDS, who mainly have brain stem lesions, damages of dorsal raphe nucleus or its serotonergic projections may take part in the occurrence of aggressive behaviors.…”

Optimization and validation of online column-switching assisted HPLC-spectrometric method for quantification of dansylated endocannabinoids and neurotransmitters in animal models of brain diseases

“…Dialysate sample were diluted and one part (240μl) was used for monoamines measurement as described in [35] and the left, 50μl was dansylated and used for amino acid analysis. The experimental results were published in the following journals [40,41].…”