Biology subjects

Ng, A. J.

Publications and source records attributed to Ng, A. J..

5 recordsLinked to original sources

bioRxiv2023

Melanin concentrating hormone and orexin shape social affective behavior via action in the insular cortex

RationaleIn a social context, individuals are able to detect external information from others and coordinate behavioral responses according to the situation, a phenomenon called social decision-making. Social decision-making is multifaceted, influenced by emotional and motivational factors like stress, sickness and hunger. However, the neurobiological basis for motivational state competition and interaction are not well known. ObjectiveWe investigated possible neural mechanisms through which internal states could shape social behavior in a social affective preference (SAP) test. In the SAP test, experimental rats given a choice to interact with naive or stressed conspecifics exhibit an age-dependent preference to interact with stressed juvenile conspecifics, but avoid stressed adult conspecifics. First, we assessed the effect of hunger on SAP behavior. Behavior in the SAP test requires the insular cortex, which receives input from the hunger-related peptides melanin-concentrating hormone (MCH) and orexin neurons of the lateral hypothalamus (LH). This study aimed to evaluate the role of LH and insular MCH and orexin in SAP test. MethodsSAP tests were conducted in rats that were sated, food deprived or allowed 1 h of access to food after 14 h of deprivation (relieved condition). Separate cohorts of sated rats received cannula implants for microinjection of drugs to inhibit the LH or to block or stimulate MCH or orexin receptors in the insula prior to SAP tests or social interaction tests. ResultsFood and water deprivation prior to SAP tests with juvenile rats caused a shift in preference away from the stressed rat toward the naive juveniles. Pharmacological inhibition of LH with muscimol (100 ng/side) abolished the preference for the juvenile stressed conspecific, as well as the preference for the adult naive conspecific. The blockade of MCHr1 or orexin receptors in the insular cortex with SNAP94847 (50{micro}M) or TCS1102 (1{micro}M), respectively, also abolished the preference for the stressed juvenile conspecific, but only the antagonism of orexin receptors was able to abolish the preference for the adult naive conspecific. Microinjection of increasing doses (50 or 500 nM) of MCH or orexin-A in the insular cortex increased the interaction time in the one-on-one social interactions test with juvenile conspecifics, however only the microinjection of orexin-A increased the interaction time with adult naive conspecifics. ConclusionsTaken together, these results suggest that lateral hypothalamus peptides shape the direction of social approach or avoidance via actions MCH and orexin neurotransmission in the insular cortex.

neuroscience↗

bioRxiv2023

Serotonin modulates social responses to stressed conspecifics via insular 5-HT2C receptors in rat

Social interaction allows for the transfer of affective states among individuals, and the behaviors and expressions associated with pain and fear can evoke anxiety-like states in observers which shape subsequent social interactions. We hypothesized that social reactions to stressed individuals engage the serotonergic dorsal raphe nucleus (DRN) which promotes anxiety-like behavior via postsynaptic action of serotonin at serotonin 2C (5-HT2C) receptors in the forebrain. First, we inhibited the DRN by administering an agonist (8-OH-DPAT, 1{micro}g in 0.5{micro}L) for the inhibitory 5-HT1A autoreceptors which silences 5-HT neuronal activity via G-protein coupled inward rectifying potassium channels. 8-OH-DPAT prevented the approach and avoidance, respectively, of stressed juvenile (PN30) or stressed adult (PN60) conspecifics in the social affective preference (SAP) test in rats. Similarly, systemic administration of a 5-HT2C receptor antagonist (SB242084, 1mg/kg, i.p.) prevented approach and avoidance of stressed juvenile or adult conspecifics, respectively. Seeking a locus of 5-HT2C action, we considered the posterior insular cortex which is critical for social affective behaviors and rich with 5-HT2C receptors. SB242084 administered directly into the insular cortex (5{micro}M in 0.5{micro}L bilaterally) interfered with the typical approach and avoidance behaviors observed in the SAP test. Finally, using fluorescent in situ hybridization, we found that 5-HT2C receptor mRNA (htr2c) is primarily colocalized with mRNA associated with excitatory glutamatergic neurons (vglut1) in the posterior insula. Importantly, the results of these treatments were the same in male and female rats. These data suggest that interactions with stressed others require the serotonergic DRN and that serotonin modulates social affective decision-making via action at insular 5-HT2C receptors.

neuroscience↗

bioRxiv2023

Social affective behaviors among female rats involve the basolateral amygdala and insular cortex

The ability to detect, appraise, and respond to anothers emotional state is essential to social affective behavior. This is mediated by a network of brain regions responsible for integrating external cues with internal states to orchestrate situationally appropriate behavioral responses. The basolateral amygdala (BLA) and the insular cortex are reciprocally connected regions involved in social cognition and prior work in male rats revealed their contributions to social affective behavior. We investigated the functional role of these regions in female rats in a social affective preference (SAP) test in which experimental rats approach stressed juvenile but avoid stressed adult conspecifics. In separate experiments, the BLA or the insula were inhibited by local infusion of muscimol (100ng/side in 0.5L saline) or vehicle prior to SAP tests. In both regions, muscimol interfered with preference for the stressed juvenile and naive adult, indicating that these regions are necessary for appropriate social affective behavior. In male rats, SAP behavior requires insular oxytocin but there are noteworthy sex differences in the oxytocin receptor distribution in rats. Oxytocin (500nM) administered to the insula did not alter social behavior but oxytocin infusions to the BLA increased social interaction. In sum, female rats appear to use the same BLA and insula regions for social affective behavior but sex differences exist in contribution of oxytocin in the insula.

neuroscience↗

bioRxiv2022

Maternal immune activation alters social affective behavior and sensitivity to corticotropin releasing factor in male but not female rats

Prenatal infection increases risk for neurodevelopmental disorders such as autism in offspring. In the rodents, prenatal administration of the viral mimic Polyinosinic:polycytidylic acid (Poly I:C) allows for investigation of developmental consequences of gestational sickness on offspring social behavior and neural circuit function. Because maternal immune activation (MIA) disrupts cortical development and sociability, we examined social decision-making in a rat social affective preference (SAP) task. Following Poly I:C (0.5 mg/kg) on gestational day 12.5, male adult offspring (PN 50) exhibited atypical social interactions with stressed conspecifics whereas female SAP behavior was unaffected by maternal Poly I:C. Social responses to stressed conspecifics depend upon the insular cortex where corticotropin releasing factor (CRF) modulates synaptic transmission and SAP behavior. We characterized insular field excitatory postsynaptic potentials (fEPSP) in adult offspring of MIA or control treated dams. Male MIA offspring showed decreased sensitivity to CRF (300 nM) while female MIA offspring showed greater sensitivity to CRF compared to sham offspring. These sex specific effects appear to be behaviorally relevant as CRF injected into the insula of male and female rats prior to social exploration testing had no effect in MIA male offspring but increased social interaction in female MIA offspring. We examined the cellular distribution of CRF receptor mRNA but found no effect of maternal Poly I:C in the insula. Together these experiments reveal sex specific effects of prenatal infection on offspring social decision making and identify insular CRF signaling as a novel neurobiological substrate for autism risk.

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bioRxiv2021

Insular cortex corticotropin-releasing factor integrates stress signaling with social decision making.

Impairments in social cognition manifest in a variety of psychiatric disorders, making the neurobiological mechanisms underlying social decision making of particular translational importance. The insular cortex is consistently implicated in stress-related social and anxiety disorders, which are associated with diminished ability to make and use inferences about the emotions of others to guide behavior. We investigated how corticotropin releasing factor (CRF), a neuromodulator evoked by both self and social stressors, influenced the insula. In acute slices from male and female rats, CRF depolarized insular pyramidal neurons. In males, but not females, CRF suppressed presynaptic GABAergic inhibition leading to greater excitatory synaptic efficacy in a CRF receptor 1 (CRF1) and cannabinoid receptor 1 (CB1) dependent fashion. In males only, insular CRF increased social investigation, and CRF1 and CB1 antagonists interfered with social decision making. To investigate the molecular and cellular basis for the effect of CRF we examined insular CRF1 and CB1 mRNAs and found greater total insula CRF1 mRNA in females but greater CRF1 and CB1 mRNA colocalization in male insular cortex glutamatergic neurons which suggest complex, sex-specific organization of CRF and endocannabinoid systems. Together these results reveal a new sex-specific mechanism by which stress and affect contribute to social decision making.

neuroscience↗