Role of Enteric Glia as Bridging Element between Gut Inflammation and Visceral Pain Consolidation during Acute Colitis in Rats

Acute inflammation is particularly relevant in the pathogenesis of visceral hypersensitivity associated with inflammatory bowel diseases. Glia within the enteric nervous system, as well as within the central nervous system, contributes to neuroplasticity during inflammation, but whether enteric glia has the potential to modify visceral sensitivity following colitis is still unknown. This work aimed to investigate the occurrence of changes in the neuron–glial networks controlling visceral perception along the gut–brain axis during colitis, and to assess the effects of peripheral glial manipulation. Enteric glia activity was altered by the poison fluorocitrate (FC; 10 µmol kg−1 i.p.) before inducing colitis in animals (2,4-dinitrobenzenesulfonic acid, DNBS; 30 mg in 0.25 mL EtOH 50%), and visceral sensitivity, colon damage, and glia activation along the pain pathway were studied. FC injection significantly reduced the visceral hyperalgesia, the histological damage, and the immune activation caused by DNBS. Intestinal inflammation is associated with a parallel overexpression of TRPV1 and S100β along the gut–brain axis (colonic myenteric plexuses, dorsal root ganglion, and periaqueductal grey area). This effect was prevented by FC. Peripheral glia activity modulation emerges as a promising strategy for counteracting visceral pain induced by colitis.

Biopsychosocial intersections of social/affective touch and psychiatry: Implications of ‘touch hunger’ during COVID-19

Background: Humans are neurobiologically wired for touch receptivity. Social touch is a common and mutual way of expressing affection, care, and intimacy. From an evolutionary perspective, affiliative and affectionate touch are considered necessary for social and cognitive development throughout life-stages and across species. The emergence of the COVID-19 pandemic as a public health threat has mandated social distancing as a measure to contain the global outbreak. Travel restrictions, lockdown, and quarantine have led to separation and segregation, giving rise to social touch deprivation that might have adverse biopsychosocial consequences. Methods: Affective touch has rarely been discussed within the purview of social psychiatry. We attempted to review the neurobiological, social, and behavioural correlates of social and sexual touch, as well as the neurophysiological models involved. Results: The unmyelinated peripheral C-fibre afferents projecting to insular cortex and somatosensory areas form the prime pathway for affective touch. ‘Top-down’ modulation via the periaqueductal grey area, rostroventral medulla and sub-cortical structures, and ‘Bottom-up’ approach via the dorsal horn of the spine form the two theoretical models of ‘social touch’ system. The mu - opioid receptor (MOR) implicated in the Brain Opioid Theory of Social Attachment (BOTSA) and social neuropeptides like oxytocin and vasopressin are the primary neurochemical substrates involved. Sexual intimacy involves other neurotransmitters, with increased oxytocin activity in the limbic structures, Nucleus Accumbens, Anterior Cingulate, and Prefrontal Cortex. The discrimination and amalgamation of touch senses, their affiliative value and emotional valence in humans are based on a complex interplay between psychobiological, environmental, and personal factors. Conclusion: The neurobehavioral and emotional effects of ‘touch hunger’ and strategies to mitigate it during COVID-19 are discussed in the context of psychoneuroimmunity and stress.

The effect of 5-HT2a/2c receptor agonist microinjected into central amygdaloid nucleus and median preoptic area on maternal aggressive behavior in rats

OBJECTIVE: Much evidence supports the hypothesis that 5-hydroxytryptamine (5-HT) activation is related to the inhibition of aggression. We examined potentially pro- and anti-aggressive effects of the 5-HT2A/2C receptor agonist on specific brain sites. METHOD: Female Wistar rats on the 7th day postpartum were microinjected with the selective 5-HT2A/2C receptor agonist, alpha-methyl-5-hydroxytryptamine maleate (0.2 to 1.0 µg/0.2 µl) into the central amygdaloid nucleus and median preoptic nucleus. For each brain area studied, the frequency of the behaviors: locomotion, social investigation, lateral threat, attacks (frontal and lateral), and biting the intruder were compared among the various treatments by an Analysis of Variance, followed when appropriate, by Tukey's test. RESULTS: Microinjection of the selective 5-HT2A/2C receptor agonist, a-methyl-5-hydroxytryptamine maleate into central amygdaloid nucleus increased maternal aggression in the absence of concurrent changes in non-aggressive behavior. By contrast, microinjection of the selective 5-HT2A/2C receptor agonist at several dilutions into the median preoptic nucleusdid not alter aggressive behavior. CONCLUSIONS: The current and earlier data with pro- and anti-aggressive effects of the 5-HT2a/2c receptor agonist, when microinjected into the median preoptic nucleus relative to the central amygdaloid nucleus, medial septum and periaqueductal grey area in female rats point to functionally separate serotonin receptor populations in the amygdaloid-septal-hypothalamic and periaqueductal gray matter areas controlling aggressive behavior. It is possible that amygdaloid 5-HT2a/2c receptors may increase aggressive behavior in lactating females as a result of changes in fear.