Prozac and Sarafem\u00a0are brand names for a drug called “fluoxetine<\/a>,” which was first discovered by Eli Lilly in 1972. Since the patent for this drug expired in 2001, fluoxetine is available as a generic FDA-approved prescription for\u00a0depression<\/a>,\u00a0obsessive-compulsive disorder<\/a>,\u00a0panic attacks<\/a>, and some\u00a0eating disorders<\/a>.<\/p>\n Source: metamorworks\/Shutterstock<\/p><\/div>\n Historically, most experts and consumers thought fluoxetine worked by inhibiting the reuptake of serotonin in the brain, and that the antidepressant effects of this drug occurred solely from the “neck up.” However, there is still a surprising amount of uncertainty about how SSRIs actually work.<\/p>\n Because 90 percent of the human body’s serotonin is produced in the gut, one current theory is that fluoxetine might boost the amount of serotonin produced “below the neck.”<\/p>\n While the 21st-century debate about SSRIs rages on, a drug-free alternative for treatment-resistant depression called “vagus nerve stimulation<\/a>\u00a0(VNS)” was approved by the FDA in 2005 for severe unipolar and\u00a0bipolar<\/a>\u00a0depression. VNS typically involves a small, silver-dollar sized device that is surgically implanted below the skin near the collar bone and works like a pacemaker to stimulate the vagus nerve.<\/p>\n Source: Alila Medical Media\/Shutterstock<\/p><\/div>\n<\/div>\n<\/div>\n In recent years, researchers at\u00a0McMaster University’s Brain-Body Institute<\/a>\u00a0(Canada) have been investigating a possible link between SSRI antidepressant medications, serotonin levels in the gut, and the role that vagus nerve stimulation might play in boosting gut-to-brain transport of serotonin, which appears to rely on the vagus nerve.<\/p>\n Notably, after a vagotomy\u2014which surgically cuts off gut-to-brain communication via the vagus nerve\u2014SSRIs lose their ability to relieve depression-like symptoms in mice.<\/p>\n As part of the bidirectional gut-brain axis, afferent\u00a0vagal<\/a>\u00a0nerves send signals from the bottom-up. There is reason to believe that these vagus nerve pathways might serve as a type of “serotonin superhighway” between the gut and the brain.<\/p>\n A few days ago, the\u00a0team at McMaster University\u2014who’ve\u00a0been conducting research in mice about how SSRIs and the vagus nerve might work in tandem\u2014published a study, “Oral Selective Serotonin Reuptake Inhibitors Activate Vagus Nerve Dependent Gut-Brain Signalling,<\/a>” in the journal\u00a0Scientific Reports. The title of this paper sums up the main takeaway of this research: SSRIs may activate the vagus nerve in a way that facilitates gut-brain serotonin signaling.<\/p>\n The authors (McVey Neufeld et al., 2019) describe the context and significance of their findings:<\/p>\n “The vagus nerve is the tenth cranial nerve and is the main afferent pathway connecting the gut to the brain. The vagus nerve can transmit signals to the brain resulting in a reduction in depressive behavior as evidenced by the long-term beneficial effects of electrical stimulation of the vagus in patients with intractable depression.<\/p>\n The vagus\u00a0is the major\u00a0neural<\/a>\u00a0connection between gut and brain, and we have previously shown that ingestion of beneficial bacteria modulates behaviour and brain neurochemistry via this pathway. Given the high levels of serotonin in the gut, we considered if gut-brain signaling, and specifically the vagal pathway, might contribute to the therapeutic effect of oral selective serotonin reuptake inhibitors (SSRI).”<\/p><\/blockquote>\n In a recent\u00a0interview<\/a>\u00a0with Canadian Press\u00a0published on October 4, 2019, first author\u00a0Karen-Anne McVey Neufeld said, “This [research] opens the door for examining the gut and the continuous communication that happens between the gut and the brain.”\u00a0She also said that her team’s findings “suggest the gut may play a larger role in depression than previously believed and the latest research hints at new treatment possibilities in the future.”<\/p>\n Interestingly, McVey Neufeld also told the Canadian Press reporter\u00a0that another class of antidepressants called “noradrenaline reuptake inhibitors (NRIs)” did not appear to have the same activating effect on the vagus nerve as SSRIs.<\/p>\n “Our results lend weight to the possibility that the vagal pathway connecting gut to brain may provide a novel opportunity for treatment of some\u00a0psychiatric<\/a>\u00a0disorders,” the authors write in the paper’s conclusion. “While further study is both necessary and ongoing, we believe that these findings may point towards a newly invigorated approach in the continuing search for new\u00a0drugs<\/a>, dietary supplements or bacteria to beneficially modulate these conditions through their effects on vagal afferent communication.”<\/p>\n The next step for McVey Neufeld and colleagues at McMaster’s Brain-Body Institute is to identify specific gut microbiome factors that may play into mental health and psychological well-being using vagus nerve gut-to-brain signaling.<\/p>\n If a picture is worth a thousand words, this\u00a0early anatomical drawing of the vagus nerve (below) speaks volumes. As you scroll down this narrow-and-long image, try visualizing how your vagus nerve facilitates communication along your gut-brain axis as part of a bidirectional feedback loop.<\/p>\n Early anatomical drawing of the “wandering” vagus nerve. Source: Wellcome Library\/Public Domain<\/p><\/div>\n<\/div>\n The vagus nerve is also called the “wandering nerve” because it’s the longest nerve in the human body and has countless branches that wind their way from the brainstem all the way down to the lowest part of the intestines, touching most major organs along the way. The vagus nerve modulates the parasympathetic nervous system, which counterbalances the fight-or-flight\u00a0stress<\/a>\u00a0response by eliciting the so-called “relaxation response.”<\/p>\n Over the years, I’ve written dozens of\u00a0Psychology Today\u00a0blog posts about the vagus nerve. In 2017, I wrote a 9-part series, “The Vagus Nerve Survival Guide to Combat Fight-or-Flight Urges<\/a>.” Earlier this year, I wrote a widely-read post, “Longer Exhalations Are an Easy Way to Hack the Vagus Nerve<\/a>.”<\/p>\n Every time you exhale, your\u00a0vagus nerve squirts some acetylcholine (also known as “vagusstoff” or “vagus substance”) onto your\u00a0heart. Vagusstoff acts as a tranquilizer-like substance to slow\u00a0down beat-to-beat intervals and improves\u00a0heart rate variability (HRV)<\/a>.\u00a0Robust\u00a0vagal tone and higher HRV go hand in hand and are markers for overall psychological and physical well-being.<\/p>\n LinkedIn Image Credit: fizkes\/Shutterstock<\/p>\n<\/div>\n References<\/p>\n Karen-Anne McVey Neufeld, John Bienenstock, Aadil Bharwani, Kevin Champagne-Jorgensen, YuKang Mao, Christine West, Yunpeng Liu, Michael G. Surette, Wolfgang Kunze & Paul Forsythe. “Oral Selective Serotonin Reuptake Inhibitors Activate Vagus Nerve Dependent Gut-Brain Signalling.”\u00a0Scientific Reports\u00a0(First published: October 3, 2019) DOI:\u00a010.1038\/s41598-019-50807-8<\/a><\/p>\n![\"\"](\"https:\/\/opa-old.voidappsdev.uk\/wp-content\/uploads\/2021\/01\/metamorworks_shutterstock_gut-brain-axis_vagus_nerve1-300x300.jpg\")
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Why\u00a0Is the Vagus Nerve Also Called the Wandering Nerve?<\/h3>\n
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