Alcohol use and the pain system

Abstract

The World Health Organization's epidemiological data from 2016 revealed that while 57% of the global population aged 15 years or older had abstained from drinking alcohol in the previous year, more than half of the population in the Americas, Europe, and Western Pacific consumed alcohol. The spectrum of alcohol use behavior is broad: low-risk use (sensible and in moderation), at-risk use (e.g., binge drinking), harmful use (misuse) and dependence (alcoholism; addiction; alcohol use disorder). The at-risk use and misuse of alcohol is associated with the transition to dependence, as well as many damaging health outcomes and preventable causes of premature death. Recent conceptualizations of alcohol dependence posit that the subjective experience of pain may be a significant contributing factor in the transition across the spectrum of alcohol use behavior. This narrative review summarizes the effects of alcohol at all levels of the pain system. The pain system includes nociceptors as sensory indicators of potentially dangerous stimuli and tissue damage (nociception), spinal circuits mediating defensive reflexes, and most importantly, the supraspinal circuits mediating nocifensive behaviors and the perception of pain. Although the functional importance of pain is to protect from injury and further or future damage, chronic pain may emerge despite the recovery from, and absence of, biological damage (i.e., in the absence of nociception). Like other biological perceptual systems, pain is a construction contingent on sensory information and a history of individual experiences (i.e., learning and memory). Neuroadaptations and brain plasticity underlying learning and memory and other basic physiological functions can also result in pathological conditions such as chronic pain and addiction. Moreover, the negative affective/emotional aspect of pain perception provides embodied and motivational components that may play a substantial role in the transition from alcohol use to dependence.

Keywords: alcohol misuse; c-FOS; hyperkatifeia; neuroimmune interaction; nociception; pain pathways; pain-associated alcohol dependence.

FIGURE 1

Representative components of the pain system identified in the narrative review and the 3 dimensions of physical and psychological pain [55]. Abbreviations: PAG, periaqueductal Gray; PB, parabrachial nucleus; EWcp, centrally-projecting Edinger-Westphal nucleus; NTS, nucleus of the solitary tract; LC, locus coeruleus; BBB, blood brain barrier; IC, insular cortex; PVN, hypothalamic paraventricular nucleus; BNST, bed nucleus of the stria terminalis; central (CeA) and medial (MeA) nucleus of the amygdala; NA, nucleus accumbens; VTA, ventral tegmental area; mPFC, medial prefrontal cortex; ACC, anterior cingulate cortex.