Visceral pain in humans: Lessons from animals

Abstract

Acute and persistent neuropathic and inflammatory injuries of healthy animals have contributed importantly to our current understanding of nociception and pain. Studies have differentiated somatic from visceral nociceptive input, and elucidated the pathways of transduction, transmission, perception, and modulation of the input. Other animal studies have identified important genetic and environmental influences on responses to nociception. Studies of naturally occurring visceral pain syndromes in animals also have added to our understanding of comparable syndromes in humans. Because of the aversive nature of pain, use of healthy animals to study pain in the service of other animals and humans is a decision to be taken carefully, and carries with it the responsibility of treating the animals as humanely as possible.

Evaluation of the effects of stress in cats with idiopathic cystitis

“…An increase in SNS outflow activity could also explain why clinical signs of FIC follow a waxing and waning course in cats and humans and are aggravated by environmental stressors. 28,29 Amitriptyline and other tricyclic antidepressant drugs with sympatholytic activity have been used to ameliorate the severity of the chronic form of the disease in both species. 30,31 The present study had several limitations concerning plasma fluorescein concentrations and catecholamine analyses.…”

Experimental oesophagitis in the rat is associated with decreased voluntary movement

“…The reasons for the lack of full understanding of this mechanism include its complexity, and the obstacle to experimental approaches presented by the difficulty of evaluating symptoms in laboratory animals. To be sure, there has been a comparatively large amount of research evaluating the severity of somatic pain in animals, 7,8 and evaluation of expanding visceral pain by electromyography has also been reported, specifically electromyography of the abdominal wall muscles for pain evoked by rectal distension 9,10 and electromyography of the ventral pectoral muscles and acromiotrapezius muscles for pain evoked by gastric distension 11,12 . However, the electromyographic changes in those voluntary muscles reflect the body’s response to severe, acute distension‐induced pain; 12,13 to date, there has been no research evaluating in animals the kind of dull, diffuse, persistent visceral pain observed clinically in human patients, and there has been no experimental method providing an index for the evaluation of such pain.…”

Animal models of chronic pain. Are naturally occurring diseases a potential model for translational research?

“…Nonetheless, scientific evidence discussing how these conditions could represent a translational approach has only been reported for feline interstitial cystitis (Buffington 2001), feline diabetes mellitus (Mizisin et al 2002), osteoarthritis (McCoy 2015) and various tumours in dogs (Peña et al 2003, Brown et al 2009 and cats (Pérez-Alenza et al 2004), lameness in dairy cattle and horses (Bustamante et al 2015, Rodriguez et al 2018, Herzberg et al 2019, tail docking in dairy cows (Troncoso et al 2018). According to Klinck et al (2017), this relatively limited evidence could be indicative of the complexity in the design and interpretation of studies in which the number of recruited subjects is reduced.…”