Perception of pain in animals

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According to Manfred Zimmermann, an aversive sensory experience can be described as pain perception in animals ,

"Which is triggered by actual or threatened injury, evokes motor and vegetative protective reactions, leads to learned avoidance and possibly changes species-specific behavior, including social behavior ."

- carpenter :

This definition follows that for the perception of pain in humans, which is described by the International Society for the Study of Pain (IASP) as “an unpleasant sensory and emotional experience associated with, or in terms of, actual or threatened tissue damage Damage is described. ” However, it is not possible to find out whether animals also experience such a feeling . Therefore the reference to emotional experiences is usually excluded in the definitions of pain perception in animals.

The standard measure of pain in a person is his own statement, because only he knows the quality and intensity of the pain and the degree of suffering. Animals without the ability to speak cannot communicate their condition. Whether they are aware and able to suffer has been the subject of much debate after students were taught until the 1980s that animals would feel no pain.

There are two crucial components to pain: the sensory component ( nociceptor ) and the aversive, negative affective state. The nociceptor enables the detection of harmful stimuli and the subsequent knee-jerk reaction to move all or part of the body away from the source of the stimulus. This property can be observed in all large taxa . Nociception can be observed using modern imaging techniques and a physiological and behavioral response to nociception can be demonstrated. However, there is currently no objective measure of suffering.

history

The idea that animals may not experience pain or suffering like humans do goes back at least to 17th century France. The French philosopher René Descartes assumed that animals had a lack of consciousness.

As recently as the 1980s, researchers were unsure whether animals could feel pain. Veterinarians trained in the US were taught before 1989 that animals cannot feel pain. During his discussions with fellow scientists and veterinarians, Bernard Rollin ( Colorado State University ) was regularly asked to prove that animals are conscious and provide " scientifically acceptable " grounds for claiming that animals have a sense of pain. Some authors believe that the claim that animals feel pain differently than humans is now a minority. Academic reviews on the subject are rather questionable, yet it is likely that some animals have at least simple conscious thoughts and feelings. A few authors continue to deal with the question of how reliably the well-being of animals can be determined.

Clues for feeling pain

The ability to perceive pain in animals cannot be determined directly. However, it can be derived from physiological and behavioral responses. Some signs that may indicate the presence of pain include:

Vertebrates

fishes

Research assumes that at least real bony fish have a pain sensation comparable to that of land vertebrates . These statements are, however, subject to general difficulties in making scientific statements about mental states in other animals and the perception of pain.

In addition to the legally recognized ability of fish to suffer, it is also recognized by the case law that fish actually have this ability. It is based on the sensory-physiological studies of fish that have been carried out for more than two decades and the unanimous opinion of specialist scientists.

behavior

Experiments have shown that frogfish grunted when exposed to electrical stimuli. Over time, when they saw an electrode, they grunted.

In 2003, after further research on rainbow trout , researchers at the University of Edinburgh concluded that fish often exhibit behavior associated with pain. Likewise, the fish's brains release neurotransmitters in the same way as humans do when pain is felt. Research has been criticized, however, that fish's reactions could also have other causes, especially from the point of view that their brains functioned differently and they may not have the same level of consciousness as humans.

A 2009 study from Norway concluded that goldfish can experience pain and that their reactions are similar to those of humans. The scientists argue that it is believed that the response of fish to a painful stimulus is a knee-jerk action, not a pain sensation. The focus of the research was therefore to find out whether fish only react reflexively or in a more sophisticated way to stimuli. One group of fish was given morphine and the other was given saline. They were then exposed to uncomfortable temperatures, with the fish reacting to saline with defensive behavior, which is interpreted as fear and increased alertness. The fish with morphine showed no reaction. The scientists concluded that fish responded to painful stimuli with both reflex and conscious pain.

anatomy

Nociception is the unconscious realization of the nervous system that there is pain somewhere in the body. Nociceptors are sensory receptors that respond to potentially damaging stimuli. To do this, they send signals to the spinal cord and brain via the nerves. In 2003, Lynne Sneddon of the University of Chester detected the presence of nociceptors in the face and mouth of trout .

Invertebrates

Although it has been suggested that most invertebrates do not experience pain, there is some evidence that invertebrates, especially crustaceans (e.g. crabs and lobsters ) and cephalopods (e.g. squid ), have behavioral and physiological responses in this way. This indicates that they may be capable of such a sensation. Nociceptors have been discovered in roundworms , annelids and mollusks . Most insects have no nociceptors; a well-known exception is the fruit fly . Vertebrates release endogenous opioids that interact with opiate receptors to relieve pain . Opioid peptides and opiate receptors are naturally found in roundworms, mollusks, insects and crustaceans. The presence of opioids in crustaceans has been interpreted as suggesting that lobsters may have the ability to experience pain, although it has been suggested that no conclusion can be drawn at this time.

One of the arguments for denying invertebrates to feel pain is that their brains are too small for that. However, the size of the brain does not necessarily correspond to the complexity. In addition, the cephalopod brain is just as large in relation to its brain mass to body weight as that of vertebrates, smaller than that of birds and mammals , but as large as or larger than that of most fish.

Crustaceans

The question of whether or not crustaceans can feel pain is not yet clear. One publication states that the opioids may suppress pain in lobsters in the same way as they do in vertebrates . Morphine injections into crabs reduced their response to electric shocks. This effect diminished with a smaller injection amount and greater time intervals between injection and stimulus. Lobsters also react less strongly to stimuli after the administration of painkillers.

Medicine and research

Veterinary medicine

In veterinary medicine, animals are given the same analgesics and anesthetics as humans when they experience actual or threatened pain.

Dolorimetry

Dolorimetry (dolor: Latin for pain) describes a measurement method for pain reactions in animals and humans. In medicine it is occasionally used for diagnosis, in research it is regularly used to research pain and the effectiveness of analgesics. Techniques for measuring pain in non-human animals include the Randall-Selitto test , the tail flick test and the hot plate test .

Laboratory animals

Animals are kept in laboratories for animal testing for a variety of reasons . In some cases, the animals are inflicted with pain, suffering or agony. In other cases (e.g. some related to breeding) not. The question of the extent and which experiments cause pain in laboratory animals has been the subject of much debate.

Marian Stamp Dawkins of the University of Oxford defines suffering in laboratory animals as an experience of "a wide range of extremely uncomfortable subjective (mental) conditions." The US Department of Agriculture defined "painful procedure" in a study of animals as a procedure that " likely to cause more than minor or transient pain or distress in a person who would undergo this procedure. ”A few critics argue that researchers who grew up in times of increased attention to animal welfare tend to experience a similar pain To deny animals. This is because they do not want to be seen as the ones who cause them the damage.

Load tables

In 2011 there were stress tables in eleven countries to classify the pain and suffering of animals in research: Australia, Canada, Finland, Germany, Ireland, the Netherlands, New Zealand, Poland, Sweden, Switzerland, and Great Britain. In the USA there is also such a classification system at the national level, but it differs markedly from the others in that it indicates whether pain relievers were needed and / or administered.

The first stress tables were introduced in Finland and Great Britain in 1986. The degree of pain is rated in categories between three (Sweden and Finland) and 9 (Australia). In Great Britain, research projects related to animal suffering are classified as mild (“mild”), moderate (“moderate”) and significant (“substantial”). Unclassified forms a fourth category and means that the animal has been anesthetized and killed without having regained consciousness.

The Charité hospital in Berlin has a detailed leaflet available for categorization. It divides animal suffering into four categories: no pollution , low pollution , moderate pollution, and significant pollution .

See also

Individual evidence

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  2. ↑ What actually is pain. Translation of the German Society for the Study of Pain. Retrieved February 29, 2012 .
  3. ↑ How do animals feel pain? ; Information on the program W wie Wissen from November 24, 2014
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  11. ^ FV Abbott, KB Franklin, RF Westbrook: The formalin test: scoring properties of the first and second phases of the pain response in rats . In: Pain . tape 60 , no. 1 , 1995, p. 91-102 , doi : 10.1016 / 0304-3959 (94) 00095-V ( The formalin test: scoring properties of the first and second phases of the pain response in rats ).
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    • KP Chandroo, IJH Duncan, RD Moccia: Can fish suffer ?: perspectives on sentience, pain, fear and stress . In: Applied Animal Behavior Science . 86, No. 3-4, 2004, pp. 225-250.
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  21. ↑ Purdue University: Fish may actually feel pain and react to it much like humans. 2009, accessed May 7, 2012 .
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  39. ↑ N. Zabala, M. Gomez: Morphine analgesia, tolerance and addiction in the cricket, Pteronemobius . In: Pharmacology, Biochemistry and Behavior . tape 40 , 1991, pp. 887-891 .
  40. ^ A b M. Lozada, A. Romano, H. Maldonado: Effect of morphine and naloxone on a defensive response of the crab Chasmagnathus granulatus . In: Pharmacology, Biochemistry and Behavior . tape 30 , 1988, pp. 635-640 .
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  42. ↑ a b L. Sømme: Sentience and pain in invertebrates: Report to Norwegian Scientific Committee for Food Safety . Ed .: Norwegian University of Life Sciences. Oslo 2005.
  43. ↑ a b Adcovates for Animals: Cephalopods and decapod crustaceans: Their capacity to experience pain and suffering . 2005 ( advocatesforanimals.org.uk (PDF)). advocatesforanimals.org.uk ( Memento of the original from April 6, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.advocatesforanimals.org.uk
  44. ↑ L. Chittka, J. Niven: Are Bigger Brains Better? In: Current Biology . tape 19 (21) , 2009, doi : 10.1016 / j.cub.2009.08.023 .
  45. ↑ Cephalopod brain size ( Memento of the original from November 18, 2011 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. accessed on February 29, 2012  @1@ 2Template: Webachiv / IABot / www.kheper.net
  46. ^ A. Packard: Abstract cephalopods and fish: The limits of convergence . In: Biological Reviews . tape 47 , p. 241-307 , doi : 10.1111 / j.1469-185X.1972.tb00975.x .
  47. ↑ European Food Safety Authority (Ed.): Aspects of the biology and welfare of animals used for experimental and other scientific purposes . doi : 10.2903 / j.efsa.2005.292 .
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  49. ^ IJ Duncan, JC Petherick: The implications of cognitive processes for animal welfare . In: J. Anim. Sci . tape 69 , no. 12 , 1991, pp. 5001-5007 , PMID 1808193 .
  50. ^ M. Stamp Dawkins: Scientific Basis for Assessing Suffering in Animals. In Peter Singer . In Defense of Animals: The Second Wave . Blackwell, 2006, pp. 28 .
  51. ^ Animal Welfare; Definitions for and Reporting of Pain and Distress. In: Animal Welfare Information Center Bulletin, Summer 2000, Vol. 11 No. 1-2. US Department of Agriculture, 2000, archived from the original on October 6, 2014 ; Retrieved March 1, 2012 .
  52. ^ Larry Carbone: What Animal Want: Expertise and Advocacy in Laboratory Animal Welfare Policy . Oxford University Press, 2004, pp. 151 .
  53. ^ N. Fenwick, E. Ormandy, C. Gauthier, G. Griffin: Classifying the severity of scientific animal use: a review of international systems. In: Animal Welfare . No. 20 , 2011, p. 281-301 .
  54. ↑ Orientation aid from the Berlin Animal Welfare Officer working group on the classification of exposure levels for animal experiments requiring approval. (PDF; 68 kB) (No longer available online.) Formerly in the original ; Retrieved March 2, 2012 .  ( Page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice. @1@ 2Template: Dead Link / www.charite.de  

Remarks

  1. ↑ Original definition : an aversive sensory experience caused by actual or potential injury that elicits protective motor and vegetative reactions, results in learned avoidance and may modify species-specific behavior, including social behavior.