The ethics of research involving animals - Nuffield Council on ...
The ethics of research involving animals - Nuffield Council on ...
The ethics of research involving animals - Nuffield Council on ...
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T h e e t h i c s o f r e s e a r c h i n v o l v i n g a n i m a l s<br />
escape from and avoid damage to their bodies have reflective c<strong>on</strong>sciousness.’ 11 We now<br />
discuss in more detail significant biological differences between humans and <str<strong>on</strong>g>animals</str<strong>on</strong>g>, and<br />
differences between kinds <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>animals</str<strong>on</strong>g>. We focus <strong>on</strong> physiological and neurological<br />
development, and describe their importance for welfare assessments.<br />
Pain, suffering and distress: meaning and functi<strong>on</strong> in <str<strong>on</strong>g>animals</str<strong>on</strong>g> and humans<br />
<str<strong>on</strong>g>The</str<strong>on</strong>g> basic evoluti<strong>on</strong>ary functi<strong>on</strong>s <str<strong>on</strong>g>of</str<strong>on</strong>g> pain and ways <str<strong>on</strong>g>of</str<strong>on</strong>g> relieving it<br />
4.11 In evoluti<strong>on</strong>ary terms, pain has evolved from nocicepti<strong>on</strong> as an aversive sensory mechanism<br />
that warns <str<strong>on</strong>g>of</str<strong>on</strong>g> harmful experiences. Pain has three main functi<strong>on</strong>s: First, it allows <str<strong>on</strong>g>animals</str<strong>on</strong>g> and<br />
humans to avoid dangerous situati<strong>on</strong>s, as painful experiences usually prompt an immediate<br />
impulse to withdraw and escape from situati<strong>on</strong>s that cause harm, usually in the form <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
tissue damage. Sec<strong>on</strong>dly, as pain is associated closely with the envir<strong>on</strong>mental c<strong>on</strong>text in<br />
which it occurred, its experience can help to prevent repeated damage. Pain-causing<br />
experiences will be avoided through learning when a similar envir<strong>on</strong>ment is encountered<br />
again. Thirdly, pain promotes the healing <str<strong>on</strong>g>of</str<strong>on</strong>g> injuries, as affected body parts are not used in<br />
normal activities, as far as possible.<br />
4.12 In the natural envir<strong>on</strong>ment where there are predators, and competiti<strong>on</strong> for mates and food,<br />
an overt display <str<strong>on</strong>g>of</str<strong>on</strong>g> pain-related behaviour could be disadvantageous. For example, an<br />
animal showing obvious signs <str<strong>on</strong>g>of</str<strong>on</strong>g> pain such as lameness or pain-related vocalisati<strong>on</strong> could<br />
become a target for predati<strong>on</strong> or aggressi<strong>on</strong> which would reduce its chances <str<strong>on</strong>g>of</str<strong>on</strong>g> mating or<br />
survival. Due to evoluti<strong>on</strong>ary pressures, many <str<strong>on</strong>g>animals</str<strong>on</strong>g> have therefore developed mechanisms<br />
that suppress signs <str<strong>on</strong>g>of</str<strong>on</strong>g> acute and chr<strong>on</strong>ic pain resulting, perhaps, from injury or an attack.<br />
Animals, including humans, produce opioids (natural ‘painkillers’) which may remain<br />
effective for a few minutes or several hours. 12 <str<strong>on</strong>g>The</str<strong>on</strong>g>se internally secreted opioids are released<br />
when chr<strong>on</strong>ic pain increases. This occurs through higher levels <str<strong>on</strong>g>of</str<strong>on</strong>g> activity <str<strong>on</strong>g>of</str<strong>on</strong>g> the ascending<br />
chr<strong>on</strong>ic pain pathways <str<strong>on</strong>g>of</str<strong>on</strong>g> humans and other <str<strong>on</strong>g>animals</str<strong>on</strong>g> (Figure 4.1). <str<strong>on</strong>g>The</str<strong>on</strong>g>y trigger painsuppressive<br />
pathways (known as descending pathways) which originate in the brain stem.<br />
This knowledge has been used to develop means for the alleviati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> pain in <str<strong>on</strong>g>animals</str<strong>on</strong>g> and<br />
humans by administering the opiate morphine, which acts <strong>on</strong> the same receptors. <str<strong>on</strong>g>The</str<strong>on</strong>g><br />
sensati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> pain can sometimes be partly or completely blocked by these natural<br />
endogenous pain relieving chemicals which are a physiological resp<strong>on</strong>se to injury.<br />
4.13 It is also important to note that the capacity for, and nature <str<strong>on</strong>g>of</str<strong>on</strong>g>, suffering probably depends<br />
<strong>on</strong> specific selecti<strong>on</strong> pressures which have acted <strong>on</strong> different species, favouring certain brain<br />
structures and functi<strong>on</strong>s over others. This phenomen<strong>on</strong> can be illustrated by c<strong>on</strong>sidering the<br />
loss <str<strong>on</strong>g>of</str<strong>on</strong>g> an <str<strong>on</strong>g>of</str<strong>on</strong>g>fspring. In humans, the suffering and distress from the loss <str<strong>on</strong>g>of</str<strong>on</strong>g> a child is<br />
emoti<strong>on</strong>ally devastating and debilitating, feelings that may persist for many years, even<br />
throughout life. Other species show signs that indicate severe distress at the loss <str<strong>on</strong>g>of</str<strong>on</strong>g> an infant,<br />
such as carrying the body around for several days. 13 Rodents, which mate more frequently<br />
and produce larger litters, do not display similar behaviours. Even if a whole litter <str<strong>on</strong>g>of</str<strong>on</strong>g> infants<br />
is removed, they return within hours to oestrus and mate again.<br />
11 Bates<strong>on</strong> P (1991) Assessment <str<strong>on</strong>g>of</str<strong>on</strong>g> pain in <str<strong>on</strong>g>animals</str<strong>on</strong>g> Anim Behav 42: 827–39.<br />
12 Lohmann AB and Welch SP (1999) ATP-gated K+ channel openers enhance opioid antinocicepti<strong>on</strong>: indirect evidence for the<br />
release <str<strong>on</strong>g>of</str<strong>on</strong>g> endogenous opioid peptides Eur J Pharmacol 385: 119–27.<br />
13 Some <str<strong>on</strong>g>animals</str<strong>on</strong>g> display the characteristic behaviour we associate with grief, such as withdrawal from the group or loss <str<strong>on</strong>g>of</str<strong>on</strong>g><br />
appetite. For example, sea li<strong>on</strong> mothers, watching their infants being eaten by killer whales, squeal and wail. Some <str<strong>on</strong>g>animals</str<strong>on</strong>g><br />
try to revive the corpse or carry it around until it decomposes. Primatologist Jane Goodall observed an eight year old male<br />
chimpanzee withdraw from its group, stop feeding and eventually die following the death <str<strong>on</strong>g>of</str<strong>on</strong>g> his mother. See Bek<str<strong>on</strong>g>of</str<strong>on</strong>g>f M<br />
(2000) Beastly passi<strong>on</strong>s New Scientist 29 April.<br />
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