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Campaign to end the docking of dogs' tails (and cropping of ears)


 image 1 image 2 image 3Dobes
Cocker Spaniel                                Pup                                      Rottweiler Pup                Dobermann docking circa 1988


 
Neonatal Pain and its effect on Adult Behaviour and Socialisation: a brief overview
Kindly submitted by (Animal Welfare Science Ethics and Law Association - AWSELVA).

1.          Introduction

Our understanding of pain control mechanisms in neonatal mammals has changed radically over the past twenty-five years.  This brief overview seeks to present a brief synopsis
of current understanding of neonatal pain with reference to the scientific studies on which it is based. 

2.    Descending Modulatory Control of Pain
The anatomical, physiological and neurological details of descending modulatory control of pain is well understood and has been described in detail by (Fields et al 1999) .  
In summary, the thalamus is the centre in the brain for perception of pain. Stimulation of specific sites in the brain has been consistently shown to produce analgesia in man;
this phenomenon is known as "stimulation produced analgesia".  The sites identified include the dorsolateral funiculus, the periaquaductal grey, the rostroventraomedial
medulla and the dorsolateral pontine tegument.   Large descending myelinated fibres have been identified in the spinal cord, which synapse with neurones from skin
nociceptive cells in the dorsal horn of the spinal cord and inhibit transmission of afferent pain-induced nerve impulses to the higher centres.


3.       Pain and Neonates
The developmental neurobiology of pain is summarised by [Fitzgerald, 1999 #750.  While there is little known about the emotional experience of pain in the neonate,
the nervous system of neonatal humans and rats shows mature nociceptive function, details of which have been described (Berde & Masek 1999)
 

3.1  Absence of descending modulatory control in neonates. 
It has been demonstrated in rats that there is delayed connection of inhibitory pathways to spinal nociceptive cells; no
electrophysiological evidence of inhibition has been found until postnatal day 10 and there is histological evidence that the descending inhibitory neurones are
still developing along the spinal cord.  In human infants the threshold for the cutaneous flexor reflex is low at birth and gradually increases with age.  Such reduced
pain thresholds have also been demonstrated in neonatal rat pups and kittens.   

3.2  Neonates have normal physiological, hormonal and behavioural responses to pain. 
Neonates have been shown to produce hormonal, physiological and behavioural stress responses, in response to pain, that are similar to those produced by adults,
however they occur at lower thresholds.  Such responses are reduced or diminished by the administration of analgesics in neonates
.   

3.3  Neonates are hypersensitive to pain: routine pain control protocols in neonatal infants. 
Thus, neonates are hypersensitive, rather than hyposensitive in comparison to an adult animal.   The assessment and control of pain in neonatal infants is well
developed and such protocols are routinely in use.

4.      Effect of Neonatal Pain on Adult behaviour   
Evidence for the long-term effect of neonatal pain on pain thresholds and behaviour in the adult is compelling but not
conclusive (Berde and Masek 1999) .  These authors suggest that "the burden of proof lies with those who would withhold analgesics" (ibid) and this is an
ethically defensible position as it would result in least harm being caused in the event of being wrong.  Neonatal rat pups exposed to repetitive acute pain have
been shown to have decreased pain thresholds and altered behaviour during adulthood (Anand et al 1999) .  The authors suggest that data from this study indicates
that repetitive pain in neonatal rat pups may lead to an altered development of the nociceptive system associated with decreased pain thresholds. Increased plasticity
of the neonatal brain may allow these and other changes in brain development to increase their vulnerability to stress disorders and anxiety-mediated adult behaviour
. Similar behavioural changes have been observed during the later childhood of pre-term neonates who were exposed to painful procedures during neonatal
intensive care (ibid).  Human male infants which have been circumcised have been shown to show increased behavioural responses to later vaccination (Taddio et al 1997)
. 
There is mounting evidence that environmental manipulations in new-born rat pups may lead to persistent changes in endocrine, immune and behavioural reactivity in
the adult (Meaney et al 1988; Pieretti et al 1991; Plotsky & Meaney 1993; Neveu et al 1994) .  Neonatally stressed rats have decreased exploratory behaviour in novel
environments, a lower threshold for learned helplessness and increased loss of hippocampal neurones associated with early onset cognitive defects in comparison with
control groups of adult rats (Meaney et al 1988; Plotsky and Meaney 1993; Landfield et al 1996) .  Even a single injection of an irritant substance into the hind paw
of a neonatal rat has been found to increase pain behaviour in the adult animal.


5.      Conclusions 
Our contemporary view of pain control mechanisms in neonatal mammals, based on scientific studies, is that descending inhibitory pathways are immature whilst
the neonate has an otherwise fully functioning nociceptive system.  Neonates show hormonal, physiological and behavioural stress responses, in response to pain,
that are similar to those produced by adults but at lower thresholds.  Neonates are therefore likely to be hypersensitive to pain, rather than hyposensitive as previously
thought.  Furthermore, there is compelling evidence that painful experiences in the neonate cause anatomical and physiological changes to the adult nervous system
which result in lower pain thresholds and increased anxiety related behaviour.  Consequently, a comprehensive and appropriate regimen of anaesthetic and analgesia,
including post operative analgesia, must be put in place to mitigate both the short and long term effects of neonatal pain arising from clinical and surgical procedures
and to address the risk of causing unnecessary suffering. 

6.    References  
Anand K J S, Coskun V, Thrivikraman K V, Nemeroff C B and Plotksy P M 1999 Long-term behavioral effects
of repetitive pain in neonatal rat pups. Physiology and Behaviour 66(4): 627-637
Berde C B and Masek B 1999 Pain in children. In: Wall P D and Melzak R (eds) Textbook of pain pp 1463-1477.
Harcourt Publishing Limited: London
Fitzgerald, M., Developmental neurobiology of pain, in Textbook of Pain, P.D. Wall and R. Melzack,
Editors. 1999, Harcourt Publishing Limited: Lodon. p. 235-251.  

Fields H L, Basbaum A I and Fields 1999 Central nervous system mechanisms of pain modulation.
In: Wall P D and Melzack R (eds) Textbook of Pain pp 309-329. Harcourt Publishing Limited: London  
Meaney M J, Sharma S, Sarrieau S and Plotsky P M 1988 Postnatal development and environmental regulation
of hippocampal glucocorticoid and mineralocorticoid receptors in the rat. Developmental Brain Research 43:158-162
Neveu P J, Deleplanque B, Puglisiallegra S, Amato F R D and Cabib S 1994 Influence of early-life events
on immune reactivity in adult mice. Developmental psychobiology 27(4): 205-213
Pieretti S, Damore A and Loizzo A 1991 Long-term changes induced by developmental handling on
pain threshold - effects of morphine and naloxone. Behaviour and Neuroscience 105(1): 215-218
Plotsky P M and Meaney M J 1993 Early postnatal experience alters hypothalamic corticotrophin
releasing factor (CRF) messenger RNA, median eminence CRF content and stress-induced release in adult rats.
Molecular Brain Research 18(3):
195-200
Taddio A, Katz J, Ilersich A L and Koren G 1997 Effect of neonatal circumcision on pain response during
subsequent routine vaccination. Lancet 349(9052): 599-603
 

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Also see Settling Doubts about Livestock Stress

Also see this important link -
Pain in Docked Cattle
Also see Sunday Times Feb. 2005 article on Pain in Neonates

Australia - Viewpoint bt Member of Christian Democratic Party
see http://www.cdp.org.au/fed/xbcomm/040404.asp

New Zealand - Council for Docked BreedsCouncil for Docked Breeds
nzscoopadapressrelease 

http://www.avar.org/taildocking.html  Tail Docking

For copyright permissions

University of Glasgow - Faculty of Veterinary Medicine - Pain & Welfare Research Group link to http://www.gla.ac.uk/vet/research/cascience/painandwelfare/projects.htm

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