Anti-Docking Alliance
Campaign to end the docking of dogs' tails (and cropping of ears)
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Anti-Docking Alliance |
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Campaign to end the docking of dogs' tails (and cropping of ears) |
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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 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
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
of repetitive pain in neonatal rat pups. Physiology and Behaviour 66(4): 627-637
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.
In: Wall P D and Melzack R (eds) Textbook of Pain pp 309-329. Harcourt Publishing Limited: London
of hippocampal glucocorticoid and mineralocorticoid receptors in the rat. Developmental Brain Research 43:158-162
on immune reactivity in adult mice. Developmental psychobiology 27(4): 205-213
pain threshold - effects of morphine and naloxone. Behaviour and Neuroscience 105(1): 215-218
releasing factor (CRF) messenger RNA, median eminence CRF content and stress-induced release in adult rats.
Molecular Brain Research 18(3): 195-200
subsequent routine vaccination. Lancet 349(9052): 599-603
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Also see this important link -
Also see Sunday Times Feb. 2005 article on Pain in Neonates
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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The Campaign Against the Docking of Dogs' Tails (and cropping of ears) |
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