3 -  Neuropeptides
Kungel and Friauf (1995) discovered an early
transient expression of the neuropeptide somatostatin
in auditory nuclei of embryonic rats, followed by
postnatal proliferation of leu-enkephalin neurons [1].  
They proposed that the early appearance of these
peptides in the auditory pathway may have special
importance in promoting synaptic connections, and
that transmitters like somatostatin primarily serve a
developmental role.  Uhl et al. (1979) mapped
enkephalin peptides in mature rats, and made special
note of rich innervation in the auditory system,
including the inferior colliculus [2].  Relative density of
enkephalin receptors in the inferior colliculus and
neighboring brainstem sites can be seen in the
autoradiograph pictures in the article by Delfs et al.
(1994) [3].

Enkephalins are thought to mediate pleasure.  That
they are prominent in the auditory system suggests
they may be part of the mechanism that propagates
the energizing, motivational, and emotion evoking
effects of music.  Auditory excitation of the brain's
memory system may be important throughout life.  
The discovery of enkephalin peptides came long after
much research had been done on the effects of
opiates, and in response to the question of why opiate
receptors should be present in the brain (Snyder
1986).  Now the effects of more and more drugs are
being studied with the deoxyglucose method of
Sokoloff (1981), and use of drugs as probes to
investigate enzyme systems within neurons that
regulate neurotransmission may have relevance for
research in autism.

1. Kungel M and Friauf E (1995). Somatostatin and leu-enkephalin in the rat auditory brainstem
   during fetal and postnatal development.  Anatomy and Embryology, 191, 425-443.
   
2. Uhl GR, Goodman RR, Kuhar M.J, Childers SR, Snyder SH (1979) Immunohistochemical
   mapping of enkephalin containing cell bodies, fibers and nerve terminals in the brain stem of
   the rat. Brain Research 166:75-94.
   
3. Delfs JM, Kong H, Mester A, Chen Y, Yu L, Reisine T, Chesselet M-F (1994) Expression of mu
   opiod receptor mRNA in rat brain: an in situ hybridization study at the single cell level.  Journal
   of Comparative Neurology 345:46-68.
   
4. Snyder S (1986) Drugs and the Brain.  New York: Scientific American Library.
   
5. Sokoloff L (1981) Localization of functional activity in the central nervous system by
   measurement of glucose utilization with radioactive deoxyglucose.  Journal of Cerebral Blood
   Flow and Metabolism 1:7-36.
   

References

Full References

1. Kungel M, Friauf E (1995).
   Somatostatin and leu-
   enkephalin in the rat auditory
   brainstem during fetal and
   postnatal development.
   
2. Uhl GR et al. (1979)
   Immunohistochemical
   mapping of enkephalin
   containing cell bodies, fibers
   and nerve terminals in the
   brain stem of the rat.
   
3. Delfs JM et al. (1994)
   Expression of mu opiod
   receptor mRNA in rat brain: an
   in situ hybridization study at
   the single cell level.
   
4. Snyder S (1986) Drugs and
   the Brain.
   
5. Sokoloff L (1981) Localization
   of functional activity in the
   central nervous system by
   measurement of glucose
   utilization with radioactive
   deoxyglucose.
   

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