Journal of Neuroscience, Vol 6, 1537-1544, Copyright © 1986 by Society for Neuroscience
Changes in 3H-substance P receptor binding in the rat brain after kainic acid lesion of the corpus striatum
PW Mantyh and SP Hunt
Previous studies have indicated that the substantia nigra contains the
highest concentration of substance P-like immunoreactivity (SPLI) in the
brain. Paradoxically, it also appears to contain one of the lowest
concentrations of substance P receptors in the brain. One possibility is
that the massive amount of SPLI blocks the binding of the radioligand to
the substance P receptor and/or "down-regulates" the number of substance P
receptors present in this structure. Since greater than 95% of the SPLI
within the substantia nigra originates from the corpus striatum, we have
lesioned this area and measured the changes in substance P receptor
concentration in the substantia nigra and other corpus striatal projection
areas. A semiquantitative autoradiographic technique for measuring the
binding of 3H-substance P to substance P receptors was used in conjunction
with tritium-sensitive film. 3H-substance P binding was measured in both
the corpus striatum and its projection areas after kainic acid lesion of
the corpus striatum. At either 4 or 21 d after the lesion there was
approximately a 90% loss of substance P receptors in the rostral striatum,
a 74% loss in the globus pallidus, a 57% increase in receptor number in
lamina I and II of the ipsilateral somatosensory cortex, and no apparent
change in the number of receptors in the substantia nigra pars reticulata,
superior colliculus, and central gray. These findings suggest that the low
concentration of substance P receptors found within the substantia nigra is
not due the massive SPLI innervation, since removal of greater than 95% of
the SPLI had no measurable effect on the concentration of substance P
receptors.(ABSTRACT TRUNCATED AT 250 WORDS)