Volume 17, Number 19,
Issue of October 1, 1997
pp. 7372-7384
Copyright ©1997 Society for Neuroscience
Deafferentation Causes Apoptosis in Cortical Sensory Neurons in
the Adult Rat
Received April 18, 1997; revised June 9, 1997; accepted July 10, 1997.
Sabrina A. Capurso1, 4,
Michael E. Calhoun4,
Renat
R. Sukhov4,
Peter R. Mouton1, 4,
Donald L. Price1, 2, 3, 4, and
Vassilis E. Koliatsos1, 2, 3, 4
Departments of 1 Pathology, 2 Neurology,
and 3 Neuroscience and 4 Division of
Neuropathology, The Johns Hopkins University School of Medicine,
Baltimore, Maryland 21205-2196
The present study provides an experimental model of the apoptotic
death of pyramidal neurons in rat olfactory cortex after total
bulbectomy. Terminal transferase (TdT)-mediated deoxyuridine triphosphate (d-UTP)-biotin nick end labeling (TUNEL), DNA
electrophoresis, and neuronal ultrastructure were used to provide
evidence of apoptosis; neurons in olfactory cortex were counted by
stereology. Maximal TUNEL staining occurred in the piriform cortex
between 18 and 26 hr postbulbectomy. Within the survival times used in
the present study (up to 48 hr postlesion), cell death was observed
exclusively in the piriform cortex; there was no evidence of cell death
in any other areas connected with the olfactory bulb. Neurons
undergoing apoptosis were pyramidal cells receiving inputs from, but
not projecting to, the olfactory bulb. The apical dendrites of these neurons were contacted by large numbers of degenerating axonal terminals. Gel electrophoresis of DNA purified from lesioned olfactory cortex showed a ladder pattern of fragmentation. Inflammatory cells or
phagocytes were absent in the environment of degenerating neurons in
the early stages of the apoptotic process. The present model suggests
that deafferentation injury in sensory systems can cause apoptosis. In
addition, olfactory bulbectomy can be used for investigating molecular
mechanisms that underlie apoptosis in mature mammalian cortical neurons
and for evaluating strategies to prevent the degeneration of cortical
neurons.
Key words:
anterograde degeneration;
cell death;
DNA fragmentation;
neurodegenerative disease;
olfactory;
TUNEL