The Journal of Neuroscience, January 1, 2003, 23(1):325-331
Activation of a Subset of Lumbar Spinothalamic Neurons after
Copulatory Behavior in Male But Not Female Rats
William A.
Truitt1,
Michael T.
Shipley2,
Jan G.
Veening3, and
Lique M.
Coolen1
1 Department of Cell Biology, Neurobiology, and
Anatomy, University of Cincinnati College of Medicine, Cincinnati, Ohio
45267-0521, 2 Department of Anatomy and Neurobiology,
University of Maryland, Baltimore, Baltimore, Maryland 21201, and
3 Department of Anatomy and Embryology, University of
Nijmegen, Nijmegen, 6500HB The Netherlands
The precise pathways that convey copulation-related information to
forebrain regions activated during male and female sexual behavior are
poorly understood. Previous work from our laboratory and others has
demonstrated the existence of a spinothalamic pathway that is a
candidate to relay information to these areas. This pathway originates
from a population of spinothalamic neurons in the lumbar spinal cord
containing several neuropeptides including galanin, located in laminas
7 and 10 of the lumbar segments 3 and 4. To investigate the involvement
of these lumbar spinothalamic neurons in conveying copulation-related
information, we tested the hypothesis that these cells are activated
after ejaculation in male rats and vaginocervical stimulation in female
rats. This was assessed using galanin or cholecystokinin as a marker
for this subset of spinothalamic neurons and Fos-immunoreactivity as a
marker for neuronal activation. The results demonstrated that
activation of these spinothalamic neurons is triggered by stimuli
associated with ejaculation. Fos induction was specifically associated
with ejaculation, because mounts or intromissions did not trigger
expression. Moreover, these spinothalamic neurons were not activated by
vaginocervical stimulation in female rats. Spinothalamic neurons have
generally been associated with signaling pain and temperature
information. The present findings demonstrate that a specific
subpopulation of spinothalamic neurons signals information associated
with ejaculation.
Key words:
Fos; spinal cord; thalamus; sexual behavior; galanin; spinothalamic
Copyright © 2003 Society for Neuroscience 0270-6474/03/231325-07$05.00/0