The Journal of Neuroscience, April 1, 1999, 19(7):2823-2833
Central Neuronal Circuit Innervating the Lordosis-Producing
Muscles Defined by Transneuronal Transport of Pseudorabies Virus
Derek
Daniels1,
Richard
R.
Miselis2, 3, and
Loretta M.
Flanagan-Cato1, 3
Departments of 1 Psychology and 2 Animal
Biology and 3 Institute for Neurological Sciences,
University of Pennsylvania, Philadelphia, Pennsylvania 19104-6196
The lordosis reflex is a hormone-dependent behavior displayed by
female rats during mating. This study used the transneuronal tracer
pseudorabies virus (PRV) to investigate the CNS network that controls
the lumbar epaxial muscles that produce this posture. After PRV was
injected into lumbar epaxial muscles, the time course analysis of CNS
viral infection showed progressively more PRV-labeled neurons in higher
brain structures after longer survival times. In particular, the
medullary reticular formation, periaqueductal gray (PAG), and
ventromedial nucleus of the hypothalamus (VMN) were sequentially
labeled with PRV, which supports the proposed hierarchical network of
lordosis control. Closer inspection of the PRV-immunoreactive neurons
in the PAG revealed a marked preponderance of spheroid neurons, rather
than fusiform or triangular morphologies. Furthermore,
PRV-immunoreactive neurons were concentrated in the ventrolateral
column, rather than the dorsal, dorsolateral, or lateral columns of the
PAG. Localization of the PRV-labeled neurons in the VMN indicated that
the majority were located in the ventrolateral subdivision, although
some were also in other subdivisions of the VMN. As expected, labeled
cells also were found in areas traditionally associated with
sympathetic outflow to blood vessels and motor pathways, including the
intermediolateral nucleus of the spinal cord, the paraventricular
hypothalamic nucleus, the red nucleus, and the motor cortex. These
results suggest that the various brain regions along the neuraxis
previously implicated in the lordosis reflex are indeed serially connected.
Key words:
epaxial muscles; lordosis; motor control; periaqueductal
gray; pseudorabies virus; sexual behavior; ventromedial
hypothalamus
Copyright © 1999 Society for Neuroscience 0270-6474/99/1972823-11$05.00/0