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Activation and circuitry of uterine‐cervix‐related neurons in the lumbosacral dorsal root ganglia and spinal cord at parturition
Author(s) -
Puder B.A.,
Papka R.E.
Publication year - 2005
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.20690
Subject(s) - spinal cord , dorsal root ganglion , medicine , neuroscience , retrograde tracing , neuron , hypothalamus , central nervous system , biology
Abstract Stimulation of the uterine cervix at parturition activates neural circuits involving primary sensory nerves and supraspinally projecting neurons of the lumbosacral spinal cord, resulting in output of hypothalamic neurohormones. Dorsal root ganglia (DRG) and spinal neurons of these circuits are not well‐characterized. The objectives of this study were to detail the activation of DRG and spinal neurons of the L6/S1 levels that are stimulated at late pregnancy, verify hypothalamic projections of activated spinal neurons, and determine whether activated neurons express estrogen receptor‐α (ERα). Expression of phosphorylated cyclic‐AMP response element‐binding protein (PCREB) and Fos immunohistochemistry were used to “mark” activated DRG and spinal neurons, respectively. Retrograde tracing identified uterine‐cervix‐related and spinohypothalamic neurons. Baseline PCREB expression in the DRG increased during pregnancy and peaked during the last trimester. Some PCREB‐expressing neurons contained retrograde tracer identifying them as cervix‐related neurons. Fos‐expressing neurons were few in spinal cords of nonpregnant and day 22 pregnant rats but were numerous in parturient animals. Some Fos‐expressing neurons located in the dorsal half of the spinal cord contained retrograde tracer identifying them as spinohypothalamic neurons. Some DRG neurons expressing PCREB also expressed ERα, and some spinal neurons activated at parturition projected axons to the hypothalamus and expressed ERα. These results indicate that DRG and spinal cord neurons are activated at parturition; that those in the spinal cord are present in areas involved in autonomic and sensory processing; that some spinal neurons project axons to the hypothalamus, ostensibly part of a neuroendocrine reflex; and that sensory and spinal neurons can respond to estrogens. Moreover, some activated sensory neurons may be involved in the animal's perception of labor pain. © 2005 Wiley‐Liss, Inc.