Glutamate and metabotropic glutamate receptors associated with innervation of the uterine cervix during pregnancy: receptor antagonism inhibits c-Fos expression in rat lumbosacral spinal cord at parturition.
Dorsal root ganglia (DRG) neurons connect the spinal cord and uterine cervix, and are activated at parturition with subsequent stimulation of secondary neurons in the spinal dorsal horn and autonomic areas. Neuropeptide neurotransmitters and receptors have been studied in these areas, but amino acid transmitters, e.g., glutamate, an excitatory neurotransmitter involved in sensory and nociceptive processing, have not been characterized. To determine if glutamate is involved in innervation of the cervix, rats were examined for markers of glutamatergic neurons in the L6-S1 spinal cord, DRG and cervix. Metabotropic glutamate receptors mGluR5 in the spinal dorsal horn and their expression over pregnancy were examined in pregnant rats and pregnant rats treated continuously with an antagonist of mGluR5, 2-methyl-6-(phenylethynyl) pyridine (MPEP). Rats were allowed to deliver pups to determine if the antagonist altered the expression of an early response gene protein, Fos, in the L6-S1 cord. Immunohistochemistry showed glutamate- and vesicular glutamate transporter1 (VGluT1)-positive fibers in the cervix, glutamate- and VGluT1-expressing neurons in the DRG, some of which also exhibited retrograde tracer from cervical injections, and VGluT1 and mGluR5 immunoreactivities in the L6-S1 spinal dorsal horns. Expression of mGluR5 receptors increased over pregnancy. Fos-positive neurons were present among mGluR5-immunoreactivity in the spinal dorsal horn. Parturition-induced Fos-positive neurons in the spinal cords were abundant in control rats, but were reduced by 70% in MPEP-treated animals. These results suggest that glutamate is likely involved in the transmission of sensory signals, possibly pain, from the cervix to the spinal cord at parturition.
Ghosh
Chaitali
C
Northeastern Ohio Universities College of Medicine, Department of Neurobiology, Rootstown, OH 44272, USA.
Storey-Workley
Megan
M
Usip
Sharon
S
Hafemeister
Jen
J
Miller
Kenneth E
KE
Papka
Raymond E
RE
D000818:Animals; D002584:Cervix Uteri / Q000294:innervation*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005260:Female; D005727:Ganglia, Spinal / Q000166:cytology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D005971:Glutamates / Q000378:metabolism*; D008161:Lumbosacral Region; D009474:Neurons / Q000187:drug effects; D016761:Oncogene Proteins v-fos / Q000378:metabolism; D036801:Parturition / Q000378:metabolism*; D011247:Pregnancy / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D013116:Spinal Cord / Q000187:drug effects / Q000502:physiology*; D050598:Vesicular Glutamate Transport Protein 1 / Q000378:metabolism
D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; C578937:Grm5 protein, rat; D016761:Oncogene Proteins v-fos; D011725:Pyridines; D012333:RNA, Messenger; D064529:Receptor, Metabotropic Glutamate 5; D018094:Receptors, Metabotropic Glutamate; D050598:Vesicular Glutamate Transport Protein 1; C121465:6-methyl-2-(phenylethynyl)pyridine