AMPA-type glutamate receptor subunits 2/3 in the human trigeminal sensory ganglion and subnucleus caudalis from prenatal ages to adulthood

Using immunohistochemistry, the occurrence and distribution of the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) glutamate receptor subunits GluR2/3 is shown in the human trigeminal ganglion and subnucleus caudalis from 20 weeks of gestation to adulthood. In the trigeminal ganglion a subpopulation of GluR2/3-like immunoreactive (LI) primary sensory neurons occurred at all examined ages, amounting to about 20% of all ganglion cells in the earliest pre-term newborn and in the adult, to about 30% at 24 and 32 weeks of gestation, and peaking to about 40% in the neonate. At all ages examined, GluR2/3-LI neurons were heterogeneous in size, although in the adult most of the labeled perikarya were large-sized, with a mean cell diameter above 35 microm. In the trigeminal subnucleus caudalis, positive elements could be first detected at 30 weeks of gestation and persisted at all other examined ages. At pre- and perinatal ages, the immunoreactivity was restricted to neuronal perikarya in the superficial layers and in the marginal zone of the nucleus. In the adult tissue, the subnucleus caudalis harbored a loose meshwork of varicose thread- and dot-like elements in the superficial layers and numerous immunoreactive neurons, distributed in lamina I, substantia gelatinosa, and in the superficial zone of the magnocellular region.