Long term estradiol-17β administration changes population of the dorsal root ganglia neurons innervating the ovary in the sexually mature gilts

Abstract

The influence of estradiol-17β (E₂) overdose on the number and distribution of neurons in the dorsal root ganglia (DRGs) supplying the ovary of adult pigs was investigated. The numbers of ovarian substance P (SP)-, calcitonin gene-related peptide (CGRP)-, galanin (GAL)-, pituitary adenylate cyclase-activating polypeptide (PACAP)-, neuronal isoform of nitric oxide synthase (nNOS)- and estrogen receptors (ERs)-immunoreactive perikarya were also determined. On day 3 of the estrous cycle, the ovaries of both the control and experimental gilts were injected with retrograde tracer Fast Blue. From day 4 of the estrous cycle to the expected day 20 of the second studied cycle, the experimental gilts were injected with E₂, while the control gilts received oil. The DRGs Th16-L5 were then collected and processed for double-labelling immunofluorescence. Injections of E₂ increased the E₂ level in the peripheral blood ∼4-5-fold and reduced the following in the DRGs: the total number of Fast Blue-positive perikarya, the number of large perikarya, the population of perikarya in the L2 and L3 ganglia, the numbers of SP- and/or CGRP-, PACAP-, nNOS-immunoreactive perikarya and the number of large perikarya expressing ERs subtype α and β. These results show that long-term E₂ treatment of adult gilts affects both the spatial and neurochemical organization pattern of ovary sensory innervation. Our findings suggest that elevated E₂ levels occurring during pathological states may regulate the transmission of sensory modalities from the ovary to the spinal cord.