Neuronal aromatase expression in pain processing regions of the medullary and spinal cord dorsal horn. Issue 16 (24th July 2017)

• Record Type: Journal Article
• Authors: Tran, May; Kuhn, Julia A.; Bráz, João M.; Basbaum, Allan I.
• Is Part Of: Journal of comparative neurology. Volume 525:Issue 16(2017)
• Page Start: 3414
• Page End: 3428
• Publication Date: 2017-07-24
• Subjects: aromatase -- estrogens -- pain -- solitary nucleus -- spinal cord dorsal horn -- trigeminal caudal nucleus -- RRID:MGI:4430066 -- RRID:MGI:5634564; Comparative neurobiology -- Periodicals; Neurology -- Periodicals; 616
• DOI: 10.1002/cne.24269
• Languages: English
• ISSNs: 0021-9967

Abstract

Abstract: In both acute and chronic pain conditions, women tend to be more sensitive than men. This sex difference may be regulated by estrogens, such as estradiol, that are synthesized in the spinal cord and brainstem and act locally to influence pain processing. To identify a potential cellular source of local estrogen, here we examined the expression of aromatase, the enzyme that catalyzes the conversion of testosterone to estradiol. Our studies focused on primary afferent neurons and on their central targets in the spinal cord and medulla as well as in the nucleus of the solitary tract, the target of nodose ganglion‐derived visceral afferents. Immunohistochemical staining in an aromatase reporter mouse revealed that many neurons in laminae I and V of the spinal cord dorsal horn and caudal spinal trigeminal nucleus and in the nucleus of the solitary tract express aromatase. The great majority of these cells also express inhibitory interneuron markers. We did not find sex differences in aromatase expression and neither the pattern nor the number of neurons changed in a sciatic nerve transection model of neuropathic pain or in the Complete Freund's adjuvant model of inflammatory pain. A few aromatase neurons express Fos after cheek injection of capsaicin, formalin, or chloroquine. In total, given their location, these aromatase neurons are poised to engage nociceptive circuits, whether it is through local estrogen synthesis or inhibitory neurotransmitter release. Abstract : Using an aromatase reporter mouse, we identified Pax‐2 positive, inhibitory interneurons in laminae I and V of the spinal and medullary dorsal horns. These neurons likely synthesize estrogen and are ideally positioned to influence pain‐processing circuits.