title: Prolactin modulates TRPV1 in female rat trigeminal sensory neurons.
abstract: Sex dependency in pain perception is well documented and is thought to be attributable to the effect of reproductive hormones on nociceptive processing. In the present study, we evaluated whether estradiol alters gene transcription in the trigeminal ganglia (TG) of ovariectomized rats (OVX). These experiments demonstrated a dramatic (40-fold) upregulation of prolactin (PRL) expression in TG by 17-beta-estradiol (E2). PRL expression was restricted to TG neurons and was highly overlapped with transient potential receptor vanilloid type 1 (TRPV1) (approximately 90%) in TG. Additionally, PRL is released from neurons during stimulation. Both forms of PRL receptors (PRLRs), short and long, were also present in TG neurons. Moreover, expression of the long PRLRs was under control of estradiol. We next evaluated the novel hypothesis that PRL acts as a neuromodulator of sensory neurons. PRL pretreatment significantly enhanced capsaicin-evoked inward currents, calcium influx, and immunoreactive calcitonin gene-related peptide release from cultured TG neurons. This PRL modulation of capsaicin responses was abolished by withdrawal of E2 from TG cultures. Biochemical analysis demonstrated that PRL increased (>50%) phosphorylation levels of TRPV1 in TG. In a behavioral test, PRL pretreatment significantly potentiated capsaicin-evoked nocifensive behavior in female rats at proestrous and in OVX rats after E2 treatment. The in vivo potentiating effect of PRL on capsaicin responses was also dependent on E2. Collectively, these data demonstrate that PRL is a novel modulator of sensory neurons tightly regulated by E2. These findings are consistent with the hypothesis that PRL could contribute to the development of certain pain disorders, possibly including those modulated by estrogen.
authors.affiliation: Department of Pharmacology, University of Texas Health Science Center at San Antonio, San Antonio, Texas 78229-3900, USA.
authors.forename: Anibal
authors.initials: A
authors.lastname: Diogenes
authors.forename: Amol M
authors.initials: AM
authors.lastname: Patwardhan
authors.forename: Nathaniel A
authors.initials: NA
authors.lastname: Jeske
authors.forename: Nikita B
authors.initials: NB
authors.lastname: Ruparel
authors.forename: Vincent
authors.initials: V
authors.lastname: Goffin
authors.forename: Armen N
authors.initials: AN
authors.lastname: Akopian
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Hargreaves
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000008:administration & dosage*; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D009419:Nerve Tissue Proteins / Q000378:metabolism*; D009475:Neurons, Afferent / Q000187:drug effects / Q000502:physiology*; D010052:Ovariectomy; D017288:Pain Threshold / Q000187:drug effects / Q000523:psychology*; D011388:Prolactin / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D050916:TRPV Cation Channels / Q000378:metabolism*; D012668:Trigeminal Ganglion / Q000187:drug effects / Q000502:physiology*
chemical_list: D009419:Nerve Tissue Proteins; D050916:TRPV Cation Channels; C493922:Trpv1 protein, rat; D004958:Estradiol; D011388:Prolactin