Effects of oxytocin and prolactin on stress-induced bladder hypersensitivity in female rats.
Anecdotal evidence suggests that chronic bladder pain improves while breastfeeding. The present study sought to identify potential mechanisms for such a phenomenon by investigating the effects of the lactogenic hormones prolactin (PL) and oxytocin (OXY) in a rat model of bladder nociception. Lactating rats were less sensitive to urinary bladder distension (UBD) than controls. In investigating potential antinociceptive and anxiolytic roles for these hormones, we found exposure to a footshock paradigm (STRESS groups) produced bladder hypersensitivity in saline-treated rats, manifested as significantly higher electromyographical (EMG) responses to UBD, compared to rats exposed to a nonfootshock paradigm (SHAM groups). This hypersensitivity was attenuated by the intraperitoneal administration of OXY prior to footshock in the STRESS-OXY group. The administration of PL augmented EMG responses in the SHAM-PL group but had no effect on the responses of the STRESS-PL group. In the absence of behavioral pretreatment, OXY attenuated UBD-evoked responses while PL had no effect. Moreover, OXY-treated rats spent more time in the open arm of an elevated plus maze compared to saline-treated rats suggesting anxiolysis. These studies suggest the potential for systemic OXY, but not PL, as an analgesic and anxiolytic treatment for painful bladder disorders such as interstitial cystitis.


CONCLUSIONS
This study presents evidence that systemic oxytocin has both analgesic and anxiolytic properties which may make it a potentially useful agent for patients with stress-exacerbated chronic-pain syndromes such as interstitial cystitis. These studies do not suggest a similar role for prolactin.
Black
L Vandy
LV
Department of Pediatrics, Division of Pediatric Hematology and Oncology, University of Alabama at Birmingham, Birmingham, Alabama 35233, USA. vblack@peds.uab.edu
Ness
Timothy J
TJ
Robbins
Meredith T
MT
D000700:Analgesics / Q000494:pharmacology / Q000627:therapeutic use; D000818:Animals; D014151:Anti-Anxiety Agents / Q000494:pharmacology / Q000627:therapeutic use; D001007:Anxiety / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D004195:Disease Models, Animal; D004558:Electric Stimulation / Q000009:adverse effects; D005260:Female; D007274:Injections, Intraperitoneal; D007774:Lactation / Q000378:metabolism*; D018782:Maze Learning / Q000187:drug effects / Q000502:physiology; D009483:Neuropsychological Tests; D009619:Nociceptors / Q000187:drug effects / Q000502:physiology; D010121:Oxytocin / Q000378:metabolism / Q000494:pharmacology*; D010148:Intractable Pain / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D011388:Prolactin / Q000378:metabolism / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012737:Sex Factors; D013315:Stress, Psychological / Q000150:complications; D016896:Treatment Outcome; D001743:Urinary Bladder / Q000187:drug effects / Q000294:innervation / Q000503:physiopathology; D053201:Urinary Bladder, Overactive / Q000188:drug therapy* / Q000209:etiology / Q000503:physiopathology; D017833:Visceral Afferents / Q000187:drug effects / Q000503:physiopathology
D000700:Analgesics; D014151:Anti-Anxiety Agents; D010121:Oxytocin; D011388:Prolactin