Neonatal Bladder Inflammation Reduces Stress‐Induced Opioidergic Inhibition of Visceromotor Responses to Urinary Bladder Distension in Adult Rats

Abstract

ObjectiveThe present study sought to determine the effect of the opioid antagonist naloxone on stress‐induced analgesia and stress‐induced hyperalgesia (SIH) mechanisms in adult rats which experienced bladder inflammation as neonates.MethodsFemale rat pups (P14–16) were anesthetized and treated with intravesical 1% zymosan (ZY− rats). Control pups were only anesthetized (AN− rats). As adults, rats were separated into acute footshock (‐FS‐; 15 min, 1 mA, 1 S duration) or non‐footshock (‐NFS‐) groups & further subdivided into naloxone‐treated (1 mg/kg; ‐NAL) and saline‐treated (−SAL) subgroups. These rats were anesthetized immediately following FS or NFS treatments, drugs given i.p.and visceromotor responses (VMR) to phasic, graded urinary bladder distension (UBD) determined.ResultsThere was no significant effect of naloxone treatment on UBD‐related SIH observed in ZY‐rats (VMRs of ZY‐FS‐NAL rats = ZY‐FS‐SAL rats > ZY‐NFS‐NAL rats = ZY‐NFS‐SAL rats). In contrast, naloxone treatment revealed a reactive opioidergic suppression of SIH in AN‐rats (VMRs of AN‐FS‐NAL rats > other AN− groups).ConclusionsThese data support the assertion that neonatal bladder inflammation results in the failure of an opioidergic inhibitory system which is activated by acute stress, the results of which is magnification of the concurrent pronociceptive processes related to visceral SIH. Supported by DK51413