Neurokinin 2 receptor-mediated bladder and colorectal responses in aged spinal cord injured rats

STUDY DESIGN

Animal proof of principle study.

OBJECTIVES

Bladder and bowel dysfunction are common after spinal cord injury (SCI) and in the elderly. Neurokinin 2 receptor agonists are known to produce on-demand urination and defecation in adult SCI rats. This study compared the ability of a neurokinin 2 receptor (NK2R) agonist to produce bladder and colorectal contractions in both young adult and aged SCI rats.

SETTING

Dignify Therapeutics and Integrated Laboratory Systems, Durham, NC USA.

METHODS

Bladder and colorectal pressure and voiding efficiency were measured in response to the NK2R agonist, [Lys5,Me,Leu9,Nle10]-NKA_(4-10) (LMN-NKA), in anesthetized animals. The potency and efficacy of LMN-NKA was examined in young adult and aged SCI (T3 or T9 transected) rats, with young adult and aged spinal intact rats included as controls.

RESULTS

LMN-NKA (3-300 μg/kg i.v.) produced dose-dependent increases in bladder and colorectal pressure in all anesthetized rats. No differences in the bladder or colorectal pressure responses or voiding efficiency were observed with age or after SCI. The level of SCI did not change the pharmacodynamic responses to the agonist.

CONCLUSIONS

An NK2R agonist produced similar responses in young adult and aged SCI rats, suggesting this class of agonists could be used as a potential therapy to induce on-demand urination and defecation in aged populations, with or without SCI.

Tachykinin NK2 antagonist for treatments of various disease states

Tachykinin NK₂ receptors are distributed in periphery, in the smooth muscle of the respiratory, gastrointestinal, genitourinary tract, and within the brain. Substance P (SP), neurokinin A (NKA), and neurokinin B (NKB) are endogenous ligands for NK₂ receptors and are active in the peripheral and central nervous systems. NK₂ antagonists have the potential to reduce airway motor responses and prevent hyperactivity by inhibiting NKA-induced bronchoconstriction in asthmatic patients. Due to its abundance, peripherally and centrally, tachykinin NK₂ receptor antagonists have high potential in treating various disease states ranging from asthma to irritable bowel syndrome, to detrusor hyperactivity, to anxiety. This review is an evaluation of NK₂ receptor antagonists as possible therapeutics for a myriad of pharmacological treatments.