Dignify Therapeutics LLC, Research Triangle Park, NC, USA.
J Basic Clin Physiol Pharmacol. 2022 Nov 16;34(2):227-233. doi: 10.1515/jbcpp-2022-0119. eCollection 2023 Mar 1.
Neurokinin 2 receptor (NK2R) agonists may be useful for treating bladder and bowel dysfunction via direct contraction of detrusor and gastrointestinal smooth muscle. The NK2R agonist [Lys5, MeLeu9, Nle10]-NKA(4-10) (LMN-NKA) induces urination and defecation, but also produces the potential side effect of dermal flushing in rats. Although LMN-NKA is a NK2R agonist, it also has affinity for neurokinin 1 receptors (NK1R). Therefore, the goal of this study was to determine the neurokinin receptor (NKR) subtypes responsible for LMN-NKA-induced urination, defecation, and flushing by blocking either NK2Rs or NK1Rs before LMN-NKA administration.
To accomplish this goal, we developed a simple high-throughput 'rapid detection voiding assay' to detect rapid-onset drug-induced urination and defecation in rats. In LMN-NKA dose-response experiments, LMN-NKA (10-100 μg/kg, subcutaneous) was injected and urination, defecation, and flushing were monitored for 30 min. For NKR antagonist experiments, vehicle, the NK2R antagonist GR159897, or the NK1R antagonist CP-99,994 were injected before an acclimation period. Following acclimation, saline or 100 μg/kg LMN-NKA were injected, and behavior was observed for 30 min.
LMN-NKA produced dose-related increases in urination, defecation, and flushing. Blocking NK2Rs reduced urination and blocked defecation, without affecting flushing. Blocking NK1Rs did not change LMN-NKA-induced urination or defecation but reduced LMN-NKA-induced flushing.
Using the rapid detection voiding assay we show that LMN-NKA-induced urination and defecation are mediated by NK2Rs, while flushing is mediated by NK1Rs. Therefore, drugs that are more selective for NK2 vs. NK1Rs should produce rapid-onset urination and defecation without producing the potential side effect of flushing.
神经激肽 2 受体（NK2R）激动剂可通过直接收缩逼尿肌和胃肠道平滑肌，用于治疗膀胱和肠道功能障碍。NK2R 激动剂[Lys5，MeLeu9，Nle10]-NKA（4-10）（LMN-NKA）可引起排尿和排便，但也会导致大鼠出现潜在的皮肤潮红副作用。尽管 LMN-NKA 是一种 NK2R 激动剂，但它也对神经激肽 1 受体（NK1R）具有亲和力。因此，本研究的目的是通过在给予 LMN-NKA 之前阻断 NK2R 或 NK1R，确定负责 LMN-NKA 诱导的排尿、排便和潮红的神经激肽受体（NKR）亚型。
为了实现这一目标，我们开发了一种简单的高通量“快速检测排尿测定法”，以检测大鼠中快速发作的药物诱导的排尿和排便。在 LMN-NKA 剂量反应实验中，皮下注射 LMN-NKA（10-100μg/kg），并监测 30 分钟的排尿、排便和潮红。对于 NKR 拮抗剂实验，在适应期之前注射载体、NK2R 拮抗剂 GR159897 或 NK1R 拮抗剂 CP-99994。适应后，注射生理盐水或 100μg/kg LMN-NKA，并观察 30 分钟的行为。
LMN-NKA 产生了与剂量相关的排尿、排便和潮红增加。阻断 NK2R 减少了排尿并阻断了排便，而不影响潮红。阻断 NK1R 没有改变 LMN-NKA 诱导的排尿或排便，但减少了 LMN-NKA 诱导的潮红。
使用快速检测排尿测定法，我们表明 LMN-NKA 诱导的排尿和排便由 NK2R 介导，而潮红由 NK1R 介导。因此，对 NK2 与 NK1R 更具选择性的药物应产生快速发作的排尿和排便，而不会产生潜在的潮红副作用。
