Neurokinin-1 receptor blocker CP-99 994 improved emesis induced by cisplatin via regulating the activity of gastric distention responsive neurons in the dorsal motor nucleus of vagus and enhancing gastric motility in rats

Background: Nowadays, chemotherapy induced nausea and vomiting (CINV) is still common in patients with cancer. It was reported that substance P mediated CINV via neurokinin-1 (NK1) receptor and antagonists of NK1 receptor has been proved useful for treating CINV but the mechanism are not fully understood. This study aimed to examine the role of NK1 receptor blocker, CP-99 994, when administrated into dorsal motor nucleus of vagus (DMNV), on the cisplatin-induced emesis in rats and the possible mechanism. Methods: Rats' kaolin intake, food intake, and bodyweight were recorded every day; gastric contraction activity was recorded in conscious rats through a force transducer implanted into the stomach; gastric emptying was monitored using the phenol red method; single unit extracellular firing in the DMNV were recorded. Key Results: DMNV microinjection of CP-99 994 reduced the changes of increased kaolin consumption and suppressed food intake in cisplatin-treated rats; enhanced the gastric contraction activity dose-dependently in control and cisplatin-treated rats but enhanced gastric emptying only in cisplatin-treated rats; reduced the firing rate of gastric distention inhibited (GD-I) neurons but increased the firing rate of GD excited (GD-E) neurons in the DMNV. The effects of CP-99 994 on gastric motility and neuronal activity were stronger in cisplatin-treated rats than those of control rats. Conclusions and Inferences: Our results suggested that CP-99 994 could improve emesis induced by cisplatin by regulating gastric motility and gastric related neuronal activity in the DMNV.