Ketamine and xylazine effects in murine model of acute pancreatitis

Abstract

Ketamine and xylazine (Ket/Xyl) are anesthetic agents that target neural pathways and are commonly used in combination in mouse studies. Since neural pathways can modulate acute pancreatitis severity, we asked if Ket/Xyl affect disease severity. C57BL/6 mice were treated with six hourly injections of cerulein to induce mild acute pancreatitis. Mice were also treated with and without ketamine, xylazine, and Ket/Xyl before pancreatitis induction in vivo and in vitro. Ket/Xyl pretreatment in vivo increased selected parameters of pancreatitis severity such as trypsin activity and edema; these effects were predominantly mediated by xylazine. Ket/Xyl also changed markers of autophagy. These in vivo effects of Ket/Xyl were not attenuated by atropine. The drugs had no little to no effect on pancreatitis responses in isolated pancreatic cells or lobules. These findings suggest that Ket/Xyl administration can have substantial effect on acute pancreatitis outcomes through nonmuscarinic neural pathways. Given widespread use of this anesthetic combination in experimental animal models, future studies of inflammation and injury using Ket/Xyl should be interpreted with caution.NEW & NOTEWORTHY Ketamine and xylazine anesthetic agent administration before acute pancreatitis induction in mice lead to changes in pancreatitis responses independent of acute pancreatitis induction. Future studies should consider the potential effects of anesthesia administration when studying disease processes associated with inflammation and injury.

Keywords: anesthesia; cerulein; ketamine; pancreatitis; xylazine.

Graphical abstract

Figure 1.

Ketamine/xylazine administration before inducing cerulein pancreatitis affects functional assays in male and female mice. In serum amylase at baseline and fold change over control (A), pancreatic trypsin activity at baseline and fold change over control (B), pancreatic chymotrypsin activity at baseline and fold change over control (C), and pancreatic edema by wet/dry weight at baseline and fold change over control (D). Means ± SD. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001, ****P ≤ 0.0001. Female mice denoted in blue. Cer, cerulein; Ket/Xyl, ketamine/xylazine.

Figure 2.

Ketamine/xylazine administration before inducing cerulein pancreatitis changes histological disease features in male and female mice. Clear vacuole formation (arrow) at baseline and fold change over control (A), filled vacuole formation (arrow) at baseline and fold change over control (B), and necrosis at baseline and fold change over control (C). Representative histology of female mice at ×40 are shown in D. Means ± SD. *P ≤ 0.05, **P ≤ 0.01, ***P ≤ 0.001. Female mice denoted in blue. Cer, cerulein; Ket/Xyl, ketamine/xylazine.

Figure 3.

Ketamine/xylazine reduces apoptosis and neutrophil infiltration but increases a proliferative marker during pancreatitis. Pancreatic TUNEL levels (A) and staining in mice with and without ketamine/xylazine pretreatment (B). Representative immunohistochemistry for TUNEL staining at ×40 are shown in B. C: Ly6b staining scores for neutrophil infiltration. D: Ki67 staining scores for proliferation. Means ± SD. *P ≤ 0.05, **P ≤ 0.01. Cer, cerulein; Ket/Xyl, ketamine/xylazine. ≥2 male and female mice per testing condition.

Figure 4.

Ketamine and xylazine have distinct effects on cerulein-induced acute pancreatitis: (A) serum amylase secretion, (B) pancreatic trypsin activity, (C) pancreatic chymotrypsin activity, and (D) pancreatic edema by dry/wet weight. Means ± SD. *P ≤ 0.05, **P ≤ 0.01, ****P ≤ 0.0001. Cer, cerulein; Ket/Xyl, ketamine/xylazine; Xyl, xylazine; Ket, ketamine. ≥2 male and female mice per testing condition.

Figure 5.

Ketamine and xylazine affect pancreatitis histology differently: clear vacuoles (A), filled vacuoles (B), and necrosis (C). Means ± SD. *P ≤ 0.05, **P ≤ 0.01. Cer, cerulein; Ket/Xyl, ketamine/xylazine; Xyl, xylazine; Ket, ketamine. ≥2 male and female mice per testing condition.

Figure 6.

Ketamine and xylazine affect autophagy markers differently. Integrated density of p62 (A) and LC3-2 (B) on Western blots. Fold over control integrated density from p62 (C) and LC3-2 (D) Western blots with and without pretreatment, xylazine pretreatment, or ketamine pretreatment. E: representative Western blot. Means ± SD. *P ≤ 0.05). Cer, cerulein; Ket/Xyl, ketamine/xylazine; Xyl, xylazine; Ket, ketamine.

Figure 7.

Ketamine/xylazine treatment before cerulein treatment does not increase pancreatitis responses in acini: trypsin activity (A), chymotrypsin activity (B), and amylase secretion (C). Acini were collected from ≥2 male and female mice per testing condition. Means ± SD. Cer, cerulein; Ket/Xyl, ketamine/xylazine.