ZD 7288, an HCN channel blocker, attenuates chronic visceral pain in irritable bowel syndrome-like rats

Figure 1 Behavioral evaluation of visceral pain. A: Schematic drawings illustrating the visually based behavioral scale of the abdominal withdrawal reflex (AWR) in response to graded colorectal distension (CRD). AWR scores are 0, 1, 2, 3, and 4; B: AWR scores of control and irritable bowel syndrome (IBS)-like rats; C: Pain thresholds measured by AWR in rats. The AWR threshold indicates CRD intensity when the AWR score is 3. ^aP < 0.05 compared with control rats.

Figure 2 Electromyographic responses to colorectal distension in rats. The average responses to graded colorectal distension (CRD) were significantly increased in irritable bowel syndrome (IBS)-like rats compared with control rats. ^bP < 0.01, compared with control rats at the same CRD intensity. EOMA: External oblique muscle of the abdomen.

Figure 3 Inhibitory effects of ZD 7288 on amplitudes of external oblique muscle of the abdomen in irritable bowel syndrome-like rats. ^aP < 0.05, compared with saline-treated irritable bowel syndrome (IBS)-like rats; ^dP < 0.01, compared with IBS-like rats receiving 50 nmol/L ZD 7288. EOMA: External oblique muscle of the abdomen; CRD: colorectal distension.

Figure 4 Inhibitory effects of ZD 7288 on abdominal withdrawal reflex scores (A) and pain thresholds (B) of irritable bowel syndrome-like rats. ^aP < 0.05, compared with saline-treated IBS-like rats; ^dP < 0.01, compared with IBS-like rats receiving 50 nmol/L ZD 7288. CRD: Colorectal distension; AWR: Abdominal withdrawal reflex.

Figure 5 Effects of ZD 7288 on amplitudes of external oblique muscle of the abdomen in control rats. EOMA: External oblique muscle of the abdomen; CRD: Colorectal distension.