Stimulation by nizatidine, a histamine H2-receptor antagonist, of duodenal HCO3- secretion in rats: relation to anti-cholinesterase activity

Table 1 Effects of nizatidine, neostigmine and famotidine on duodenal damage induced by acid in rats

Group	Dose (mg/kg)	Number of Rats	Duodenal damage (mm2)	Inhibition (%)
Control		5	49.1 ± 7.4
Nizatidine	10	5	21.3 ± 5.1a	56.6
Neostigmine	0.03	5	17.7 ± 7.3a	64.0
Famotidine	10	4	40.8 ± 4.5	16.1

Duodenal damage was induced by perfusing a duodenal loop with 100 mM HCl for 4 h in the presence of indomethacin (5 mg/kg, s.c.). Nizatidine (10 mg/kg), neostigmine (0.03 mg/kg) or famotidine (10 mg/kg) was administered i.v. as a single injection 20 min before the onset of acid perfusion. Data are presented as the means ± SE from 5 rats.

^a Significant difference from control, P < 0.05.

Table 2 Inhibition by nizatidine, famotidine, neostigmine and cisapride of acetylcholinesterase activity in rat erythrocyte and plasma

Drugs	IC50 (M)
	Rat erythrocytes	Plasma
Nizatidine	1.4 × 10-6	5.7 × 10-4
Neostigmine	1.1 × 10-7	3.3 × 10-6
Famotidine	1.0 × 10-3 <	1.0 × 10-3 <
Cisapride	1.0 × 10-3 <	1.0 × 10-3 <

Values represent the IC₅₀ of AChE activity for each drug. The experiments were performed in triplicate against AChE of rat erythrocyte and plasma.