Effect of dexloxiglumide and spiroglumide, two new CCK-receptor antagonists, on gastric emptying and secretion in the rat: evaluation of their receptor selectivity in vivo

Background: Clear definition of the role of CCK in the physiology of gastric motor activity has been long hampered by the lack of specific and potent nonpeptide antagonists of CCK-receptors. The availability of such compounds has stimulated a broad array of investigations into the physiological actions of this hormone and to examine its putative role in certain diseases.

Aims: The effect of two recently developed CCK-receptor antagonists, namely dexloxiglumide and spiroglumide, on gastric emptying and secretion as well as their selectivity towards CCKA- and CCKB-receptors in vivo was studied in the rat.

Methods: Gastric emptying was quantified by using a liquid noncaloric meal labelled with phenol red. Acid secretion was measured by titration in conscious rats.

Results: The putative CCKA-antagonist, dexloxiglumide, administered by intravenous route, was able to inhibit CCK-8-induced delay of gastric emptying in a dose-dependent fashion, with an ID50 (95% CL) of 1.14 (0.84-1.53) mg/kg. Similarly, the putative CCKB-gastrin-antagonist, spiroglumide, proved to be capable of inhibiting dose-dependently pentagastrin-induced acid hypersecretion, its ID50 being 20.1 (8.67-46.4) mg/kg. On the other hand, dexloxiglumide, at doses able to almost completely block CCKA mediated effects (i.e. delay of gastric emptying), was ineffective against pentagastrin-induced acid hypersecretion. Similarly, spiroglumide, at doses which inhibit by 55% CCKB-gastrin mediated effects (i.e. acid secretion) was inactive when tested against CCK-8 induced delay of gastric emptying.

Conclusions: These results demonstrate in vivo that dexloxiglumide is a selective antagonist for CCKA-receptors whereas spiroglumide is selective for CCKB-gastrin-receptors. These compounds are therefore useful tools for discriminating between different subclasses of CCK-receptors in vivo and might have a therapeutic potential in motility or acid-related disorders.