PROCEEDING OF THE JOINT MEETING OF THE Italian and British Pharmacological Societies

Abstract

Some CCK-like peptides were tested for their effects on gastric emptying in the rat, taking into account their spasmogenic action on the gastroduodenal junction observed in previous papers (Bertaccini, Impicciatore & De Caro, 1973; Bertaccini, Impicciatore, De Caro, Chiavarini & Burani, 1974). Gastric emptying of a phenol red meal was evaluated by a modification (Scarpignato and Bertaccini, 1980) of the method described by Reynell & Spray (1956). Male rats weighing 200 g were used after a fasting period of 24 h. Peptides used were: caerulein, C-terminal heptapeptide of CCK (hepta-CCK) and pentagastrin. They were injected i.p. in a constant volume of 1 ml/kg 5 min prior to administration of the meal. Rats were killed at various time intervals to evaluate the duration of the effect. A fixed time (20 min) was selected for the study of the dose-response relationship. All the peptides delayed gastric emptying in a dosedependent fashion: threshold doses were 0.075 .g/kg for caerulein and hepta-CCK. Both peptides caused a complete block of gastric emptying with doses of 5 gg/kg. Pentagastrin had a threshold dose at 10 pg/kg; the maximum dose (80 pg/kg) caused an 104P PROCEEDINGS OF THE B.P.S., 30th JUNE, 1st JULY, 1980 Table I 'Characteristics' of emptying patterns Calculated Half-life emptying time Treatment (min) (min) Controls 15.3 + 6.2' 120.9 + 6.1 Caerulein (1 bg/kg) 49.0 + 14.32 220.6 + 14.32 Hepta-CCK (1 p.g/kg) 53.3 + 14.32 289.3 + 14.22 Pentagastrin (80 bg/kg) 23.8 + 7.73 146.0 + 7.73 1 Mean value + 95W confidence limits. 2 Statistically significant difference (P < 0.001) in comparison with control values. Statistically significant difference (P < 0.01) in comparison with control values. suggest that the delay in gastric emptying induced by CCK-like peptides is connected with the contraction of the pylorus pointed out in previous studies. Therefore the pyloric sphincter appears to play an important role in the regulation of emptying of liquids in rats, unlike cats and dogs (Stemper & Cooke, 1976) in which gastric emptying of liquids was shown to be independent of the gastroduodenal junction.