Role of putative neurotransmitters in the central gastric antisecretory effect of prostaglandin E₂ in rats

Abstract

1 The role of putative neurotransmitters of the central nervous system in the central gastric antisecretory effect of prostaglandin E2 (PGE2) was investigated in pylorus-ligated rats. 2 Pretreatment of the rats with an intracerebroventricular (i.c.v.) injection of6-hydroxydopamine (6-OHDA) prevented the antisecretory effect of the i.c.v. administration of PGE2, whereas pretreatment with 5,6-dihydroxytryptamine (5,6-DHT) plus p-chlorophenylalanine (PCPA) had no effect.3 I.c.v.-administered phentolamine and idazoxan antagonized the inhibition of gastric secretion induced by i.c.v. PGE2, whereas prazosin, propranolol and sulpiride injected via the same route were ineffective. 4 Diphenhydramine, cimetidine, naloxone and theophylline, all administered i.c.v., did not modify the antisecretory effect of i.c.v. PGE2. 5 The results suggest that an activation of a2-adrenoceptors in the brain is involved in the central gastric antisecretory effect of PGE2, whereas neither central 5-hydroxytryptamine receptors, ,-or Padrenoceptors, D2-dopamine receptors, histamine or opioid receptors nor adenosine seem to play any role here.

Effect of gastric secretagogues on the formation of inositol phosphates in isolated gastric cells of the rat

“…On the other hand, prostaglandins of A, E and I types are potent inhibitors of gastric acid secretion in various species. Studies with isolated gastric cells have demonstrated that this effect is, at least in part, due to a direct action on the parietal cells (Soll, 1981), although a central component of action seems also be of importance in the antisecretory effect of prostaglandins (Puurunen, 1983;1985). In vitro, the inhibitory action of prostaglandin E2 shows a clear selectivity in inhibiting hydrogen ion secretion induced by histamine, without having any effect on those induced by gastrin or carbachol (Soll, 1981).…”