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

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. Pretreatment of the rats with an intracerebroventricular (i.c.v.) injection of 6-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. 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. Diphenhydramine, cimetidine, naloxone and theophylline, all administered i.c.v., did not modify the antisecretory effect of i.c.v. PGE2. The results suggest that an activation of alpha 2-adrenoceptors in the brain is involved in the central gastric antisecretory effect of PGE2, whereas neither central 5-hydroxytryptamine receptors, alpha 1- or beta-adrenoceptors, D2-dopamine receptors, histamine or opioid receptors nor adenosine seem to play any role here.