A Modulating Role of Prostaglandins in Contractions of the Guinea‐pig Ileum

Abstract

1The role of prostaglandins in contractions of the guinea-pig ileum evoked either directly by acetylcholine or indirectly by angiotensin and by coaxial stimulation has been investigated. 2 Prostaglandin E2 in low concentration (6 nM) slightly augmented both types of contraction. Indomethacin, an inhibitor of prostaglandin synthesis, markedly reduced the indirectly evoked contractions but did not affect contractions in response to acetylcholine. The addition of prostaglandin E2 to the preparation treated previously with indomethacin restored the effect of indirect stimulation. 3 The pretreatment of the preparation with guanethidine or a-methyl-p-tyrosine prevented the inhibitory effect of indomethacin on indirectly evoked contractions. Prostaglandin E2 addition to such preparations considerably augmented both types of contraction. 4 The stimulation of non-cholinergic, non-adrenergic inhibitory nerves in the taenia coli and ileum preparations evoked hyperpolarization and relaxation of the preparations followed by action potentials and contraction. These responses were not changed by indomethacin pretreatment and prostaglandin E2, but rebound contraction was sometimes augmented by the prostaglandin. 5 Two mechanisms for the effects of prostaglandin E2 are suggested: a direct effect on smooth muscle, and an indirect action through the sympathetic nerves which by release of noradrenaline affect the acetylcholine release from parasympathetic nerve endings.

The Effects of Non‐steroidal Anti‐inflammatory Drugs on Cholinergic and Histamine‐induced Contractions of Guinea‐pig Isolated Ileum

“…Ehrenpreis, Greenberg & Belman (1973) and Bennett, Eley & Stockley (1975) found that indomethacin (40,g/ml) substantially reduced contractions of the longitudinal muscle of guinea-pig isolated ileum in Krebs solution to nerve stimulation with transmural electrical pulses. Kadlec, Masek & Seferna (1974) obtained similar results with indomethacin (0.36 jg/ml) in a modified Krebs solution. The difference in the concentration of indomethacin needed depends on the composition of the bathing solution (Bennett et al, 1975).…”

“…The inhibitory effect of indomethacin on electricallyinduced contractions of the guinea-pig ileum described by Ehrenpreis et al (1973), Kadlec et al (1974 and Bennett et al (1975) was confirmed by us and extended to 10 other acidic NSAID which inhibit prostaglandin synthesis (Flower, 1974) but have different chemical structures.…”

A possible role for prostaglandins in the expression of morphine dependence in guinea‐pig isolated ileum

“…It has been suggested by Ehrenpreis et al (1973) that prostaglandins can reverse the inhibition of the electrically evoked twitch of guinea-pig ileum produced by morphine and this is consistent with the results of Kadlec et al (1974) who showed that prostaglandins can increase the electrically stimulated release of acetylcholine in guinea-pig ileum. Okpako & Taiwo (1984) have demonstrated that cyclooxygenase inhibitors can inhibit electrically evoked release of acetylcholine from myenteric plexus longitudinal muscle strip preparations.…”

A Possible Negative Feedback Control of Excitatory Transmission via Prostaglandins in Canine Small Intestine

“…These reports and the present study, suggest that there are species differences in the effects of prostaglandin on the intestinal muscle. Kadlec, Masek & Seferna (1974) considered that the potentiating effect of prostaglandin on the contraction induced by nerve stimulation in the longitudinal muscle of guinea-pig ileum was due to inhibition of adrenergic nerves which normally inhibit cholinergic transmission.…”