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The role of bombesin in the regulation of gastrin and somatostatin secretion was examined using an isolated vascularly perfused rat stomach preparation. Bombesin caused a biphasic, dose-dependent increase in gastrin and bombesin secretion. Neither somatostatin nor gastrin secretion was inhibited by atropine. The maximal gastrin response to bombesin (198 +/- 75% above basal levels) was less than one-half the maximal response to methacholine (462 +/- 94%). It was postulated that the concomitant release of somatostatin, in part from antral mucosa, attenuated the gastrin response to bombesin; the notion was tested with somatostatin antiserum. A 50- to 100-fold excess of sheep somatostatin antiserum augmented significantly the maximal gastrin response to bombesin by 966% in the initial peak period and by 532% in the plateau period; the response in the plateau period was not significantly different from the maximal response to methacholine. Methacholine stimulated the release of gastric bombesin also, but the exact cellular origin of the peptide could not be ascertained. On the basis of these results and of the topography of antral bombesin neurons and somatostatin D cells, a model for the neural (via bombesin) and paracrine (via somatostatin) control of gastrin secretion within the antrum is proposed.

It is well known that the plant kingdom contains numerous bioactive substances affecting the regulation of reproduction. The present study was undertaken to examine the putative contraceptive effects of three traditional plant extracts from Côte d'Ivoire Pharmacopea. It concerns Afrormosia laxiflora (Papilionacea), Pterocarpus erinaceus (Papilionacea) and Cola nitida (Sterculiacea) stem bark. Data showed that treatment of rats with these plant extracts induced ovulation and oestrous cycle blockade at the dioestrous II stage. The analysis of the principal hormones involved in oestrous cycle regulation showed that the plant extracts decreased gonadotropin release (both LH and FSH). In fact, A. laxiflora, P. erinaceus and C. nitida extracts inhibited gonadotropin release as an antiestrogen-like substance.

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