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Biomedical subjects

G Bertaccini

Publications and source records attributed to G Bertaccini.

At least 163 records · Page 9Linked to original sources
PubMed1980

Action of caerulein on gastric emptying of the conscious rat.

Caerulein was shown to delay gastric emptying in conscious rats in a dose-dependent fashion. The threshold dose was about 0.05 mug/kg by the intraperitoneal route. Maximum effect was obtained with 5 mug/kg. Neutralization of acidity or reduction of gastric juice by mean of NaHCO3 or cimetidine, respectively, did not modify the effect of the peptide. Chlorpheniramine was similarly ineffective. The effect of caerulein on gastric emptying was most probably connected with a strong contraction of the gastroduodenal junction previously observed in different experimental conditions and was not affected by H1- or H2-histamine antagonists. The C-terminal heptapeptide of cholecystokinin behaved quite similarly to caerulein. The present study emphasizes the close parallelism between results obtained in the in situ stomach preparation of anaesthetized rats and gastric emptying in conscious animals.

Animals↗
PubMed1979

Histamine receptors in the guinea pig ileum.

Histamine and some related compounds acting selectively on H2-or H1 receptors were tested for their ability to contract the guinea pig ileum, in the usual whole ileum preparation and in the longitudinal muscle preparation. The concentrations elicited by histamine in both kinds of preparations were not potentiated by cimetidine or metiamide and were not inhibited by administration of H2 receptor selective agonists in doses which were subthreshold for contracting the guinea pig ileum; higher doses of the H2 agonists could actually potentiate the effect of histamine. The results obtained suggest that H2 receptors with relaxing effect do not occur in the guinea pig ileum or at least that they are not involved in the contraction of the longitudinal muscle layers. The possibility that a sub-type of H2 receptors with properties different from those of the "classical" H2 receptors so far known, exists in the guinea pig ileum, cannot be excluded.

Animals↗
PubMed1979

Action of histamine receptor agonists and antagonists on the rat uterus.

1 Histamine and a series of compounds acting selectively on H1- and H2-receptors were tested on the isolated oestrous uterus of the rat. 2 Histamine had a dose-dependent inhibitory effect on the contractions elicited by acetylcholine. This action was unaffected by H1-blockers but was competitively inhibited by H2-blockers. The H1-selective agonist, 2-(2-aminoethyl)thiazole was ineffective at doses 100 times greater than those of histamine. Conversely, all the H2-agonists showed activity in the order of potency: N'-methylhistamine greater than histamine greater than N'-N'-dimethylhistamine greater than 5-methylhistamine greater than 5-methyl-N'-methylhistamine. Among the non-imidazole compounds, dimaprit had an activity identical to that of histamine, but all the dimaprit-like compounds showed negligible activity. 3 The data obtained suggest that in the rat uterus, (a) the activation of H2-receptors is responsible for the inhibitory effect of histamine and its analogues; (b) the integrity of the histamine molecule seems to be less crucial than that of the dimaprit molecule for the maintenance of the H2-activity, since changes in its structure modify but do not abolish the biological activity as they do in the case of dimaprit; (c) the order of activity of the various H2-receptor agonists is different from that observed in other tissues.

Animals↗
PubMed1979

Effects of cimetidine on the secretion of some pituitary hormones.

Cimetidine infused intravenously into 6 healthy volunteers did not induce significant changes in plasma levels of prolactin (hPRL), thyreotropin (hTSH), gonadotropin (hLH and hFSH) and growth hormone (hGH). Conversely it caused a significant increase in prolactin response to TRH without modifying the hTSH response to thyreotropin-releasing hormone (TRH) and gonadotropin response to gonadotropin-releasing hormone (GnRH). Data obtained in these experiments, together with data reported in the literature, suggest that the amplified prolactin response to TRH observed during cimetidine infusion, is likely to be connected with a blockade of H2-receptors rather than to unspecific actions of cimetidine.

Adult↗
PubMed1979

Prolactin response to TRH after intravenous cimetidine.

Cimetidine administered intravenously to six healthy volunteers caused a significant increase in plasma prolactin response to TRH. The meaning of these results and their relation with the physiological role of histamine H2-receptors in the control of prolactin secretion is discussed.

Blood-Brain Barrier↗
PubMed1979

[Action of TRH on gastrointestinal motility in vitro (author's transl)].

Thyrotropin-releasing hormone (TRH) was studied for its effects on some strips of the gastrointestinal tract in vitro. TRH showed to possess a certain stimulatory activity on proximal segments of the g.i. tract being approximately as effective as histamine. This motor activity of TRH is discussed taking into account a possible physiological role outside the brain.

Acetylcholine↗
PubMed1979

"In vitro" duodenal muscle in the pharmacological study on natural compounds.

In vitro duodenal muscle was found to be a useful tool in the study of natural compounds. In the field of polypeptides rat duodenum was found to be of definite importance to differentiate the bradykinins (which induce relaxation) from the tachykinins (which evoke contractions). Human duodenum both "in vitro" and "in vivo" is relaxed by peptides of the gastrin and cholecystokinin family (like caerulein), whereas it is contracted by bombesin. Dog and cat duodenum is contracted by all the different types of peptides though in various degrees. Guinea pig duodenum is contracted by many peptides and also by histamine and related substances. In this case another differentiation seems to be possible as contraction induced by stimulation of H1 receptors concerns essentially the longitudinal muscle layer whereas stimulation of H2 receptors seems to inhibit the longitudinal contraction because of a contraction of the circular muscle or because of true relaxation of the longitudinal muscle. All the above considerations suggest that a comparative study performed on duodenal muscle of different animals might give useful information in the screening of new natural active compounds of synthetic analogues.

Animals↗
PubMed1979

Antagonistic properties of N-methyl-N'-[2-(5-ethyl-4-imidazolyl-methylthio)ethyl]thiourea.

In the present paper the Authors describe the synthesis and the biological effects of N-methyl-N'-[2-(5-ethyl-4-imidazolylmethylthio)ethyl]thiourea (etiamide). This compound appeared to inhibit, to a certain extent, the effect of histamine on H2-receptors. This inhibition, however, was less pronounced than that elicited by metiamide and in some of the preparations examined appeared to be of the non-competitive type.

Animals↗
PubMed1979

[N-Alkyl-2-(5-methyl-4-imidazolyl)ethylamines. Synthesis and effect on gastric secretion].

Synthesis of some 5-methylhistamines alkylated on the amino group (form. I) together with a new method (C) of obtaining them via 5-methylhistaminol, are described. Both the agonistic and antagonistic pharmacological activities of these methylhistamines were studied in vivo on gastric secretion of different animal species (conscious dogs and cats and anaesthetized rats). The potency of the compounds, as far as the H2-receptor stimulant effect is concerned, was very remarkable in the first members of the series and decreased by increasing the degree of substitution. Independently from their "potency" some members of the series showed an "efficacy" which was actually greater than that of histamine. All the compounds tested were completely devoid of any antagonistic activity against gastric hypersecretion induced by histamine.

Animals↗