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The effect of tetragastrin and histamine on the adenylate cyclase activity of the rat gastric mucosa was examined in vitro. Tetragastrin and histamine were demonstrated to stimulate the activity of the enzyme in question. The antagonist of histamine H2-receptors, cimetidine inhibits the stimulatory effect of histamine in vitro and activates tetragastrin stimulation of the adenylate cyclase activity. It is suggested that tetragastrin and histamine activate adenylate cyclase of the rat gastric mucosa via different receptors.

A study was made of the action of C-terminal tetrapeptide cholecystokinin (CCK-4) on the secretory function of A-, B- and D-cells of the islets of Langerhans and on the lactotropic function of the hypophysis. Intravenous injection into rats of CCK-4 in doses of 5 and 50 micrograms/kg bw resulted within 2 min in increased blood immunoreactive insulin. Tetrapeptide also exerted a stimulant dose-dependent action on the function of insulin-, glucagon- and somatostatin-secreting pancreatic cells of the pancreatic islets in culture at concentrations ranging within 10(-9)-10(-6)M. When given in the same doses CCK-4 did not affect basal or dopamine-inhibited prolactin secretion by cultured adenohypophyseal cells. It is concluded that CCK-4 stimulates insulin, glucagon and somatostatin secretion by direct contact with target cells.

Within 15 to 30 days after right unilateral subdiaphragmal vagotomy, resection of the anterior liver nervous plexus and mucosoantrumectomy in dogs, the gall bladder contractile function weakens and its adsorbing and concentrating functions are considerably impaired. Within a year these disturbances become less obvious and tend to normalize. These disturbances prove the local hormonal and the autonomic neural control in the gall excreting system. In the digestion phase, neurotensin, angiotensin and enkephalin inhibited the gall bladder motility. This effect was facilitated after sympathectomy and vagotomy due to non-adrenergic inhibitory influences on the gall bladder. Enkephalin might be capable of a direct effect upon the smooth muscles, particularly upon the muscle fibers of the gall bladder's neck. Pentagastrin was found to exert a biphasic effect on the Oddi sphincter tone: exciting the sphincter's circular muscles and inhibiting them with non-cholinergic and non-adrenergic neurons.

In chronic experiments on dogs, the motor function and electric activity of the smooth muscles of the stomach, duodenum, and gall-bladder were electrophysiologically and roentgenologically studied.

A study was made of the effect of the low-molecular neuropeptides, leu- and met-enkephalins, thyroliberin (TRH), the C-end tripeptides, gastrin (MAF) and oxytocin (MIF) on the content of biogenic monoamines and their metabolites and on the production of humoral antibodies to sheep red blood cells. The action of the peptides enumerated was compared to that of the peptide immunostimulant, tuftsin. All the peptides (upon intraventricular administration) with the exception of tuftsin affect the content of brain biogenic monoamines or their metabolites. Moreover, upon intravenous injection the neuropeptides under study except met-enkephalin exert a modulating action on the immune response pattern and intensity Leu-enkephalin, MIF and MAF have immunostimulant activity similar to tuftsin. TRH given in high doses (100 and 150 mg/kg) provokes almost a two-fold decrease in the antibody titer. This peptide has an immunosuppressant effect when administered both intravenously and intracisternally. It is suggested that neuro- and immunomodulator effects have much in common at the level of cell receptors.

The effect of some tripeptides, which are fragments of peptide hormones, and their analogs on the content of biogenic monoamines (BM) from albino mice brain was studied. It was found that thyroliberin, melanostatin and the C-terminal tripeptide of gonadoliberin activate the dophaminergic (DA-ergic) system in the forebrain of mice treated with reserpine or haloperidol, whereas the C-terminal tripeptide of gastrin acts as a synergic blocker of the DA receptors. The N-terminal tripeptides (with and without the amido group) do not affect the content of BM. No effect of the tripeptides was observed in intact animals. It is assumed that the agonistic or antagonistic effect of the tripeptides on BM is due to certain structural peculiarities of the tripeptides, e.g. the presence of the C-terminal amido group and their endogenous nature.

In dogs with fistulas in fundal and antral parts of the stomach and in the proximal part of jejunum, subcutaneous and i.v. administration of pentagastrin and i.v. administration of cholecystokinin caused reciprocal reactions in the stomach: pentagastrin suppressed the motility of fundal part and activated the contractions of antral part, whereas cholecystokinin activated the contractions of fundal part and suppressed the motility of antral part of the stomach. Excepting a more complex character of pentagastrin and cholecystokinin effects on the jejunum contractions, the responses were reciprocal as well. Pentagastrin exerts mainly a suppressing effect whereas cholecystokinin--an activating one. Possible biological significance of the hormones interactions while maintaining evacuatory function of the stomach, is discussed.

An x-ray method modified by the authors was employed in 40 patients with peptic ulcer of the duodenum to examine the effect of pentagastrin and histamine on the rate of gastric evacuation of x-ray capsules 3, 5 and 10 mm in diameter taken with the trial breakfast. It was established that pentagastrin inhibits gastric evacuation (P less than 0.05) mainly at the expense of retention of the egress from it of the capsules 10 mm in diameter (P less than 0.05). Administration of histamine does not exert any essential effect on the rate of gastric evacuation. Administration of gastrin following cimetidine also brings about an inhibition of gastric evacuation (P less than 0.05) largely at the expense of retention of evacuation of the capsules larger in diameter. It is concluded that inhibition of gastric evacuation after gastrin administration occurs at the expense of an elevation of the tone of the pyloric sphincter. It is suggested that in the mechanism of the inhibitory action of pentagastrin, the level of hydrochloric acid secretion and H2 receptors of histamine do not play any important role. The inhibitory effect of pentagastrin is likely to be caused by an elevation of the somatostatin level.

The ultrastructure of the gastric parietal cells was studied in rats affected by a genetic inductor of the hydrochloric acid secretion and its mediators in this process - histamine and cyclic 3', 5'-adenozinemonophosphate playing the role of the enzyme activators. All these stimulators caused similar changes in the cell structure. The square surface of the intracellular secretory tubules was shown to become 2,5 times larger, and that of the canaliculi - vesiculoid elements which seemed to be the cell membrane depot became 2,5 times less. It may be supposed that the gastric mucosa parietal cells are not the target-cells for pentagastrine (gastrine).