PubMed Health⌕ Search

Biomedical subjects

H Ahlman

Publications and source records attributed to H Ahlman.

At least 199 records · Page 11Linked to original sources
PubMed1980

The peptidergic neural control of the feline pylorus.

By immunohistochemistry the three neuropeptides enkephalin, substance P, and VIP were all localized to numerous nerve fibers in the smooth muscle layer and the myenteric plexus of the feline pylorus. The motor activity of the pylorus was studied by recording changes in the volume flow of body-warm saline through the sphincter at constant perfusion pressure in anesthetized cats. Efferent electric stimulation of the cervical vagi (8 V; 5 ms; 8 Hz) elicited a noncholinergic, nonadrenergic pyloric contraction, which was blocked by infusion of the opiate receptor antagonist naloxone. The peptides were injected into a regional gastric artery to the pylorus antrum. Enkephalin and substance P in micronanomolar doses resulted in a prompt contraction of 3 - 5 min duration. Equimolar doses of naloxone blocked the enkephalin-induced contraction, and atropine blocked the SP contraction. On the other hand, VIP caused a prompt dilatation, which could not be blocked in this study. Altogether the findings suggest a peptidergic motor control of the feline pylorus using several transmission mechanisms.

Animals↗
PubMed1980

The effects of adrenergic antagonists on the serotonin levels of feline enterochromaffin cells after splanchnic nerve stimulation.

Cut splanchnic nerves were stimulated electrically at the preganglionic level in efferent direction in anesthetized cats with the adrenals ligated bilaterally. A significant decrease of the intracellular serotonin (5-HT) levels in populations (n = 20) of individual enterochromaffin cells (EC) in the mucosa from three different levels of the small intestine (distal duodenum, mid-jejunum and terminal ileum) was obtained. The intracellular 5-HT levels before and after stimulation were studied cytofluorimetrically in biopsies treated according to the Falck-Hillarp technique. One group of cats was pretreated with propranolol prior to stimulation. This prevented the decrease in fluorescence intensity effectively. Two other groups of cats were pretreated with phenoxybenzamine or phentolamine. These drugs also blocked the expected decrease in fluorescence intensity in 7 of 8 cats. In some biopsies there was an increased fluorescence intensity after nerve stimulation in cats given propranolol or phentolamine even though the drugs themselves had no intrinsic effects on the fluorescence intensity in control animals. It is concluded that efferent electrical stimulation of the splanchnic nerves can cause a release of 5-HT from gut EC by an adrenergic mechanism.

Animals↗
PubMed1980

Evidence for vagal enkephalinergic neural control of the feline pylorus and stomach.

The atropine- and guanethidine-resistant contraction of the cat pyloric sphincter induced by efferent stimulation of the cervical vagi, was studied with a new method for measuring transpyloric flow. The pyloric contraction was blocked in a dose-dependent manner by the opiate antagonist naloxone infused intraarterially to the pyloric region. Local intraarterial injection of morphine or enkephalinamide elicited a pyloric and gastric contraction. Leu- and met-enkephalin intraarterially elicited a pyloric contraction and a gastric relaxation. These effects could be prevented or reversed by naloxone. Immunohistochemical studies revealed a particularly rich enkephalinergic innervation of the pylorus with dense networks of varicose nerve fibers with enkephalin-like immunoreactivity both in the circular smooth muscle layer and in the myenteric plexus. Furthermore, many cell bodies of the myenteric plexus with enkephalin-like material were demonstrated. The corpus-antrum was sparsely innervated by enkephalin-like nerves to the circular muscle layer and only few immunoreactive cell bodies were observed in the myenteric plexus. These results together suggest a vagal control of the feline pylorus and stomach mediated via enkephalinergic neurons.

Animals↗
PubMed1979

The effects of splanchnic nerve stimulation on the plasma levels of serotonin and substance P in the portal vein of the cat.

The blood levels of serotonin (5-HT) and substance P (SP) in the portal vein were studied after splanchnic nerve stimulation in the cat. The portal levels of both substances were studied before, during and after splanchnic nerve stimulation. There was a twofold increase in 5-HT during stimulation whilst the SP concentration remained unchanged. These results suggest that the nervous control of the amine release into the portal stream and the mechanism that regulates the release of the polypeptide is not the same.

Animals↗
PubMed1979

The effect of transmural field stimulation on the serotonin content in rat duodenal enterochromaffin cells--in vitro.

The effect of transmural field stimulation (TFS)--in vitro--on the sertonin (5-HT) content in enterochromafffin cells (EC) in rat duodenum was studied with a cytofluorimetric method. TFS caused a significant 25% decrease of 5-HT in EC. The presence of tetrodotoxin or d,1-propranolol in the stimulation bath antagonized the effect of TFS. In biopsies from rats pretreated with 6-OH-dopamine TFS had no effect of the 5-HT content in EC. The results of the present study strongly suggest, that the TFS induced decrease in 5-HT content is due to a direct neural, probably beta-adrenoceptor mediated, influence on the EC.

Adrenergic Fibers↗
PubMed1979

The vagal control of the feline pyloric sphincter.

In acute experiments on cats in chloralose anesthesia the effects of efferent and afferent electrical stimulation of the cervical vagi on an applied constant flow of saline through the feline pylorus was studied. The motor activity of the stomach was recorded simultaneously with a volume recording technique. Efferent cervical vagal stimulation caused a decrease in the transpyloric flow and an increased gastric motor activity. In a few animals the decreased transsphincteric flow was preceded by a short period of increased flow. When the transpyloric flow was reduced by splanchnic nerve stimulation or a noradrenaline infusion, vagal nerve stimulation induced an increased flow through the pylorus indicating the presence of relaxatory fibres to the pylorus within the vagi. Electrical stimulation of the central end of the ipsilateral vagal nerve in the neck, with the contralateral vagal verve left intact, resulted in a decreased transpyloric flow and relaxation of the stomach. This response could be induced with or without intact splanchnic nerves, and disappeared when the intact contralateral vagus was cut. It is concluded that the vagi mediate both excitatory and inhibitory fibres to the pyloric sphincter in the cat. A vago-vagal excitatory reflex to the pylorus can be elicited by afferent vagal nerve stimulation together with a vago-vagal relaxatory response of the stomach.

Afferent Pathways↗
PubMed1979

The effect of propranolol on the serotonin concentration in the portal plasma after vagal nerve stimulation in the cat.

Efferent cervical vagal nerve stimulation in the cat caused a marked increase of the portal plasma 5-HT concentration. This increase was more than two-fold within 15 min of stimulation. After cessation of stimulation portal plasma 5-HT returned to basal levels within 10 min. Treatment with the beta-adrenoceptor antagonist propranolol, in various doses (0.1-2 mg/kg b.wt.), did not abolish but significantly reduced the response to vagal stimulation, particularly during the final part of the stimulation period. The results confirm the existence of a beta-adrenoceptor-mediated release of 5-HT, but also suggest that other mechanisms for 5-HT release may be involved in the response on vagal nerve stimulation.

Adrenergic beta-Antagonists↗
PubMed1979

Substance P-, VIP-, and enkephalin-like immunoreactivity in the human vagus nerve.

The human vagus nerve has been investigated for the presence of substance P (SP), vasoactive intestinal polypeptide (VIP), and enkephalin (ENK) using immunohistochemistry. After 0.5-4 hr of nerve ligation during surgical operations two right thoracic main truncs, two anterior subdiaphragmal trunks, and four anterior nerves of Latarjet were found to contain accumulation of immunoreactive material in nerve fibers above the ligation. Very high numbers of SP-, medium numbers of ENK-, and low number of VIP-immunoreactive fibers were seen. The relative proportions were similar at all levels studied. These data thus indicate the presence and axonal transport of SP-, ENK-, and VIP-like peptides in the human vagus nerve. Our observations in humans correlate well with results obtained from other species. Thus gastrointestinal vagal sensory mechanisms may be mediated by SP (and possibly VIP) and some motor mechanisms by ENK.

Endorphins↗
PubMed1978

Cancer risk in extensive ulcerative colitis.

Two hundred thirty-four patients with extensive ulcerative colitis from the city of Göteborg, Sweden have been followed up and the cumulative risk of development of cancer of the large bowel was estimated. These patients constitute all persons in this region who developed an extensive ulcerative colitis between 1951 and 1974. All patients were followed up until December 1975. The mean observation time was 8.5 years, median value six years. Fifteen patients developed carcinoma of the large bowel. Five of the 15 patients were still alive in December 1975. The expected number of colorectal carcinomas in a matched reference group was 0.49. The cumulative incidence of carcinoma 25 years after the onset of colitis for the whole group of patients was 34% and for those who developed the disease before 25 years of age it was 43%.

Adult↗
PubMed1978

The release of serotonin from rat duodenal enterochromaffin cells by adrenoceptor agonists studied in vitro.

The serotonin (5-HT) content of enterochromaffin cells (EC) was studied by a cytofluorimetric method in biopsies from rat duodenal mucosa after in vitro incubation with different adrenoceptor agonists and antagonists and acetylcholine (ACh). Noradrenaline (NA), Adrenaline (A) and Isoprenaline (IP) caused a decrease of 5-HT in EC down to 40--60% and for NA and A this effect was concentration-dependent. The effect was antagonized by d,1-propranolol but not by d-propranolol, metoprolol, phentolamine or phenoxybenzamine indicating that the 5-HT release from EC is probably mediated via a true beta-adrenoceptor mechanism possibly of the beta2 type. ACh also decreased the 5-HT content of EC but was much less potent than the adrenergic substances. Dopamine (DA) had no effect.

Acetylcholine↗