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Biomedical subjects

I M Lang

Publications and source records attributed to I M Lang.

84 records · Page 5Linked to original sources
PubMed1983

Mechanisms of the secretory and motor responses of the Brunner's gland region of the intestines to duodenal acidification.

The secretory and motor responses of the Brunner's gland region of the duodenum to luminal acidification were examined in rabbits anesthetized with urethan. Isomotic solutions of sodium chloride (pH 7.2) were perfused continuously through adjacent in situ segments. The pH of the perfusate of the proximal segment was changed to 2.0 for 30 min. Perfusion pressure (motor response) and volume and hexosamine concentration (secretory response) of the effluent were recorded for 3 h. The motor and secretory responses to luminal acidification were examined after intravenous (atropine) or intraluminal (lidocaine) pretreatment. Responses to intravenous infusions of serotonin or secretin were determined, also. Both atropine and lidocaine eliminated the initial motor and secretory responses of the proximal segment. Lidocaine eliminated the delayed secretory response of the distal segment. Serotonin caused initial motor and secretory responses, but secretin caused a delayed secretory response only. These results suggest that duodenal acidification elicits a two-phase increase in Brunner's gland secretion, the first being motor-dependent and the second motor-independent. The initial motor response was mediated by a local reflex composed of cholinergic and perhaps tryptaminergic receptors. The delayed secretory response was mediated by local and nonlocal, possibly hormonal, factors. Increased duodenal motility may provide a vehicle for the rapid expulsion of mucus, and thereby serve an important role in the function of the Brunner's glands.

Acid-Base Imbalance↗
PubMed1983

Cyclobenzaprine effects on locus coeruleus cells in tissue slice.

Tissue slices 400 mu thick were taken from the brain stem, at the level of the locus coeruleus, of 150-250 g Sprague-Dawley rats. Microelectrodes were placed in the locus coeruleus under visual control, and a cell whose discharge rate would decrease with microiontophoretic application of norepinephrine or clonidine was sought. Cyclobenzaprine (CBZ) was then introduced into the perfusion medium at a concentration equivalent to 1 mg/kg body weight of the whole animal. Discharge rates before and during CBZ administration were compared. The six cells with initial discharge rates between 2 and 10 Hz decreased firing with CBZ, whereas the four cells with initial rates between 0.5 and 1.5 Hz increased their rates with CBZ.

Action Potentials↗
PubMed1982

Neural and hormonal control of Brunner's gland secretion.

For many years it has been speculated that the physiological function of Brunner's glands was to secrete mucus to protect the proximal duodenum from the corrosive effects of acidified gastric juice. However the control of Brunner's gland secretion remains an enigma. Some evidence exists which indicates both cholinergic and adrenergic innervation of these glands, but current consensus weighs heavily in favor of a hormonal stimulus for glandular secretion. This is based in part on evidence obtained from denervated Brunner's gland pouches following a feeding stimulus. a number of hormones and hormone-like substances have been investigated as possible mediators in this secretory response, however, no specificity was ever demonstrated. The inability to pinpoint a given substance as a common mediator can be attributed to the fact that most active agents employed also affect duodenal motility. We present evidence that Brunner's gland secretion can be observed to be a diphasic response. The initial, transient response is always observed in the presence of increased duodenal motility. The sustained response does not require duodenal motility and is probably hormonally mediated.

Animals↗
PubMed1982

Chronic administration of naltrexone alters central catecholamine levels but not the development of hypertension in spontaneously hypertensive rats.

The effect of chronic administration of the opiate antagonist naltrexone on the genesis and development of hypertension and correlated changes in central norepinephrine levels was evaluated in spontaneously hypertensive rats and Wistar-Kyoto controls. Capsules of poly-epsilon-caprolactone containing naltrexone in ethyl oleate or ethyl oleate alone were implanted in 4 week old SHR and WKY rats. Naltrexone failed to alter the genesis or magnitude of hypertension developed by the SHR and did not alter heart rates. Blood pressure and heart rate of WKY rats were also unaffected. A significant decrease in midbrain and hippocampal NE levels was observed in SHRs but not in WKYs following naltrexone.

Animals↗
PubMed1982

The effects of chronic administration of naltrexone on appetite and water exchange in rats.

The effects of chronic administration of naltrexone (200 microgram/kg/hr) on appetitive behaviors and renal water and electrolyte excretions were studied in rats. Naltrexone reduced food and water intake, the renal excretions of water and electrolyte excretions were studied in rats. Naltrexone reduced food and water intake, the renal excretions of water and electrolytes, and osmolar clearance. No changes in plasma levels of electrolytes, plasma and urine Na+-K+ ratios, hematocrit ratio, plasma osmolality, the clearances of K+ and Na+, and the reabsorption of solute free water were found. The changes in appetite were compensated for by appropriate changes in renal excretions, resulting in no change in electrolyte balance or water exchange. These observations are discussed in relation to current theories of the role of endorphins in appetite control.

Animals↗
PubMed1981

Effects of chronic administration of naltrexone on appetitive behaviors of rats.

Opioid antagonists have been reported to reduce water and food intake. In the experiments, ingestive behavior was sometimes induced using stressful stimuli. These experiments were conducted to determine the effects of chronic administration of an opioid antagonist on appetitive behaviors of minimally stressed rats. Twelve 4-week old rats were randomly separated into two equal-sized groups, anesthetized with ether, and implanted subcutaneously with poly(epsilon-caprolactone) capsules. One group received naltrexone in the capsules, the other group received vehicle. These capsules released the drug at a rate of approximately 250 microgram/day for over 8 weeks. Gross metabolic behavior (food intake, water intake, urine output, fecal output, and body weight) was monitored for 8 weeks. At three times during the 8 weeks, food deprivation (24 hr)-induced feeding was tested over a period of 60 min. At the end of the eighth week, the animals were subjected to an analgesic test in order to confirm the efficacy of the naltrexone dose. No differences in food intake, body weight, fecal output, or deprivation-induced feeding were observed between the control and naltrexone groups. Water intake and fluid output of the naltrexone group were significantly reduced compared to the control group. These results suggest that endogenous opioids may mediate mechanisms of tonic drinking behavior and cannot be explained as representing effects on stress-induced ingestion.

Analgesia↗