A role for alpha-adrenergic receptors in abnormal insulin secretion in diabetes mellitus. (9/69)

To determine whether endogenous alpha-adrenergic activity contributes to abnormal insulin secretion in nonketotic, hyperglycemic, diabetic patients, alpha-adrenergic blockade was produced in normal and diabetic subjects. The diabetics had a significantly (P less than 0.01) greater increase in circulating insulin 1 h after an intravenous phentolamine infusion than did the normal subjects. During the phentolamine infusion, there was also a significant augmentation of acute insulin responses to intravenous glucose (20 g) pulses in normal subjects (P less than 0.05) and diabetics (P less than 0.02); this augmentation was fivefold greater in the diabetics. Simultaneous treatment with the beta-adrenergic blocking agent, propranolol, did not alter these findings. Thus a role for exaggerated endogenous alpha-adrenergic activity in abnormal insulin secretion of the diabetic subjects is suggested. To determine whether this alpha-adrenergic activity might be related to elevated circulating catecholamines, total plasma-catecholamine levels were compared in normal and nonketotic diabetic subjects given intravenous glucose pulses. These levels were significantly greater (P less than 0.02) in the diabetic compared to the normal group before the glucose pulse, and increased significantly in both groups (P less than 0.02 and less than 0.001, respectively) after the pulse. These data suggest that excessive catecholamine secretion may lead to an abnormal degree of endogenous alpha-adrenergic activity, which contributes to defective insulin secretion in diabetic subjects.  (+info)

Neuronal locus and cellular signaling for stimulation of ileal giant migrating and phasic contractions. (10/69)

We investigated the neuronal locus, the role of PKC activation, and utilization of extracellular Ca(2+) and intracellular Ca(2+) release in smooth muscle cells for the generation of giant migrating contractions (GMCs) and rhythmic phasic contractions (RPCs) in intact normal and inflamed canine ileum. Calcitonin gene-related peptide (CGRP), administered close intra-arterially, stimulated GMCs at higher doses and RPCs at smaller doses. These effects were blocked by prior close intra-arterial infusions of CGRP(8-37), atropine, hexamethonium, and TTX but not by tachykinin, serotonin, and histaminergic receptor subtype antagonists. Both types of contractions were blocked by verapamil in normal and inflamed ileums. Dantrolene and ruthenium red blocked only the RPCs in normal ileum but blocked both GMCs and RPCs in the inflamed ileum. PKC inhibition by chelerythrine blocked GMCs only in inflamed ileum but blocked RPCs in both normal and inflamed ileums. The inhibition of phospholipase C by neomycin blocked both RPCs and GMCs in normal and inflamed ileums. In conclusion, acetylcholine is the common neurotransmitter for the stimulation of both GMCs and RPCs, but the signaling cascades for their stimulation are partially divergent, and they differ also in the normal and inflamed states.  (+info)

Overexpression of eNOS in RVLM improves impaired baroreflex control of heart rate in SHRSP. Rostral ventrolateral medulla. Stroke-prone spontaneously hypertensive rats. (11/69)

We previously demonstrated that the overexpression of endothelial nitric oxide synthase (eNOS) in the rostral ventrolateral medulla (RVLM) decreases blood pressure, heart rate (HR), and sympathetic nerve activity and that these effects are enhanced in stroke-prone spontaneously hypertensive rats (SHRSP). The aim of this study was to determine if an increase in NO production in the RVLM caused by the overexpression of eNOS improves the impaired baroreflex control of HR in SHRSP. We transfected adenovirus vectors encoding eNOS (AdeNOS) into the RVLM of SHRSP or Wistar-Kyoto rats (WKY). Mean arterial pressure and HR were measured by a radio-telemetry system in the conscious state. Reflex changes in HR were elicited by intravenous infusion of either phenylephrine, sodium nitroprusside, or hydralazine at day 7 after the gene transfer. The maximum gain of the baroreflex control of HR was significantly decreased in SHRSP compared with WKY. Overexpression of eNOS in the RVLM of SHRSP improved the impaired maximum gain of the baroreflex control of HR. After treatment with atropine, the maximum gain was still significantly greater in SHRSP in the AdeNOS-transfected group than in the nontransfected group, although it was decreased in both groups. In contrast, after treatment with metoprolol, the maximum gain did not differ between the two groups. These results indicate that an increase in NO production in the RVLM improves the impaired baroreflex control of HR in SHRSP and that these effects may have resulted from a cardiac sympathoinhibitory effect of NO in the RVLM of SHRSP.  (+info)

Hypotensive effect of push-pull gravitational stress occurs after autonomic blockade. (12/69)

The "push-pull" effect denotes the reduced tolerance to +Gz (hypergravity) when +Gz stress is preceded by exposure to hypogravity, i.e., fractional, zero, or negative Gz. Previous studies have implicated autonomic reflexes as a mechanism contributing to the push-pull effect. The purpose of this study was to test the hypothesis that nonautonomic mechanisms can cause a push-pull effect, by using eye-level blood pressure as a measure of G tolerance. The approach was to impose control (30 s of 30 degrees head-up tilt) and push-pull (30 s of 30 degrees head-up tilt immediately preceded by 10 s of -15 degrees headdown tilt) gravitational stress after administration of hexamethonium (10 mg/kg) to inhibit autonomic ganglionic neurotransmission in four dogs. The animals were chronically instrumented with arterial and venous catheters, an ascending aortic blood flow transducer, ventricular pacing electrodes, and atrioventicular block. The animals were paced at 75 beats/min throughout the experiment. The animals were sedated with acepromazine and lightly restrained in lateral recumbency on a tilt table. After the onset of head-up tilt, the magnitude of the fall in eye-level blood pressure from baseline was -27.6 +/- 2.3 and -37.9 +/- 2.7 mmHg for the control and push-pull trials, respectively (P < 0.05). Cardiac output fell similarly in both conditions. Thus a push-pull effect attributable to a rise in total vascular conductance occurs when autonomic function is inhibited.  (+info)

Autonomic nervous responses according to preference for the odor of jasmine tea. (13/69)

The effect of jasmine tea odor on the autonomic nervous system was investigated by a power spectral analysis of the heart rate variability. We assigned eight volunteers to two groups with either a predilection for or antipathy toward the jasmine tea odor. We tested both high- and low-intensity jasmine tea odors. The low-intensity odor was produced by diluting 20-fold the jasmine tea used for the high-intensity odor test. The low-intensity odor produced an increase in parasympathetic nervous activity in both the predilection and antipathy groups. The high-intensity odor produced an increase in parasympathetic nervous activity in the predilection group, but an increase in sympathetic nervous activity in the antipathy group. The odor of Chinese green tea, a basic ingredient of jasmine tea, produced no effects similar to those of the jasmine tea odor. These results suggest that the jasmine tea odor activated the parasympathetic nerve, whereas the higher-intensity odor activated the sympathetic nerve in those subjects who disliked the odor.  (+info)

Effect of experimental diabetes, food deprivation and genetic obesity on the sensitivity of pithed rats to autonomic agents. (14/69)

1 The sensitivities of alloxan and streptozotocin diabetic and hereditary obese pithed rats to acetylcholine, isoprenaline and noradrenaline were compared to those of controls. 2 Blood pressure and heart rate recordings made before dosing was started showed the streptozotocin-treated animals to have a significantly reduced heart rate and increased pulse pressure as compared with controls. 3 Both diabetic groups were found to have reduced sensitivities to the pressor effect of noradrenaline, the depressor effect of acetylcholine, the positive chronotropic and inotropic effect of isoprenaline and the reduction in diastolic pressure induced by isoprenaline. The reduction in sensitivity was generally much greater in the streptozotocin diabetic animals. 4 The genetically obese rats were found to have similar sensitivities to all three agents as did their non-obese litter mates. 5 When either diabetic group was deprived of food for 24 h preceding the tests the sensitivities were found to be raised significantly towards normal in almost all cases. 6 The results are contrasted with previous in vitro results and possible causative metabolic factors discussed. It is suggested that sensitivity changes are unevenly distributed within the cardiovascular system.  (+info)

Pharmacological properties of pempidine (1:2:2:6:6-pentamethylpiperidine), a new ganglion-blocking compound. (15/69)

Pempidine (1:2:2:6:6-pentamethylpiperidine) is a long-acting ganglion-blocking compound which is effective by mouth. By intravenous injection it has a similar potency to hexamethonium on the preganglionically stimulated nictitating membrane of the cat. The compound blocks the effects of intravenous nicotine and of peripheral vagal stimulation on the blood pressure; it also causes dilatation of the pupil after removal of the sympathetic innervation. On the guinea-pig ileum, the predominant effect of the compound is to inhibit nicotine contractions. Pempidine is well absorbed from the gastro-intestinal tract as judged by (a) the low ratio (6.9) of oral to intravenous toxicities, (b) the rapid development of mydriasis in mice after oral administration of small doses, and (c) the rapid onset of hypotension when the compound is injected directly into the duodenum of anaesthetized cats. Other actions include neuromuscular paralysis of curare-like type when large doses of the compound are injected intravenously and central effects such as tremors which occur with near toxic doses. In cats with a low blood pressure, large intravenous doses have a slight pressor action.  (+info)

The persistence of a depressor response to oxytocin in the fowl after denervation and blocking agents. (16/69)

The effects of oxytocin and vasopressin on the blood pressure of the fowl have been studied after surgical or chemical interruption of parts of the central and peripheral nervous systems, and after the administration of stilboestrol and progesterone. An augmented and prolonged depressor response to oxytocin was seen after atropine, bretylium, tetraethylammonium or decapitation, but not after decerebration, dihydroergotamine or dibenamine. There was a tendency for the pressor action of vasopressin to disappear after decapitation, decerebration, and all the blocking agents used, except tetraethylammonium. The differences between these results and those which have been obtained in rats are discussed.  (+info)