Pituitary responsiveness to 44 amino acid human pancreatic growth hormone releasing factor was tested under conditions of euglycaemia and hyperglycaemia in six normal subjects. A 100 micrograms dose of growth hormone releasing factor was given at a fasting blood glucose of 5.1 +/- 0.4 mmols/l (mean +/- S.D.), and at a blood glucose level of 10.9 +/- 1.5. Under conditions of hyperglycaemia, the GH response to releasing factor was significantly depressed when compared to results obtained at fasting blood glucose (n = 6, t = 3.902, P = 0.0114). This is in keeping with the hypothesis that hyperglycaemia, mediated by the hypothalamus, causes decreased pituitary sensitivity to natural growth hormone releasing hormone.

Global abdominal visceral ischemia leads to profound cardiovascular reflex adjustments. However, the separate contributions of the celiac artery and superior mesenteric artery (SMA) vascular beds to this reflex are unknown. Accordingly, we compared the effects of single and combined occlusions of these vessels on blood pressure (BP) in anesthetized cats. Tissue mass and pH of selected organs, regional blood gases, pH, and lactate also were measured as potential contributing factors. Occlusion of the SMA or celiac artery produced significantly (P < 0.05) different increments in BP (30 +/- 4 vs. 18 +/- 4 mmHg, respectively). Combined occlusion of the two vessels augmented BP by 53 +/- 12 mmHg, a significantly greater increase than during celiac ligation. Venous lactate levels increased significantly during SMA, but not celiac, occlusion, and the decline in venous pH was significantly greater in the SMA than in the celiac vascular bed (-0.20 +/- 0.03 vs. -0.08 +/- 0.02 pH units, P < 0.05, respectively). The decline in tissue pH of SMA-perfused organs during SMA occlusion was significantly greater than in celiac-perfused organs during celiac occlusion. Conversely, tissue mass subserved by the celiac artery was significantly greater than that subserved by the SMA (182 +/- 27 vs. 131 +/- 17 g, respectively). These data suggest that the larger cardiovascular reflex produced by SMA occlusion compared with celiac occlusion may be related to a greater increase of lactic acid concentration in tissue supplied by the SMA. In addition, the large reflex increase in BP produced by combined occlusion of these vessels is an additive effect, presumably related to larger organ mass and recruitment of more sensory nerve fibers.

Adenosine can induce visceral hyperalgesia and decrease oesophageal distensibility in humans. These evoked sensorimotor changes are similar to those described in patients with functional oesophageal (non-cardiac) chest pain. Thus, adenosine modulates oesophageal sensorimotor function and may play a role in the pathogenesis of functional chest pain.

Ischemically sensitive visceral sympathetic nerve fibers, which are thought to represent the afferent limb of a strong cardiovascular pressor reflex, can be stimulated by exogenously applied bradykinin (BK). During ischemia, BK also is known to be produced locally and to serve as an endogenous stimulus for activation of ischemically sensitive nerve endings. It is unclear, however, whether ischemically induced BK production is sufficient to elicit a reflex cardiovascular response. Accordingly, femoral arterial and venous catheters were positioned in anesthetized cats, and the superior mesenteric and celiac arteries were isolated for placement of snare occluders. After dual occlusion of these arteries (20 min), one of two chemically dissimilar specific kinin B2(BK2) receptor antagonists, HOE-140 (30–40 μg/kg iv, n = 8) or NPC-17731 (30–40 μg/kg iv, n= 11), was administered and dual occlusion was repeated. The reflex rise of mean arterial blood pressure (BP) of 16 ± 3.7% was significantly ( P < 0.05) reduced by HOE-140 to 8.4 ± 2.0%. NPC-17731 similarly attenuated the reflex BP increment from 13 ± 1.2 to 6.2 ± 1.6% ( P < 0.05). In a separate set of control animals the first and second periods of ischemia induced reflex BP increments that did not differ significantly (16 ± 2.7 and 16 ± 5.7%, respectively). Qualitatively similar decrements of the BP response were produced by the BK2 receptor antagonists in two additional groups in which blood flow to the superior mesenteric and celiac arteries was diverted to a venous reservoir to eliminate the initial transient (mechanically induced) rise in BP associated with artery ligation that is known not to be associated with the reflex response. These results indicate that the stimulation of BK2 receptors on visceral afferent nerves by BK is responsible, at least in part, for the reflex cardiovascular response during visceral ischemia.

Background Esophageal sensation is commonly assessed by barostat-assisted balloon distension (BBD) or dynamic balloon distension (DBD) technique, but their relative merits are unknown. Our aim was to compare the usefulness and tolerability of both techniques. Methods Sixteen healthy volunteers (M/F= 6/10) randomly underwent graded esophageal balloon distensions, using either BBD (n=8) or DBD (n=8). BBD was performed by placing a 5 cm long highly compliant balloon attached to a barostat, and DBD by placing a 5 cm long balloon attached to a leveling container. Intermittent phasic balloon distensions were performed in increments of 6 mm Hg. Sensory thresholds and biomechanical properties were assessed and compared. Key Results Sensory thresholds for first perception (mean ± SD; 21 ± 6 vs. 21.2 ± 5, mm Hg, p=0.9), discomfort (38 ± 8 vs. 35 ± 9, p=0.5), and pain (44 ± 4 vs. 45 ± 3, p=0.7) were similar with BBD and DBD techniques. However, more subjects tolerated DBD (7/8, 88%) when compared to BBD (4/8, 50 %). Forceful expulsion of balloon into stomach (n=4), pulling around the mouth (n=4), chest discomfort (n=2) and retching (n=2) were overlapping reasons for intolerance with BBD. Esophageal wall distensibility was similar with both techniques. Conclusions Both techniques provided comparable data on biomechanical properties. However, DBD was better tolerated than BBD for evaluation of esophageal sensation. Hence, we recommend DBD for performing esophageal balloon distension test.