摘要:

Unilateral focal cold blocks in the region of the nucleus tractus solitarius and the dorsal respiratory group of neurons, DRG, of anaesthetized cats consistently caused apneustic‐type breathing. There was no concomitant change in the initial rate of rise of inspiratory activity. The apneustic prolongation of inspiratory duration,T1, was most pronounced in, but was not confined to, the DRG. The apneustic effects were more marked after vagotomy. In cats with intact vagus nerves being given artificial ventilation, focal cooling at certain sites of the DRG region could produce ‘unlocking’ of the respiratory rhythm from that of the respiratory pump. At other sites in this region, focal cooling could selectively block the effects of the inspiration‐facilitating reflex induced by deflation without blocking the inspiration‐inhibiting Hering‐Breuer reflex. Unilateral focal cold blocks in the region of the intermediate part of the ventral respiratory group of neurons, VRG, generally caused depression of the rate of rise of inspiratory activity, but almost never apneustic effects. All effects of unilateral focal cooling both in the DRG and VRG were bilaterally symmetrical. No systematic differences between the effects on phrenic and external intercostal inspiratory activity were found in response to focal cooling either of the DRG or VRG suggesting that differential control of phrenic and external intercostal motoneurons is not exerted mainly at the level of these medullary structures. The results suggest that the DRG and VRG areas exert somewhat different effects on the respiratory pattern: DRG appears to be more concerned with integration of vagal and other inputs contributing to the inspiratory off‐switch mechanisms which, however, are not confined only to the DRG. The VRG inspiratory mechanisms, on the other hand, appear to be more involved in the gain control of the inspiratory out

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07667.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Unilateral focal cold blocks (20°C) in structures located ventrolaterally in rostral medulla consistently caused apnoea or deep depression of inspiratory motor output. The inhibitory effect could be correlated with the cooling temperature. Apnoeic response occurred either with complete absence of any inspiratory activity or combined with low level tonic inspiratory motor activity (‘tonic apnoea’). The appearance of apnoea was CO2‐independent, whereas the tonic component of the latter increased with increasing levels ofPCO2. The results suggest that the structures in the deep, ventro‐lateral aspect of rostral medulla, from which apnoea can be induced, correspond partly to the nucleus paragigantocellularis lateralis (nPGL) and the nucleus preolivaris. These structures appear to be relevant for the drive inputs necessary for respiratory rhythmogenesis. Unilateral focal cooling in the rostral medulla, including the ‘Bötzinger Complex’, caused increments in respiratory rate both in vagotomized and non‐vagotomized animals. The increase in respiratory rate in response to cooling in the region of the ‘Bötzinger Complex’ was combined with either an enhancement or some depression of respiratory motor output. This area in the rostral part of the ventral respiratory group (VRG) seems not to be crucial for respiratory rhythmogenesis, but to play a role in determining both the intensity and timing of the respiratory activity. All effects of unilateral cold block were bil

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07668.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Disinhibition or ‘release’ of expiratory muscle activity in response to focal cooling of various medullary structures was of two kinds: (1) release of rhythmic expiratory activity even when no such activity was recruited in the control situation and (2) release of tonic activity in the ‘expiratory’ muscles. Release of rhythmic expiratory activity was mainly elicited by focal cooling of structures in the intermediate part of the medulla and release of tonic activity was preferentially induced by cooling rostroventral structures, although a considerable overlap did occur. Release of rhythmic expiratory activity was not related to any changes in expiratory time (TE) or to any associated variations in the pattern of inspiratory activity. It showed a marked increase with increasing levels ofPCO2. The release of tonic activity was not CO2‐dependent. Both types of effects could be mimicked by focal microinjections of lignocaine and were reflected by corresponding changes in activity of a majority of the expiration‐related neurons. These results suggest that complex and widespread neural substrates subserve the control of the intensity of rhythmic expiratory activity and of the tonic activity of the abdominal and intercostal muscles. These neural mechanisms can apparently operate independently from those controlling the inspiratory activity. The release of the tonic activity observed in the ‘expiratory’ muscles might reflect a disinhibition of mechanisms involved in non‐respiratory functions of e

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07669.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The elemental distribution in acinar cells of rat pancreas was investigated by X‐ray microanalysis of thin, freeze‐dried cryosections. In the resting cell, the highest calcium concentrations were found in the basal part of the cell (including the endoplasmic reticulum) and in the zymogen granules. Mitochondrial calcium concentrations were low. Zymogen granules were rich in sulphur, but low in phosphorus, sodium and potassium. Stimulation of the pancreas by perfusionin vivowith the cholinergic agonist carbachol caused a significant decrease of the calcium concentration in the basal part of the cell and an increase in the calcium concentration in the apical part of the cell. The mitochondrial calcium concentration was not significantly altered. In addition, increased sodium and decreased potassium concentrations, giving rise to a significant increase in Na/K ratio were observed in all cell compartments measured, except in the zymogen granu

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07670.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The effects of neuropeptide Y (NPY) on contractility of the spontaneously beating guinea‐pig atrium and transmural nerve stimulation (TNS)‐induced efflux of tritium‐noradrenaline (3H‐NA) were studiedin vitro.NPY induced a moderate positive chronotropic and inotropic atrial response, which was resistant to metoprolol. TNS at 2 Hz for 2 s caused an increase in rate and contractile force. These effects were significantly reduced by NPY. NPY also reduced the TNS induced (2 Hz for 20 s), fractional [3H]NA release by 40% without affecting the contractile response. The contractile effects of exogenous NA on the guinea‐pig atrium were not affected by NPY. NPY caused a long‐lasting increase in coronary perfusion pressure, and also, in high doses, an inhibition of ventricular contractility in the isolated, perfused guinea‐pig heart. The perfusion pressure increase to NPY, which most likely reflects coronary vasoconstriction, was resistant to α and β‐adrenoceptor blockade but sensitive to the calcium antagonist nifedipine. A 50% reduction of the vascular NPY response occurred at 10‐9m nifedipine, which did not influence cardiac contractilityper seor the contractile effects of NA. NPY did not modify the increase in ventricular contractility induced by NA. Noradrenaline did not influence coronary perfusion pressure after β‐blockade. Since NPY is present together with NA in cardiac nerves, it may be suggested that NPY is involved in the regulation of NA release as well as the sympathetic control of atrial contractility a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07671.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Small intramyometrial arteries and pieces of adjacent myometrial tissue were obtained from 25 non‐pregnant women undergoing hysterectomy. Vascular and myometrial preparations were dissected, mounted in organ baths and isometric tension was recorded. Myometrial strips, but no vascular preparation, developed spontaneous contractile activity. Noradrenaline (NA) and vasopressin (VP) contracted both vessels and myometrium. Prostaglandin F2α(PGF2α) contracted the myometrial tissue, but had only a minor effect on the vessels. Removal of extracellular calcium almost abolished the myometrial responses to high K+(124 mm)‐solution, PGF2α, NA and VP. The vascular responses remaining after this treatment were 18% (K+), 34% (NA) and 25% (VP) of control contractions induced by high K+(124 mm). Nifedipine potently depressed myometrial contractions induced by NA and VP, but was less active against the vascular responses to these agents. In preparations exposed to calcium‐free medium, nifedipine (10‐7m) almost abolished myometrial contractions induced by calcium in the presence of K+(124 mm), NA or VP. It also effectively depressed vascular responses to calcium in the presence of K+, but was less active if NA and VP were present. It is suggested that PGF2αhas almost no contractant effect on intramyometrial arteries, and that the activation process in these vessels is much less dependent on extracellular calcium than that of the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07672.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Exposure to the β2‐adrenoceptor agonist terbutaline resulted in a transient stimulation of45Ca2+efflux from45Ca2+preloaded rat islets perfused in 2 mm Ca2+and 8.3 mm glucose. Concomitantly, an increase in insulin secretion occurred. Under the same experimental conditions, the α‐adrenoceptor agonist noradrenaline promptly inhibited insulin release without any apparent influence on45Ca2+efflux. In contrast, in a medium containing 2 mm Ca2+and a low glucose concentration (2.8 mm), terbutaline stimulated insulin secretion without any apparent effects on45Ca2+efflux. Noradrenaline had no effect on insulin secretion or45Ca2+efflux in this medium. When islets were perfused with 8.3 mm glucose in a Ca2+deficient medium, with or without addition of the chelating agent EGTA, terbutaline induced a marginal stimulation of insulin secretion and a negligible stimulation of45Ca2+efflux. On the contrary, noradrenaline stimulated to an immediate and notable45Ca2+efflux in these Ca2+deficient media. Noradrenaline also clearly inhibited insulin secretion, though less markedly and with a slower onset than in islets perfused in 2 mm Ca2+. When the islets were perfused in a Ca2+deficient medium with 2.8 mm glucose, terbutaline had a slight insulin releasing effect, but stimulated45Ca2+efflux potently. Noradrenaline had no influence on insulin secretion but a weak stimulatory effect on45Ca2+efflux. The data suggest that the β2‐adrenoceptor agonist terbutaline has the ability to stimulate insulin secretion in perfused rat islets, requiring extracellular Ca2+for the full expression of its effects. These effects may be exerted through a Ca2+‐Ca2+exchange over the cell membrane and/or through cAMP and intracellular Ca2+perturbations. Moreover, terbutaline directly stimulates45Ca2+efflux, an effect inhibited by glucose. Further, the α‐adrenoceptor agonist noradrenaline can inhibit insulin secretion in the absence of extracellular Ca2+, but the full expression of its inhibitory action is dependent on extracellular Ca2+and glucose. In addition, noradrenaline stimulates45Ca2+efflux in a Ca2+deficient medium, an effect which appears independent of the glucose

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07673.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

The objective of the present study was to investigate whether oxytocin is released in response to feeding in analogy to the response induced by suckling. Therefore, repeated plasma samples were drawn from dogs and pigs during feeding and suckling and oxytocin levels were determined by radioimmunoassay. As expected suckling gave rise to immediate and short‐lasting increases of oxytocin levels in both species. More surprisingly, feeding in female and male dogs as well as in lactating sows was accompanied by a similar‐sized rise of oxytocin levels. The oxytocin peak sometimes occurred before the actual period of suckling or feeding, suggesting that the output of oxytocin had been conditioned to visual, olfactory or auditory stimuli associated with both types of situations. It is well known that oxytocin is released in lactating animals in response to touching of the teats. It is possible that also the presence of food in the gastro‐intestinal tract activates neurogenic mechanisms which stimulates the release of oxytocin. Since oxytocin causes a release of insulin and VIP (vasoactive intestinal polypeptide), peptides which appear in the circulation following both suckling and feeding, it is suggested that oxytocin may be involved in the control of the suckling‐ and feeding‐related output of these

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07674.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

In man gymnemic acid is able to abolish the sweet taste. Also in man, the neural correlate of that effect is a disappearance of the response to sweet stimuli in the taste nerves, as indicated by the observations of Diamantet al.(1965). Although a variety of other mammals also show neural responses to sweet‐tasting compounds, the corresponding effect of gymnemic acid has not been demonstrated. This study presents chorda tympani proper nerve recordings from the chimpanzee before and after gymnemic acid. On the chimpanzee tongue, application of 2 ml gymnemic acid (3–10 mg·ml‐1for 3–4 min) completely abolished the taste responses to 0.0035 M acesulfam‐K, 0.0018 M aspartame, 0.015 M D‐tryptophan, 0.02% monellin, and 0.02% thaumatin, reduced by 75% the response to 0.3 M sucrose, and by 50% that of 0.76 M xylitol. No decrease was recorded in the responses to 0.001 M quinine, 0.1 M NaCl, 0.02 and 0.04 M ascorbic acid, 0.02 and 0.04 M citric acid. The response to the sweeteners recovered with time and the recovery was complete or nearly complete after one and a half hours. It was also found that after application of 2 ml miraculin, 3 mg·ml‐1for 3 min to the tongue the neural response to acids was about 1.5 times as large as before. Gymnemic acid applied before miraculin prevented this enhancement and gymnemic acid after miraculin depressed the enhancement by miraculin of the response to citric an

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07675.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY

摘要:

Human mixed saliva extracted with chloroform was found to contain immunoreactive melatonin which eluted in HPLC as synthetic melatonin. There was a clear diurnal rhythm in saliva melatonin with low day and high night levels. A similar rhythm was observed in serum. The high night levels in saliva were lower than the corresponding levels in serum. The calculated secretion rate of melatonin into saliva was<0.5‐0.9 pmol·h‐1during the day and 1.0–2.4 pmol·‐1during the night. Saliva sampling can be used as a simple and non‐invasive way of studying melatonin secretion in

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1985.tb07676.x

出版商:Blackwell Publishing Ltd    

年代:1985

数据来源: WILEY