摘要:

Anin vivomodel is described in which pentobarbital anaesthetized pigs were used to study the sympathetic nervous control of the nasal mucosal vascular bed. Changes in blood flow in the sphenopalatine artery (representing nasal blood flow) and in the volume of the nasal cavity (mainly reflecting blood content in venous sinusoids), upon electrical stimulation of the cervical sympathetic trunk, were recorded simultaneously. Single impulses (15V, 5 ms) reduced both the arterial flow and the volume of the nasal mucosa. The effects of nerve stimulation with a continuous train of impulses at 0.59, 2 and 6.9 Hz were compared with those caused by stimulation with the irregular bursting pattern, triggered by recorded human sympathetic vasoconstrictor nerve activity, with the same average frequencies. Both types of stimulation reduced nasal blood flow and volume, but the responses were significantly larger with burst stimulation at 0.59 Hz. The volume reduction was already maximal at 0.59 Hz while the blood flow response increased further higher frequencies. Local intra‐arterial pretreatment with the α‐adrenoceptor antagonist phenoxybenzamine significantly attenuated the flow and volume responses to single impulses, while clear‐cut reductions in blood flow (by 40%) and volume (by 80%) remained, upon stimulation, at 6.9 Hz. Noradrenaline given intra‐arterially caused a dose‐dependent reduction in nasal blood flow and volume. The noradrenaline effects were blocked by phenoxybenzamine treatment.The results show that the pig nasal mucosa represents a model where both blood flow and volume changes can be studied in parallelin vivo.Furthermore, stimulation with the firing pattern of human vasoconstrictor nerves, i.e. irregular bursts, causes larger vascular responses in the pig nasal mucosa compared to a continuous stimulation. The large residual vascular responses to sympathetic nerve stimulation at high frequency after a‐adrenoceptor blockage may be mediated by some other non‐adrenergic transmitte

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08301.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Vasomotor effects of the amines, serotonin (5‐hydroxytryptamine; 5‐HT), noradrenaline (NA) and histamine, were studied in isolated basilar arteries (BA) of the rat and guinea‐pigin vitro.5‐HT produced marked contraction in rat BA, about 70% of that induced by high (124 mM) K+solution. This response was inhibited by the specific 5‐HT2receptor antagonist, ketanserin, with a pA2value of 9.35. In the guinea‐pig, 5‐HT caused only moderate contraction amounting to 30% of that produced by K+. Ketanserin at concentrations up to 10‐6M showed a comparatively small, non‐surmountable inhibition of the contraction.EC50values for 5‐HT in the guinea‐pig and rat were 5.65 times 10‐8m and 3.70 times 10‐7M, respectively. NA had no effect on rat BA, but moderately contracted guinea‐pig BA. The contraction was not altered by yohimbine but was inhibited by prazosin. Histamine contracted guinea‐pig BA with a maximum that was 110% of the K+‐induced contraction. It was not changed by the H2antagonist, cimetidine. The H1antagonist, pyrilamine, caused competitive inhibition with a pA2of 9.20 at a slope of 0.94. In preconstricted rat BA, histamine induced vasodilatation in a concentration‐dependent manner. The Hj agonist, pyridylethylamine (PEA), and the H2agonist, impromidine, dilated less effectively than histamine. The vasodilatation induced by histamine was inhibited by the H2antagonist, cimetidine, and to a smaller extent by the H1‐receptor antagonist, pyrilamine. Removal of the endothelium abolished the vasodilator effect of PEA but not that of impromidine. In vessels with intact endothelium, the vasodilatation caused by histamine was slightly reversed by pyrilamine, which did not affect the dilatation in endothelium denuded vessels. Cimetidine markedly reversed this vasodilator effect in both intact and endothelium denuded preparations; in the latter the counteraction was almost complete. In precontracted guinea‐pig vessels, histamine failed to induce dilatation even in the presence of the H1antagonist, pyrilamine. Thus, 5‐HT‐induced contraction is mediated by 5‐HT2receptors in the rat and probably by 5‐HT1receptors in the guinea pig. NA failed to contract rat BA but contracted guinea‐pig BA through α1receptors. Histamine was a potent dilator agent in rat BA through a combination of both H1and H2receptors. The dilatation mediated by the H1receptors, but not that mediated by H2receptors, was endothelium‐dependent. Histamine caused strong vasocon

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08302.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

摘要:

Intracellularly recorded voltage responses of the visual cells of the blowfly (Calliphora erythrocephala) were analysed in the time and frequency domains. The photoreceptors were stimulated with pulse (impulse), sine, sine‐sweep and pseudorandomly (white noise) modulated green light. The blowfly photoreceptor responses, as analysed from the linear transfer functions, seem to arise from a system similar to that of cascaded low‐pass Alters, with a corner frequency at about 63 Hz (SD ± 12 Hz). The system is likely to have at least five poles, including one linear second order term, and a pure delay element. Arising from the non‐linearities a second harmonic can be seen in the power spectra of responses elicited by sine modulated light. This non‐linearity is at least partly explained by the self‐shunting property of the membrane voltage response. Light adaptation increases the non‐linearities in frequencies lower than 20 Hz, as seen in the decrease of the coherence function with the signal‐to‐noise ratio remaining constant. Light adaptation also accelerates the transduction process and it appears in the linear transfer function in a form typical to negative feedback. With low stimulus frequencies it causes a ‘phase lead’‐type non‐linearity. In addition, the sine‐sweep responses show quite different frequency characteristics in respect of depolarization and repolarization. Lateral inhibition between photoreceptor responses recorded from retinular cell axons in the lamina appears as a drop in gain and as an increasing phase‐lag in frequencies from 30 Hz upwards in linear transfer functions. The source of this capacitive‐like coupling can be considered to be in the high resistance barriers compartmentalizing the second optic ganglion

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08303.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08304.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08305.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08306.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08307.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1988.tb08308.x

出版商:Blackwell Publishing Ltd    

年代:1988

数据来源: WILEY