[Effect of intraventricular injection of substance P on pulmonary and carotid arterial pressure in rabbits]

In the present investigation changes of pulmonary and carotid arterial pressure in response to injection of substance P(SP) into the 4th ventricle of rabbits were studied. The results were as follows: (1) Intraventricular (ivt.) injection of SP could induce either an increase or a decrease in pulmonary arterial pressure as well as carotid arterial pressor response and bradycardia. (2) Bilateral cervical vagotomy could initiate a definite pulmonary pressor response and a marked decrease in the bradycardiac response to injection of SP in those rabbits originally showing a depressor response of pulmonary artery to SP. (3) Pretreatment by i.c.v. and i.v. phentolamine or alpha 1 blocker, prazosin, could block both the SP-induced pulmonary and carotid pressor responses. (4) alpha 2 blocker, yohimbine, or naloxone could enhance the pressor responses in the both arteries. (5) Propranolol had no effect on the pressor responses in both arteries. (6) The cardiovascular responses to SP could be blocked by the SP blocker (D-Pro2.D-Trp7.9)-SP. It is assumed that increase of SP in the brain may induce an increase in both the pulmonary and carotid arterial pressures and bradycardia by activating the SP receptors. The central mechanism responsible for the SP- induced pressor response involves the participation of adrenergic alpha 1 receptor activities, while the central adrenergic alpha 2 receptor system as well as the endorphin system exerts an inhibitory modulation on the central SP-induced pressor pathway. It appears that SP, catecholamine and opiate substance are all involved in the regulation of blood pressure by brain stem.

Vasomotor responses in the isolated perfused external and internal carotid vascular beds of the rat

1. The external (ECB) or the internal (ICB) carotid vascular beds of the rat were isolated and perfused with Krebs-Henseleit solution at constant flow (1 ml/min). Changes in perfusion pressure (PP) were recorded after cervical sympathetic stimulation and after the administration of norepinephrine (NE) and serotonin (5-HT). 2. Sympathetic stimulation induced an increase in PP (vasoconstriction) in both vascular beds, however, this effect was significantly higher in the ECB than in the ICB. 3. Exogenous NE also induced a significantly higher contractile response in the ECB. 4. Prazosin (10(-8) M) significantly inhibited the response to sympathetic stimulation and to NE both in the ECB and in the ICB, but yohimbine (10(-7) M) had no effect, suggesting that the vasoconstriction was mainly due to the activation of alpha 1-adrenoceptors. 5. 5-HT induced a contractile response both in the ECB and the ICB. In contrast with the response to NE, the contraction induced by 5-HT in the ICB was significantly higher than in the ECB. 6. Ketanserine (10(-8) M) antagonised both responses, indicating the involvement of 5-HT2 receptors. 7. The contractile effect of 5-HT in the ECB was significantly enhanced by a subthreshold sympathetic stimulation that did not modify the PP by itself. This effect was not seen in the ICB. 8. The differential perfusions of the ECB or the ICB demonstrated a different reactivity of ECB and ICB, both to sympathetic stimulation and to the administration of exogenous NE or 5-HT. 9. Furthermore, the response to 5-HT in the ECB was modulated by a subthreshold sympathetic stimulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Severe facial ischaemia caused by ergotism

A case of ergotamine induced severe face ischaemia mimicking acute arteritis is presented. The unique clinical picture was due to bilateral involvement of both external carotid arteries. No case of ergotism with such a localization has been previously described in the literature.

Response of canine internal carotid system to acetylcholine

The reactivity of the canine internal carotid system to acetylcholine (10(-8)-10(-4) M) was studied isometrically with 4-mm cylindrical segments from cervical and cavernous portions of the internal carotid artery and from the middle cerebral artery. Under control conditions, the cervical portion relaxed to every dose, the cavernous portion relaxed at low concentrations (10(-8)-10(-6) M) and contracted at higher concentrations (10(-5)-10(-4) M), whereas the middle cerebral artery contracted to every dose of acetylcholine. These responses were blocked by atropine (10(-6) M). Without endothelium, the cervical portion exhibited a lower relaxation, the cavernous portion contracted, and the middle cerebral artery was practically unresponsive to acetylcholine. These responses were also blocked by atropine. It suggests that the reactivity of the internal carotid system to acetylcholine 1) is endothelium dependent and 2) changes as it courses toward the brain, and this could be related to different embryological origin of the components of this arterial system.

Reproducibility of Doppler blood flow velocity waveform measurements: study on variability within and between day and during haemodynamic intervention in normal subjects

Reproducibility of Doppler blood velocity waveform measurements in external and internal carotid, middle cerebral, and brachial arteries and ascending aorta was determined in 8 normal male volunteers twice daily on three occasions each separated by two or more weeks. Measurements were made in supine and standing positions at rest and after taking glyceryl trinitrate and in the supine position after performing a standardized exercise test. The Doppler blood flow waveform indices showed a between days coefficient of variation of less than 15% both for baseline measurements and during haemodynamic change induced by exercise or glyceryl trinitrate. We conclude that Doppler blood velocity waveform measurement in different vascular beds is reproducible at baseline and when the cardiovascular system is interrupted pharmacologically or physiologically.

A possible role of the glomus cell in controlling vascular tone of the carotid labyrinth of Xenopus laevis

To clarify the physiological significance of the g-s connection (intimate apposition of the glomus cell to the smooth muscle) in the Xenopus carotid labyrinth, experiments were carried out morphologically and physiologically. Results obtained are as follows. Efferent electrical stimulation of the glossopharyngeal nerve resulted in concentrating dense-cored vesicles on the peripheral region of the glomus cell, and a decrease of vesicles as a whole. In the carotid labyrinth perfused artificially, outflow of the internal and the external carotid arteries decreased with administration of catecholamines (adrenaline, noradrenaline and dopamine). Acetylcholine reduced only the internal outflow. This response was depressed by atropine, hexamethonium and phentolamine, whereas accelerated by propranolol. Sodium cyanide reduced the internal outflow without affecting the external outflow, and its effect is depressed by phentolamine. From these results, a possibility that the glomus cell participates in controlling the blood flow in the labyrinth through the intervention of the g-s connection was discussed.

Neurogenic muscarinic vasodilation in the cat. An example of endothelial cell-independent cholinergic relaxation

Nerve-mediated and acetylcholine-induced dilator behavior of feline posterior auricular arteries was studied in vitro. We evaluated the muscarinic nature and endothelial cell-dependence of the vasodilations and attempted to determine if there are inhibitory muscarinic receptors located directly on the smooth muscle cells in this artery. Transmural nerve stimulation of arteries which were pretreated with guanethidine (5 X 10(-6)M) and constricted with prostaglandin F2 alpha (3 X 10(-6)M) caused a frequency-dependent, tetrodotoxin-sensitive relaxation of up to 50% of induced tone. Atropine (10(-7)M) blocked more than 95% of this response at all frequencies. Removal of the endothelium by rubbing the intimal surface did not affect the magnitude of the response, but prolonged it slightly. Neurogenic relaxations in rubbed preparations were atropine-sensitive, although less so than control at higher stimulation frequencies. Relaxation of this artery to the calcium ionophore A23187 was completely endothelial cell-dependent. However, exogenous acetylcholine caused dose-dependent relaxations both in control and rubbed preparations. We conclude that the posterior auricular artery is an example of a blood vessel which has muscarinic receptors located directly on its smooth muscle cells which, when activated by acetylcholine released from perivascular nerves, mediate a smooth muscle cell relaxation. This finding contrasts with models of the vascular smooth muscle cell which indicates an excitatory role for muscarinic receptors.

Influence of chronic stellectomy on reactivity to serotonin in the dog external carotid bed

The influence of chronic stellectomy on external carotid flow responses to i.a. serotonin (5HT) was determined in dogs in which both stellate ganglia had been removed 1, 2, 4 or 8 weeks previously. The effect of this maneuver on carotid and heart rate responses to i.a. and i.v. norepinephrine (NE), respectively, was also assessed for comparison. Constrictor responses to NE in the carotid were moderately increased at 2 and 4 weeks, while its positive chronotropic effects were markedly augmented throughout the observation period. Dilator responses to 5HT increased at 4 and specially at 8 weeks after stellectomy. Results obtained with NE were considered compatible with supersensitivity induced by decentralization in the carotid and by denervation in the heart. Changes in carotid responses to 5HT were interpreted as being due to a prejunctional mechanism similar to that responsible for supersensitivity to NE. Differences in the time course of development of supersensitivity to both amines were attributed to masking of 5HT dilatation by NE released by the indoleamine at the time of increased sensitivity to constriction by the catecholamine.

Redistribution of flow between canine isolated internal and external carotid arteries by vasoactive substances

A Y-shaped segment consisting of the common, internal, and external carotid arteries was isolated from the canine carotid artery. The preparation has the advantage of allowing direct comparison of responses to vasoactive substances in the internal and external carotid arteries. It was perfused at a constant rate (within the range of 10-15 ml/min) through the common carotid with either Locke's solution or arterial blood led from a support dog. Adding norepinephrine or epinephrine to the perfusate raised the perfusion pressure, increased the flow along the internal carotid branch, and decreased it in the external carotid branch in the blood-perfused experiments but not in the saline-perfused ones. In contrast, 5-hydroxytryptamine, prostaglandin F2 alpha, and ATP caused a decrease in internal carotid flow and an increase in external carotid flow, raising the perfusion pressure in both experiments. Controlled bleeding of the support dog (at the rate of 4 ml/(kg X min] produced a similar result to that produced by exogenous norepinephrine or epinephrine. These findings may suggest that a redistribution of blood flow between the larger internal and external carotid arteries can be induced by a difference of responsiveness to certain vasoactive substances between the two arteries.

[Doppler ultrasound studies of the extracranial cerebral vessels in migraine patients after ergotamine tartrate administration]

Doppler ultrasound investigations were done in 20 patients with migraine during the symptom-free interval after oral administration of 2 mg and 6 mg ergotamine tartrate. The observed changes of end-diastolic flow velocity as a measure of peripheral total resistance permit simultaneous assessment of the vasoconstrictor effect of ergotamine in the perfusion area of the internal and external carotid arteries. A dosage of 2 mg led to an exclusive increase of resistance in the external carotid artery area without significant changes in the internal carotid area. A maximal therapeutic dosage of 6 mg ergotamine tartrate did not lead to a significant increase of the vasoconstrictor effect in the external carotid circulation. In addition, a barely registrable increase of resistance in the internal carotid area could now be observed.

The feline carotid rete: vasomotor reactivity of isolated arteries

Vasomotor responses of arteries from the feline carotid rete were examined using a sensitive in vitro system. The vessel segments constricted in response to several vasoactive agents and putative neurotransmitters. Sympathomimetic agents (noradrenaline, adrenaline, oxymetazoline, phenylephrine), 5-hydroxytryptamine, histamine, angiotensin II, and prostaglandin F2 alpha all induced concentration-dependent contractile responses. The contractions induced by noradrenaline, 5-hydroxytryptamine, and histamine could be antagonized by phentolamine, methysergide, and mepyramine, respectively. Cholinomimetics (acetylcholine, carbacholine), vasoactive intestinal peptide and papaverine induced potent dilatory responses. The effect of carbacholine was shifted towards higher agonist concentrations by atropine. Dilatations, though small in magnitude, were found by application of adenosine, isoproterenol, and histamine. These results correlate well with the recent demonstration of autonomic nerves and indicate the occurrence of corresponding receptor sites in the walls of the carotid rete arteries.

[Comparative responsiveness of isolated saphenous, femoral and external carotid arteries and veins of dogs to dihydroergotamine mesylate (DEM) (author's transl)]

Changes in tension of spiral strips of saphenous, femoral and external carotid arteries and veins were measured isometrically. DEM stimulated 6 preparations in almost the same concentration ranges (pD2 values were 8.64 to 8.40). However, the dose-response curves for DEM indicted variations in responsiveness among the different arteries and veins. Compared with norepinephrine (NE) (1)( the intrinsic activity of DEM was 0.002 on saphenous arteries, 0.05 on saphenous veins, 0.03 on femoral arteries, 0.18 on femoral veins, 0.13 on external carotid arteries and 0.13 on external carotid jugular veins. Thus DEM contracted more potently the venous strips from the hind limbs. IN femoral and external carotid arteries, antagonism of serotonin by DEM or methysergide was investigated. DEM displaced the dose-contractile response curves for serotonin in a noncompetitive manner, and the antagonistic response of DEM to serotonin was about 8 times more effective in external carotid arteries (pD'2 value=6.96) than in femoral arteries (pD'2 value=6.05). Methysergide, unlike DEM, antagonized the response to serotonin in a competitive manner at low doses but in a noncompetitive manner in high doses, and was fairly equal in antagonizing response to serotonin in external carotid arteries (pA2 value=that the therapeutic value of DEM in the treatment of orthostatic hypotension is due to its selective anti-serotonin activity on the external carotid arteries.

Isolated, blood-perfused canine arteries: different vasoconstrictor responses of internal and external carotid arteries to 5-hydroxytryptamine

Canine carotid arteries were isolated, suspended in a bath and perfused under a constant flow rate with arterial blood led from a support dog. Resting perfusion pressure was set at a constant level over 50 mm Hg. Drugs were administered into the endothelial side of the artery through a cannulated tubing and the response was obtained as pressure changes. This preparation was proved to be superior to usual isolated arterial strips, since its reactivity was kept in a stable condition over 5-10 hours at 37 degrees C. Using this preparation, effects of 5-hydroxytryptamine (5-HT) on the internal and external carotid arteries were investigated in comparison with effects of norepinephrine. In the internal carotid artery, 5-HT caused a much more potent vasoconstriction than norepinephrine. On the other hand, in the external carotid artery, 5-HT caused only slight vasoconstriction, while norepinephrine produced a marked vasoconstriction.

Internal and external carotid vascular responses to vasoactive agents in the monkey

Internal and external carotid blood flows in anesthetized monkeys were measured simultaneously using electromagnetic flowmeters. Complete dose-response relationships were established for the effects of intracarotid infusion of several humoral agents implicated in migraine. Both the internal and external carotid vasculatures were constricted by serotonin and prostaglandin F2alpha and dilated by bradykinin, histamine, and acetylcholine. Noradrenalin and adrenaline constricted the external carotid vasculature but had little direct effect in the internal carotid territory. Prostaglandin E1 dilated the external carotid vasculature. Low doses of prostaglandin E1 produced dilation in the internal carotid circulation, but with higher doses there was a paradoxical abolition of this effect.

Actions of bradykinin on isolated cerebral and peripheral arteries

The addition of bradykinin (BK) caused a dose-related contraction in helical strips of canine cerebral, internal carotid, external carotid, and femoral arteries, while the peptide elicited a relaxation in canine coronary, renal, and mesenteric arteries contracted with 5+ or prostaglandin F2alpha. In contrast to canine cerebral arteries, human cerebral arteries contracted with K+ or prostaglandin relaxed with BK. Contractile responses of canine cerebral arteries to BK were not influenced by phentolamine, diphenhydramine, and methysergide, but were attenuated by aspirin and indomethacin. Contractions induced by K+ were not or only slightly inhibited by these anti-inflammatory agents. Polyphloretin phosphate failed to reduce BK-induced contractions. Relaxing effects of BK on canine coronary arterial strips were not altered by atropine, propranolol, metiamide, and aminophylline, but were inhibited by aspirin and indomethacin. Adenosine-induced relaxation was unaffected by the latter two agents. It may be concluded that adrenergic, cholinergic, histaminergic, and adenosine-related mechanisms are not involved in the genesis of BK-induced contraction and relaxation. Contractile responses of canine cerebral arteries to BK do not appear to derive from prostaglandins released, but rather from a direct action on vascular smooth muscle cells.

Cerebral arterial spasm. Part 7: In vitro effects of alpha adrenergic agents on canine arteries from six anatomical sites and six blocking agents on serotonin-induced contractions of the canine basilar artery

In vitro experiments were performed using a small volume chamber to determine the contractile activity of several adrenergic agents on arteries from six locations of the canine vascular bed. Cumulative log-dose response curves were obtained for epinephrine, norepinephrine, phenylephrine and dopamine. It was found that the basilar and internal carotid arteries responded much less to these agents than did the mesenteric, renal and femoral arteries. Six blocking agents including nitroprusside were tested to determine their effect on the response of the canine basilar artery to log-dose additions of serotonin, prostaglandin F2alpha and KC1. Another chamber was developed to study the differential effect of nitroprusside and papaverine when placed on the luminal side versus the adventitial (cerebrospinal fluid) side of the basilar artery during a sustained contraction with serotonin. A theoretical treatment of cerebral arterial spasm following a subarachnoid hemorrhage is presented.

Effect of vasodilating drugs on external carotid and pulpal blood flow in dogs: "stealing" of dental perfusion pressure

Blood flow in the external cartoid artery (ECBF) and dental pulp (PBF) was measured during arterial infusion of vasodilators (isoprenaline, papaverine, acetylcholine and bradykinin). Systemic arterial pressure (AP) and local arterial pressure of the teeth (LAP) were recorded in a femoral and the lateral nasal artery respectively. All four vasodilators were found to increase ECBF and simultaneously reduce lateral nasal arterial pressure--or in other words-to STEAL" PERFUSION PRESSURE FROM THE TEETH. AP remained practically unchanged whereas PBF was variably affected. During infusion of isoprenaline PBF decreased on average by 19% of control. Papaverine nearly doubled PBG, while bradykinin caused no consistent change. Great pulpal flow variations were often recorded during constant acetylcholine infusion rate. The variable effect of the four vasodilators on PBF could partly be explained by the fall in LAP. Calculated pulpal resistance (LAP/PBF) showed no consistent change during isoprenaline infusion, bradykinin caused a slight fall and papaverine reduced LAP/PBF by 49%. The experiments demonstrate that due to the "stealing" of dental perfusion pressure caused by vasodilation in the neighbouring tissues, the effect of vasodilators on pulpal resistance vessels cannot be estimated without knowledge of the pressure in the small arteries directly feeding the teeth.

Comparative effects of four migraine prophylactic drugs on an isolated extracranial artery

Clonidine and methysergide constrict the rabbit auricular artery by activating smooth muscle alpha-adrenoceptors. Clonidine inhibits and methysergide enhances responses to stimulation of the sympathetic nerves. Both drugs sensitise the artery to a variety of vasoconstrictor stimuli, although not to potassium chloride. This weak generalised sensitisation may depend on clonidine and methysergide themselves being vasoconstrictor since sensitisation after clonidine did not occur when vasoconstriction was abolished with phentolamine. The marked potentiation of 5-HT and tryptamine observed during clonidine perfusion may reflect a property of the tryptamines since it was observed during perfusion with histamine but not when histamine vasoconstriction was abolished with mepyramine. Cyproheptadine and pizotifen neither constrict the artery nor sensitise it to vasoconstrictor agents. They inhibit responses to nerve stimulation, alpha-adrenoceptor agonists, potassium chloride and particularly histamine. Sensitisation of blood vessels reinforced by direct vasoconstriction may contribute to the mechanism of action of clonidine and methysergide in migraine. Conversely, alterations in vascular function may be less important to the antimigraine actions of either cyproheptadine or pizotifen.

Responsiveness of isolated canine cerebral and peripheral arteries to ergotamine

Changes in tension of spiral strips from dog saphenous, external carotid and basilar arteries were monitored isometrically. Serotonin (5-HT) contracted the 3 arterial preparations in about the same concentration range. Compared with noradrenaline (NA) (100%) the efficacy of 5-HT was about 60% on saphenous, 150% on external carotid and about 500% on basilar arteries. Ergotamine (E) stimulated the 3 vascular preparations in concentrations about 100 times lower than 5-HT. Compared with NA the efficacy of E was about 20% on saphenous, 50% on external carotid and 200% on basilar arteries. Compared with 5-HT (100%) however, E had similar constrictor activities in the 3 arteries. It seemed likely therefore that 5-HT receptors are involved in the vasoconstrictor activity of E. Evidence for this was obtained in experiments in which cyproheptadine (Cy), a 5-HT antagonist, was used. For antagonism of E concentrations of Cy about 6 times higher than those required to inhibit 5-HT were necessary, whereas for antagonism of NA about 500 times higher Cy concentrations were necessary. The results suggest that on canine arterial vascular smooth muscle the constrictor activity of E is mediated mainly through serotoninergic receptor sites.

Responsiveness of isolated cerebral and peripheral arteries to serotonin, norepinephrine, and transmural electrical stimulation

Spirally cut strips of cerebral and peripheral arteries from dogs were used for comparing the vasoconstricting effect of serotonin, norepinephrine, K + , and transmural electrical stimulation. Sensitivity of cerebral (basilar, posterior cerebral, and middle cerebral) arterial strips to serotonin was markedly greater than that to norepinephrine with respect to the median effective concentration (ED 50 ) and the maximum response. Contractile responses of isolated human cerebral arteries to serotonin and norepinephrine were similar to those observed in the dog arteries. In contrast, proximal and distal strips from superior mesenteric arteries and strips from renal arteries were more sensitive to norepinephrine than they were to serotonin. Mean values of contractions caused by 5 x 10 -6 M serotonin relative to those caused by 30 mM K + in cerebral, internal carotid, external carotid, common carotid, and superior mesenteric arteries were in a descending order, whereas those for norepinephrine were in an ascending order. These studies demonstrate that a gradual transition occurs from characteristic responses seen in mesenteric arteries (high sensitivity to norepinephrine, low sensitivity to serotonin) to those seen in cerebral arteries (high sensitivity to serotonin, low sensitivity to norepinephrine). Transmural stimulation did not produce contractions of cerebral and internal carotid arteries, but contractions were produced in external carotid, common carotid, and superior mesenteric arteries. It appears that sympathetic nerves cannot play an important role in the regulation of vascular tone in large cerebral arteries.