Restoration Algorithm-Based Ultrasound Image in Evaluating the Effect of Dexmedetomidine on Patients with Neurological Disorder Anesthetized by Sevoflurane

The study focused on the application value of ultrasound images processed by restoration algorithm in evaluating the effect of dexmedetomidine in preventing neurological disorder in patients undergoing sevoflurane anesthesia. 90 patients undergoing tonsillectomy anesthesia were randomly divided into normal saline group, propofol group, and dexmedetomidine group. The ultrasound images were processed by restoration algorithm, and during the postoperative recovery period, ultrasound images were used to evaluate. The results showed that the original ultrasonic image was fuzzy and contained interference noise, and that the image optimized by restoration algorithm was clear, without excess noise, and the image quality was significantly improved. In the dexmedetomidine group, the extubation time was 10.6 ± 2.3 minutes, the recovery time was 8.4 ± 2.2 minutes, the average pain score during the recovery period was 2.6 ± 0.7, and the average agitation score was 7.2 ± 2.4. Of 30 patients, there were 13 cases with vertigo and 1 case with nausea and vomiting. The vascular ultrasound imaging showed that, in the dexmedetomidine group, the peak systolic velocities (PSV) of the bilateral vertebral arteries during the recovery period were 67.7 ± 14.3 and 67.9 ± 15.2 cm/s, respectively; the end-diastolic velocities (EDV) of the bilateral vertebral arteries were 27.8 ± 6.7 and 24.69 ± 5.9 cm/s, respectively; the PSV in bilateral internal carotid artery systolic peak velocities were 67.2 ± 13.9 and 67.8 ± 12.7 cm/s, respectively; the EDV in bilateral internal carotid arteries were 27.7 ± 5.3 and 26.9 ± 4.9 cm/s, respectively; bilateral vertebral artery resistance indexes (RIs) were 0.6 ± 0.02 and 0.71 ± 0.08, respectively; the bilateral internal carotid artery RIs were 0.57 ± 0.04 and 0.58 ± 0.06, respectively, all better than the normal saline group (12.1 ± 2.5 minutes, 10.1 ± 2.3 minutes, 3.9 ± 0.6, 10.6 ± 3.7, 15 cases, 11 cases, 81.5 ± 13.6, 80.7 ± 11.6 cm/s, 29.3 ± 6.8, 28.9 ± 6.7 cm/s, 74.3 ± 10.2, 73.9 ± 12.5 cm/s, 29.1 ± 4.3, 29 ± 4.5 cm/s, 0.84 ± 0.06, 0.83 ± 0.05, 0.8 ± 0.04, and 0.81 ± 0.05) and the propofol group (11.4 ± 2.1 minutes, 9.0 ± 2.1 minutes, 3.4 ± 0.8, 8.5 ± 2.3, 12 cases, 9 cases, 72.5 ± 12.9, 73.4 ± 11.8 cm/s, 28.6 ± 5.4, 26.5 ± 5.1 cm/s, 72.1 ± 11.4, 73.5 ± 10.6 cm/s, 28.8 ± 5.6, 27.3 ± 4.7 cm/s, 0.78 ± 0.07, 0.82 ± 0.06, 0.76 ± 0.03, and 0.78 ± 0.05), and the differences were statistically significant (P < 0.05). In conclusion, ultrasound images processed by restoration algorithm have high image quality and high resolution. The dexmedetomidine can prevent neurological disorder in patients with sevoflurane anesthesia and is suggested in postoperative rehabilitation.

The therapeutic effect and mechanism of Chinese medicine Xuan-Yun-Ding on posterior circulation ischemia with vertigo in a rabbit model

The aim of research is to unveil the mechanisms of the beneficial effects of XYD on PCIV in a rabbit model. 40 New Zealand white rabbits were randomly divided into 5 groups,including normal control group (NC), model control group (MC), low-dose of XYD group (LXYD), high-dose of XYD group (HXYD) and Yang-Xue-Qin-Nao group (YXQN). PCIV rabbit model was established by feeding high-fat diet companied with paravertebral sclerotherapy and rotation exercise. The general observation, step-down test, rheoencephalogram, blood tests, histopathological detection and the plasma concentration of the effective component of XYD were investigated. After pharmacological intervening, the step-down time, REG, PL, IPL, blood viscosity, the levels of blood lipids, CRGP were significantly improved. Moreover, the vertebral artery showed the reduced stenosis of arterial lumen and less proliferation of fibrous tissue in the arterial wall in the LXYD, HXYD and YXQN group. Based on the LC-MS detection, the blood concentrations of puerarin in the LXYD and HXYD group were significantly increased after pharmacological intervening. XYD could ameliorate the symptoms of vertigo, Qi-deficiency and blood stasis in PCIV rabbits via effectively regulating the levels of blood lipids and vasoactive substances, decreasing blood viscosity, increasing CBF and protecting vestibular function.

[Effects of Huoxue Dingxuan Capsule Glare on Vertebral Artery Blood Flow,Plasma PAI and t-PA in CSA Rat Models.]

OBJECTIVES

To determine the effects of Huoxue Dingxuan Capsule on vertebral artery blood flow,plasma plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI) in rats with cervical spondylosis of vertebral artery type (CSA).

METHODS

Ninety healthy male Wistar rats were equally and randomly divided into control,model and treatment groups.The rats in the model and treatment groups were subject to composite modeling manufacturing CSA.The treatment group was given six-week interventions with Huoxue Dingxuan capsule 4 weeks after the modeling.Vertebral artery blood flow,plasma PAI,and t-PA contents were detected before modeling,prior to the interventions,and post interventions.

RESULTS

Before the interventions,the rats in the model and treatment groups had significantly lower blood flow of vertebral artery than the controls (P<0.05).The model rats also had increased serum PAI and t-PA contents (P<0.01).After the interventions,significantly higher vertebral blood flow was found in the treatment group compared with the controls (P<0.05).After the interventions,increased serum PAI and t-PA contents were observed in the rats in the model group (P<0.01);whereas,decreased serum PAI and t-PA contents were observed in the rats in the treatment group (P<0.01).The treatment group had lower levels of serum PAI and t-PA contents than the model group (P<0.01).

CONCLUSIONS

Huoxue Dingxuan Capsule glare can improve the blood flow of vertebral artery and reduce serum PAI and t-PA contents.

Medullary ischemia due to vertebral arteritis associated with Behçet syndrome: a case report

Here we report an extremely rare case of Behçet syndrome (BS) that showed acute onset of Wallenberg syndrome and was treated successfully by corticosteroids. A 51-year-old woman with BS had a sudden onset of Wallenberg syndrome. Three days after the onset, she was transferred to our institute. In the magnetic resonance imaging (MRI) study on admission, T2-weighted and fluid-attenuated inversion recovery images showed a high intensity area in the left paramedian region of the medulla oblongata. Contrast-enhanced T1-weighted images showed enhancement in the vessel wall of the left vertebral artery. We diagnosed her as having Wallenberg syndrome due to the acute vertebral arteritis associated with BS. After initiation of high-dose steroid therapy, her symptoms gradually improved. Two months after admission, she was discharged from our institute with mild hemihypesthesia. We hypothesized that vertebral arteritis due to BS had caused hypoperfusion of the medullary perforators causing Wallenberg syndrome in our patient.

[Observation of therapeutic effects on cervical vertigo treated with different methods]

OBJECTIVE

To compare the therapeutic effects of routine acupuncture, the electroacupuncture and the combined therapy of electroacupuncture and acupoint injection.

METHODS

Ninety-one cases were randomly divided into a routine acupuncture group (30 cases), an electroacupuncture group (31 cases), and a combined therapy of electroacupuncture and acupoint injection group (30 cases). Zusanli (ST 36), Fengchi (GB 20), Anmian (Extra), Taiyang (EX-HN 5), Hegu (LI 4), Yintang (EX-HN 3), Baihui (GV 20) and Sishengcong (EX-HN 1) were selected among 3 groups. Even manipulation was applied in routine acupuncture group; G 6805 electroacupuncture apparatus was added in electroacupuncture group; in combined therapy of electroacupuncture and acupoint injection group, electroacupuncture was applied, besides, Vitamin B12 0.5 mg and 0.2%/ Lidocaine 2 mL were injected at Fengchi (GB 20) and Anmian (Extra). Twenty treatments were given in 4 weeks. The changes of average blood flow of vertebral artery and basilar artery before and after treatment were observed and graded by the cervical vertigo syndrome and function score; the therapeutic effects were evaluated as well.

RESULTS

The average blood flow of vertebral artery and basilar artery, and the cervical vertigo syndrome and function score were improved in 3 groups (all P < 0.01), in which, it was more obvious in combined therapy of electroacupuncture and acupoint injection group than in others (P < 0.05, P < 0.01), and it in electroacupuncture group was superior to that in routine acupuncture group (P < 0.05). The effective rate was 63.3% (19/30) in routine acupuncture group, 80.6% (25/31) in electroacupuncture group and 90.3% (28/30) in combined therapy of electroacupuncture and acupoint injection group, indicating the significant differences among them (P < 0.05, P < 0.01).

CONCLUSION

The routine acupuncture, electroacupuncture, and combined therapy of electroacupuncture and acupoint injection are effective for cervical vertigo; the combined therapy is the best, and electroacupuncture comes second. It illustrates that the routine acupuncture, electroacupuncture, and combined therapy of electroacupuncture and acupoint injection have additive effects on treatment of cervical vertigo.

[Experimental study of eliminat dampness resolv phlegm method in treating cervical spondylopathy of the vertebral artery type]

OBJECTIVE

To detect the velocity and viscosity of blood flow of the vertebral arteries, the apoptotic cell and apoptotic related protein in the brain in order to offer theoretical foundation for the treatment of cervical spondylopathy of the vertebral artery type with the eliminat dampness resolv phlegm method.

METHODS

Sixty male Japanese big ear rabbits were divided randomly into normal sodium group (A), Flunarizine group (B), low dosage Wendantang group (C), large dosage Wendantang group (D), Flunarizine group combined with large dosage Wendantang group (E), normal group (F). Each group had 10 rabbits. Xiaozhiling injection was injected around the vertebral arteries of rabbits in group A, B C, D, E to make the model of the cervical spondylopathy of the vertebral artery type. Normal sodium (20 ml x kg(-1)d(-1)) was apply through intragastric administration in group A, F; Flunarizine (0.8 mg x kg(-1)d(-1)), low dosage Wendantang (1 g x ml(-1)d(-1)), large dosage Wendantang (2 g x ml(-1)d(-1)), Flunarizine combined with large dosage Wendantang were respectively apply through intragastric administration in group B, C, D, E. The velocity and viscosity of blood flow of the vertebral arteries, the apoptotic cell and apoptotic protein in the brain were detected before and after the treatment.

RESULTS

Satisfactory animal model were obtained in group A, B, C, D, E. The rabbits of group E had the most improvement of the velocity and viscosity of blood flow of the vertebral arteries while at meantime, which had the lowest apoptotic index and apoptotic related protein expression in the brain.

CONCLUSION

The routine treatment for the cervical spondylopathy of the vertebral artery combined with eliminat dampness resolv phlegm method could improve velocity and viscosity of blood flow of the vertebral arteries, which maybe relate with reduction of apoptosis in the brain.

Effects of tibolone on blood flow resistance and intima-media thickness of the carotid arteries: effect of time since menopause

OBJECTIVE

The aim of this prospective study was to evaluate the effects of tibolone on carotid atherosclerosis in healthy postmenopausal women.

METHODS

Twenty-five healthy postmenopausal women were included in the study. Patients received tibolone 2.5 mg daily for 6 months. Resistance indices of the common carotid artery (CCA), internal carotid artery (ICA), external carotid artery (ECA) and vertebral arteries, and intima-media thickness of the CCA were measured both at baseline and at the end of the study with ultrasonography.

RESULTS

No significant differences were observed in the resistance indices of the CCA, ICA, ECA and vertebral arteries, as well as intima-media thickness of CCA at 6 months in comparison with baseline. Tibolone significantly improved the intima-media thickness of the CCA of women who were less than 18 months since menopause.

CONCLUSION

Overall, these results demonstrate no significant effects of tibolone on either intima-media thickness or blood flow resistance in the carotid arteries in postmenopausal women. However, the results suggest that tibolone may have a positive effect on the vascular system if commenced within 18 months since menopause; this warrants further investigation.

Transcranial Doppler measurements in migraine and nitroglycerin headache

The objective of this study was to examine the cerebral circulation during spontaneous migraine attacks and to compare changes to an experimental headache model induced by nitroglycerin (NTG) infusion. This prospective study was carried out in a tertiary care hospital on migraineurs with or without aura. Healthy volunteers served as controls. There were no interventions. Flow velocity (FV) and pulsatility index (PI) were measured in migraineurs between and during headache attacks. In controls, FV and PI of the middle cerebral arteries were performed at baseline and after each IV infusion of 0.125, 0.25 and 0.5 microg/kg/min of NTG. In migraineurs, a significant increase in the mean flow velocity (MFV) in the left vertebral artery (VA) and the PI of the right VA during spontaneous migraine headache was found. In controls, all FV significantly decreased after infusion of NTG. The NTG model produces expected and substantially different vascular effects than those seen with spontaneous migraine headache.

Effect of Aerodiol administration on cerebral blood flow volume in postmenopausal women

OBJECTIVE

The aim of the study was to evaluate the acute effect of the intranasal 17beta-estradiol (Aerodiol, Servier, Chambray-les-Tours, France) administration on cerebral blood flow (CBF) volume.

METHODS

Eighteen healthy women who had been natural postmenopausal for at least 1 year were enrolled in the study. We conducted an experimental, randomized, placebo-controlled, crossover, double-blinded study of the acute effect of 17beta-estradiol on the internal carotid artery (ICA), vertebral artery (VA) and, CBF volume using color duplex sonography.

RESULTS

There were significant increases in the ICA, VA flow volumes and CBF volume after 17beta-estradiol administration compared to placebo measurements. However, there was no statistically significant difference in flow velocities or pulsatility indices.

CONCLUSION

Nasal 17beta-estradiol administration in postmenopausal women causes significant increases in CBF volume due to its vasodilatatory effect on ICA and VA.

Effects of aging on cerebral vasospasm after subarachnoid hemorrhage in rabbits

BACKGROUND AND PURPOSE

The effects of aging on cerebral vasospasm after subarachnoid hemorrhage (SAH) remain to be elucidated. The aim of this study was to clarify age-related differences of vasospasm and of papaverine reactivity in the responses of basilar arteries after SAH in rabbits.

METHODS

Rabbits receiving a single injection of arterial blood into the cisterna magna were divided into 3 groups: young (2 to 3 months old), adult (6 to 9 months old), and old (20 to 40 months old). Vertebrobasilar angiograms were obtained before SAH and 1, 2, 4, and 7 days after SAH. Papaverine was administrated selectively via the vertebral artery on day 2, and serial angiography was performed for up to 2 hours. Vessel structures were assessed with light microscopy on days 1, 2, 4, and 7 after SAH and at 10, 30, and 60 minutes after papaverine infusion.

RESULTS

Mortality from SAH in old rabbits was 40%, whereas that of young and adult rabbits was 0%. Angiograms revealed that SAH induced maximal constriction of the basilar arteries on day 2 in all age groups, and the constrictions were significantly increased with age at all time points investigated. The degree of dilatation of spastic basilar arteries after intra-arterial papaverine administration significantly decreased with age. Duration of the efficacy of papaverine became significantly shorter with age. Vessel diameter returned to the preinfusion value approximately 120, 60, and 30 minutes after infusion in young, adult, and old rabbits, respectively. Light microscopy in old rabbits showed luminal narrowing and corrugation of the internal elastic lamina not only in the basilar arteries but also in small arteries and intraparenchymal arterioles.

CONCLUSIONS

This study suggests that aging increases the degree of vasospasm in rabbits. The impaired reactivity to papaverine with aging might imply the early transition of the aged vessel to the papaverine-resistant chronic stage.

Cardiovascular pharmacological studies on JTV-506, a new potassium channel opener. 1st communication: effects on myocardium and vasculature

The effects of JTV-506 ((-)-(3S,4R)-2,2-bis(methoxymethyl)-4-[(1,6-dihydro-1-methyl-6-oxo-3- pyridazinyl)amino]-3-hydroxychroman-6-carbonitrile hemihydrate, CAS 170148-29-5), a novel coronary vasodilator, on hemodynamics, cardiac function and cardiac oxygen consumption were evaluated in anesthetized dogs. In anesthetized, open-chest dogs, JTV-506 (0.3-10 micrograms/kg i.v.) induced a marked increase in coronary blood flow in a dose dependent manner, while at these doses it had smaller effects on vertebral and mesenteric blood flow and almost no effect on renal blood flow. JTV-506 (1-10 micrograms/kg i.v.) showed a tendency to decrease oxygen consumption of the heart and elevate myocardial oxygen pressure without cardiac suppression. Effects of JTV-506 on hemodynamics and the respiratory system following i.v. administration (0.3-300 micrograms/kg) were investigated in spontaneously breathing anesthetized dogs. The effective dose to induce hemodynamic changes was more than 3 micrograms/kg. JTV-506 did not have a crucial influence on electrocardiogram. JTV-506 caused marked increase in coronary blood flow and myocardial oxygen pressure with slight change in blood pressure. It is concluded that JTV-506 is a potent vasodilator, with particularly pronounced effect on vasculature of the heart. These results suggest that JTV-506 may be useful in the treatment of angina pectoris.

Unusual cervical spinal cord toxicity associated with intra-arterial carboplatin, intra-arterial or intravenous etoposide phosphate, and intravenous cyclophosphamide in conjunction with osmotic blood brain-barrier disruption in the vertebral artery

BACKGROUND AND PURPOSE

When the clinical and radiologic characteristics of an unusual cervical spinal cord complication of intra-arterial (IA) chemotherapy with blood brain-barrier (BBB) disruption in the vertebral circulation are documented. Seven cases are reported and analyzed in search of a pathophysiologic explanation.

METHODS

We retrospectively identified 94 patients who received a total of 380 standardized regimens of IA carboplatin, IA or IV etoposide phosphate, and IV cyclophosphamide infusion in conjunction with osmotic BBB disruption of the vertebral artery. We describe seven of those patients in whom unexpected neck pain developed followed by neurologic symptoms primarily in the upper extremities.

RESULTS

The symptoms correlated with MR abnormalities (T1 hypointensity, T2 hyperintensity, and unusual contrast enhancement) in the cervical spinal cord, usually involving the gray matter. The neurologic deficits and MR changes were generally transient. One patient who received a flu vaccination 48 hours before the chemotherapy incurred progressive myelitis and expired.

CONCLUSION

The pathophysiology of this complication is probably multifactorial but may be related to vascular streaming and an atypical inflammatory toxic reaction to carboplatin and etoposide. The complication has not recurred during a 6-month period following modification of the protocol.

[Ultrasonic dopplerography in the diagnosis of vascular headache in children against a background of thiotriazoline treatment]

Overall twenty-four children aged 10 to 15 years suffering from headache were examined. Doppler sonography technique employed in the study of vessels of the brain and spine reveals a high level of anomalous vessels of the brain and spine in the absence of manifest hemodynamic disturbances in the arterial bed of the vertebral artery and in apparent changes in the venous system. Those patients with headache having been exposed to thiotriasoline treatment demonstrated a positive dynamics of indices for the venous circulation as evidenced by dopplerography.

Spinal cord protection by papaverine and intrathecal cooling during aortic crossclamping

AIM

To extend the safe period of aortic crossclamping in the porcine model by intrathecally dilating the spinal arteries, with cooling of the spinal cord, or using selfoteL METHODS: Experimental design and setting: prospective domestic laboratory pig study.

INTERVENTIONS

fifteen animals were assigned to a control group (C, N=5), intrathecal papaverine plus spinal cord cooling group (IP+C, N=5), or selfotel group (S, N=5). In the IP+C group, a lumbar laminectomy was performed and an intrathecal catheter placed for intrathecal injection of papaverine and perfusion with cold Ringer's solution (4 degrees C) prior to aortic crossclamping. In the selfotel group, 20 mg/kg of selfotel was administered 30 minutes before aortic crossclamping. In all 15 animals, the aorta was crossclamped for 60 minutes at normothermia.

MEASURES

immediately after the operation and 24 hours later, lower limb function was evaluated.

RESULTS

All five control animals were paralyzed; all 5 IP+C animals could stand or walk (p=0.004 versus control); and in the selfotel group, one had paraparesis, three had paraplegia and one died before evaluation (p=n.s.)

CONCLUSIONS

The combination of intrathecal papaverine to dilate spinal arteries and prevent spasm from the cold solution plus intrathecally cooling the spinal cord appears to extend the period of safe aortic crossclamping. Selfotel, in this model of extended, severe, spinal cord ischemia, was ineffective.

Blood flow velocity changes in carotid and vertebral arteries with stellate ganglion block: measurement by magnetic resonance imaging using a direct bolus tracking method

BACKGROUND AND OBJECTIVES

Stellate ganglion block (SGB) leads to vasodilation of the head and neck, as a result of a regional sympathetic blockade. However, in such cases, controversy remains concerning changes in cerebral and extracerebral blood flow in the head. We estimated the effect of SGB on blood flow in the head by measuring the blood flow velocity in cervical vessels, using magnetic resonance imaging and the direct bolus tracking method. This noninvasive method is free from potential artifacts of bones and other connective tissues.

METHODS

Seven adult patients with acute or chronic pain in the head or neck underwent SGBs, using an anterior paratracheal approach with 6-8 mL of 1% mepivacaine (3 right and 4 left SGBs). Blood flow velocity in common carotid and vertebral arteries (CCA and VA) was measured simultaneously before and after SGB, using the direct bolus tracking method.

RESULTS

On the side of SGB, blood flow velocity in CCA significantly increased (P < .002), whereas velocity in VA was unchanged after SGB. On the side contralateral to the SGB, significant changes in blood flow velocity in CCA and VA were never observed.

CONCLUSIONS

Blood from the VA flows primarily to cerebral vessels, whereas that from CCA goes to both cerebral and extracerebral vessels. Given the presumed differences in blood flow distribution through the VA and CCA, we assume that the observed CCA blood flow increases, ipsilateral to the SGB, primarily as a result of vasodilation of extracerebral vessels and independent of changes in brain blood flow.

Spontaneous healing of cervical pseudoaneurysm in vertebral artery dissection under anticoagulant therapy

We report a 41-year-old woman with embolic stroke of the mid-pons attributed to embolism from vertebral artery dissection. Angiography revealed an occluded artery on one side and an incidental pseudoaneurysm of the midcervical portion of the vertebral artery on the other. After 3 months of warfare in therapy control angiography showed complete occlusion of the pseudoaneurysm. We discuss therapeutic choices and review the literature.

Global cerebral blood flow during infusion of adenosine in humans: assessment by magnetic resonance imaging and positron emission tomography

Adenosine, an endogenous vasodilator, induces a cerebral vasodilation at hypotensive infusion rates in anaesthetized humans. At lower doses (< 100 micrograms kg-1 min-1), adenosine has shown to have an analgesic effect. This study was undertaken to investigate whether a low dose, causing tolerable symptoms of peripheral vasodilation affects the global cerebral blood flow (CBF). In nine healthy volunteers CBF measurements were made using axial magnetic resonance (MR) phase images of the internal carotid and vertebral arteries at the level of C2-3. Quantitative assessment of CBF was also obtained with positron emission tomography (PET) technique, using intravenous bolus [15O]butanol as tracer in four of the subject at another occasion. During normoventilation (5.4 +/- 0.2 kPa, mean +/- s.e.m.), the cerebral blood flow measured by magnetic resonance imaging technique, as the sum of the flows in both carotid and vertebral arteries, was 863 +/- 66 mL min-1, equivalent to about 64 +/- 5 mL 100 g-1 min-1. The cerebral blood flow measured by positron emission tomography technique, was 59 +/- 4 mL 100 g-1 min-1. All subjects had a normal CO2 reactivity. When adenosine was infused (84 +/- 7 micrograms kg-1 min-1.) the cerebral blood flow, measured by magnetic resonance imaging was 60 +/- 5 mL 100 g-1 min-1. The end tidal CO2 level was slightly lower (0.2 +/- 0.1 kPa) during adenosine infusion than during normoventilation. In the subgroup there was no difference in cerebral blood flow as measured by magnetic resonance imaging or positron emission tomography. In conclusion, adenosine infusion at tolerable doses in healthy volunteers does not affect global cerebral blood flow in unanaesthetized humans.

Arterial changes after thrombolysis and percutaneous transluminal angioplasty in vertebrobasilar thrombosis

We present clinicopathologic findings in a patient treated with intraarterial thrombolysis and angioplasty for vertebrobasilar thrombosis. Autopsy revealed a marked inflammatory infiltrate within the vertebral artery at the site of catheter manipulation. This finding may have important implications for the use of interventional angiography in cerebrovascular disease.

Extracranial intravascular vasodilatory response to acetazolamide and magnetic resonance angiography

Cerebral vasodilatory testing provides an important measure of both the hemodynamic significance of arterial occlusive disease and the adequacy of collateral pathways. This study measured the extracranial intravascular volume flow rate response to acetazolamide using phase-contrast magnetic resonance angiography. From 10 patients with unilateral carotid transient ischemic attacks (TIAs), a total of 18 extracranial carotid arteries (10 symptomatic, 8 asymptomatic, 2 occluded) and 19 extracranial vertebral arteries were studied. Patients were free of large-vessel intracranial stenoses, evident areas of ischemic infarction, evident areas of nonspecific white matter change, and hemodynamic or low-flow induction of TIA symptomatology. Asymptomatic carotid volume flow rates rose from 151 +/- 19 (standard error of mean) to 220 +/- 26 ml/min while symptomatic flow rates rose from 106 +/- 22 to 145 +/- 25 ml/min. Dominant vertebral volume flow rates rose from 128 +/- 23 to 160 +/- 22 ml/min while nondominant rates rose from 40 +/- 12 to 61 +/- 15 ml/min. Carotid volume flow rates were inversely proportional to percent stenosis for both baseline (r = 0.51, p < 0.02) and acetazolamide (r = 0.81, p < 0.001) data. Baseline-plus-acetazolamide volume flow rate techniques safely measure intravascular vasodilatory responses. Intracranial measurement techniques are being developed to further study cerebrovascular reserve using phase-contrast magnetic resonance angiography.

Acetylcholine induces contraction in vergebral arteries from treated hypertensive patients

Endothelium-dependent vasodilatation to acetylcholine is abnormal in animal models of hypertension. This abnormality reflects a change in the balance of relaxing and contracting factors produced in the vascular wall. In human cerebral arteries, endothelin has been implicated in the abnormal vasoconstrictor response following subarachnoid hemorrhage. This study tests the hypothesis that cerebral arteriolar dilatation to acetylcholine reduced in clinical hypertension due to an overproduction of endothelin. Our results show that at high concentrations of muscarinic agonist (0.3-3 microM), human vertebral arteries from hypertensive patients contract whereas those from normotensive patients remain maximally dilated. We conclude that the normal dilator response to acetylcholine is abrogated in vertebral arteries from treated hypertensive patients but endothelin-1 does not contribute to the abnormal responsiveness.

The effects of pituitary adenylate cyclase-activating polypeptide on cerebral arteries and vertebral artery blood flow in anesthetized dogs

We investigated and compared the effects of pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) on cerebral circulation in anesthetized dogs. The intracisternal administration of PACAP-27, PACAP-38, and VIP dilated canine cerebral arteries in a dose-dependent manner. A 10 nmol dose of PACAP-27, PACAP-38, and VIP dilated the basilar artery by 23 +/- 3, 27 +/- 3 and 30 +/- 3%, respectively. Rostrally located arteries tended to be more responsive to PACAP-27. Pretreatment with NG-monomethyl-L-arginine did not affect PACAP-27-induced vasodilation. Vertebral artery blood flow was also affected by intra-arterial injection of these peptides in a dose-dependent manner. A 100 pmol dose of PACAP-27, PACAP-38, and VIP increased the vertebral artery blood flow by 42 +/- 10, 29 +/- 4, and 62 +/- 11%, respectively. The VIP receptor antagonist, [Lys1,Pro2,5,Arg3,4,Tyr6]VIP, inhibited both the VIP- and PACAP-38-induced increase in vertebral artery blood flow. These findings suggest that PACAP plays a role in the regulation of cerebral circulation.

Vertebral artery dissection with bilateral hemiparesis

Right vertebral artery dissection after trauma, with subsequent cerebellar and thalamic infarcts, is described in a 5-year-old child who presented with mild hemiparesis and ataxia. This vascular injury has been more commonly reported in adults. The diagnosis was confirmed with magnetic resonance imaging of the brain and cerebral magnetic resonance angiography. An arterial thrombus with multiple embolization was the cause of the child's neurologic deficits. Traumatic injury to the posterior circulation should be considered in children who have signs of vertebrobasilar insufficiency.

Vasopressin mediated vasodilation of cerebral arteries

The bolus injection of vasopressin into the vertebral artery produced a dose-dependent vasodilation in the major cerebral arteries, detected angiographically, while it elicited a decrease in vertebral blood flow. One nanomol of vasopressin was the optimal dose for producing maximal vasodilation. The basilar, posterior communicating, and internal carotid arteries showed the most dilatation, followed by the middle cerebral, the intracranial portion of the vertebral artery and the anterior spinal artery. The extracranial portion of the vertebral artery was less sensitive to vasopressin. The vasodilation was inhibited by a V1-antagonist and NG-monomethyl-L-arginine. These results suggest that the arteries of the circle of Willis at the base of the brain are more sensitive to nitric oxide release induced by vasopressin compared with other intracranial and extracranial arteries.

Transient severe brain stem depression during intraarterial papaverine infusion for cerebral vasospasm

A 63-year-old woman had severe, symptomatic cerebral vasospasm secondary to subarachnoid hemorrhage. We initiated simultaneous infusions of papaverine into her left vertebral and left internal carotid arteries. Twenty-five minutes after the infusions had begun, the patient had a transient reaction of respiratory arrest followed by rapid, progressive loss of brain stem function.

[Idiopathic cupulolithiasis: vasomotor reactivity evaluation of the vertebro-basilar artery by transcranial doppler ultrasonography and acetazolamide test]

Benign paroxysmal positional vertigo (BPPV) or cupulolithiasis is one of the more common peripheral vestibular disorders. Diagnosis is made on the observation of typical positioning nystagmus brought about by the Hallpike manoeuver. In most cases of BPPV, etiology is unknown. Microcirculatory disorders have often been considered responsible for idiopathic BPPV. Few reports have been published on this specific aspect of the problem. In our study we evaluated vertebro-basilar haemodynamics and vasomotory reactivity after Acetazolamide administration in 12 patients with idiopathic BPPV. The results obtained reveal the absence of macrocirculatory impairment in the vertebro-basilar district in basal conditions, but significative vasoreactivity variation after acetazolamide, both in vertebral and basilar arteries. Poor vasomotor reactivity in one vertebral artery was observed in 5 patients and, in two cases, in the basilar artery. Altered vasoreactivity in the middle cerebral arteries was not observed in any case. In the light of these findings, we suggest that a possible inadequate response if microcirculation in the labyrinth, in some particular haemodynamic situations, might cause otolithic damage.

Selective vasodilatory effect of dipfluzine on vertebral artery in anesthetized dogs

Dipfluzine (Dip) is a novel calcium antagonist first developed by Department of Chemistry, Beijing University. The effects of Dip on hemodynamics and vascular resistance in vertebral (VVR), coronary (CVR), and femoral (FVR) arteries were compared with those of cinnarizine (Cin) in anesthetized dogs. Dip iv decreased dose-dependently VVR at 0.1, 0.3, 1, and 3 mg.kg-1, CVR at 3 mg.kg-1, and FVR at 1 and 3 mg.kg-1. The fall of VVR by Dip iv was more remarkable than that by Cin at the matching doses. The systolic, diastolic, and mean blood pressure and total peripheral resistance were temporarily reduced equally by both of them at 1 mg.kg-1 iv, while Dip and Cin produced no obvious changes in heart rate, cardiac index, stroke index, LVP, and dP/dtmax at all doses. These results suggested that Dip possessed a high selectivity at different sites of the vasculature and was a more potent selective cerebral vasodilator than Cin.

[Effects of tetramethylpyrazine on rabbit basilar artery ring and canine vertebroarterial circulation]

Tetramethylpyrazine (TMP) inhibited the contraction of rabbit basilar artery and mesenteric arteries caused by KCl with an IC50 of 1.3 mmol.L-1 and 7.5 mmol.L-1 (P < 0.01). The contraction of the rabbit basilar and mesenteric artery ring evoked by KCl, CaCl2 and norepinephrine was inhibited noncompetitively by TMP with the pD2' values of 2.18 +/- 0.16 and 1.83 +/- 0.18 (P < 0.01), 2.13 +/- 0.12 and 2.08 +/- 0.12 (P > 0.05), 3.08 +/- 0.16 and 2.57 +/- 0.08 (P < 0.01), respectively. The contraction of rabbit basilar artery and saphenous veins evoked by 5-HT was also inhibited by TMP with an IC50 of 0.22 mmol.L-1 and 2.2 mmol.L-1 (P < 0.01), respectively. TMP antagonized the myogenic activity of rat portal vein strips. TMP increased canine vertebroarterial blood flow and had no effect on femoral artery blood pressure. The results suggested that TMP may block the calcium channel, inhibit the contraction of rabbit basilar artery, and improve the canine vertebroarterial circulation selectively.

Effects of vasopressin and oxytocin on canine cerebral circulation in vivo

In vivo experiments on the vasoactive effects of vasopressin and oxytocin on cerebral circulation were carried out in anesthetized dogs, using an electromagnetic flowmeter to measure vertebral blood flow and angiography to measure the internal diameter of the basilar artery. Direct bolus infusion of 1 pmol to 1 nmol of vasopressin or 10 pmol to 10 nmol of oxytocin into a femoral-vertebral artery shunt produced a dose-dependent decrease in vertebral artery blood flow without significantly affecting mean arterial blood pressure. Vasopressin was more potent than endothelin and neuropeptide Y, which have also been demonstrated to induce long-lasting decreases in vertebral artery blood flow. However, direct bolus infusion of vasopressin (100 pmol and 1 nmol) or oxytocin (1 nmol and 10 nmol) into the vertebral artery dilated major vessels including the vertebral, anterior spinal, and basilar arteries, as well as the circle of Willis and its main branches, while endothelin (1 nmol) and neuropeptide Y (5 nmol) caused no change in the diameters of major cerebral arteries. The V1 antagonist d(CH2)5tyrosine(methyl) arginine vasopressin suppressed the effects of both vasopressin and oxytocin. Vasopressin was over 10 times as potent as oxytocin in both assays. The vasodilatory effect of vasopressin, which may be mediated by an endothelium-dependent mechanism, was functionally damaged in dogs after experimental subarachnoid hemorrhage. These data suggest regional differences in the sensitivity and responsiveness of vasculature to vasopressin and oxytocin, and specifically that both peptides act through V1 receptors to decrease the resistance of large vessels and increase the resistance of small vessels.

Oscillatory contractions in vertebral arteries from hypertensive subjects

In response to several agonists, tail arteries from spontaneously hypertensive stroke prone rats (SHRSP) contract in an oscillatory manner not observed in tail arteries from normotensive rats. This study evaluated whether oscillations in force development characterize the contractile pattern of vertebral arteries from hypertensive humans. Vertebral arteries were isolated and studied within 18-24 h post mortem. Helical strips of the arteries were mounted in a muscle bath for isometric force recording. Contractile responses to serotonin (10(-7)M) and endothelin (10(-8)M) in arteries from hypertensive subjects were characterized by fluctuations in force development whereas those in arteries from normotensive subjects usually remained constant with time. The frequency of the response was approximately 1-2 contraction/relaxation cycles per min. This pattern of oscillatory contractile activity was observed in all but one of the hypertensive arteries (n = 15), and in approximately 40% of the normotensive arteries (n = 12). Oscillatory activity was converted to maintained contraction by nifedipine (10(-7)M) which also caused relaxation of the contractile response. Relaxation to acetylcholine (10(-6)M) and nitroglycerin (10(-6)M) did not alter the oscillatory contractions. Endothelium removal did not influence the oscillatory pattern of contraction. These observations suggest that oscillatory contractile activity in vertebral arteries from hypertensive subjects is related to abnormal calcium entry into the smooth muscle cells. This altered membrane property may contribute to changes in vascular reactivity in hypertension.

Cerebral vascular effects of peptide histidine methionine in canine and bovine species

Peptide histidine methionine (PHM) is a neuropeptide with structural homology to vasoactive intestinal peptide (VIP), itself a putative vasodilatory neurotransmitter. Intra-arterial administration of PHM caused a transient, dose-dependent increase in canine vertebral artery blood flow in vivo. PHM was less potent in this effect than VIP. The interaction of PHM with the vasoconstrictor amines, norepinephrine, histamine, and serotonin, was examined using isolated strips of the bovine middle cerebral artery. PHM shifted the concentration-response curves for vasocontraction by norepinephrine and histamine to the right but did not affect the vasocontraction induced by serotonin. These results suggest that PHM may have a role in the regulation of the cerebral circulation.

Endothelin causes contraction of canine and bovine arterial smooth muscle in vitro and in vivo

We have studied the effect of endothelin, an endothelium-derived peptide, on isolated canine and bovine cerebral arteries in vitro and on canine vertebral blood flow (VBF) in vivo. Endothelin produced a dose-dependent contraction of canine and bovine arterial smooth muscle with ED50 values ranging from 4 to 8 nM. The response to endothelin developed slowly and persisted as a sustained contraction. Maximal contraction by endothelin required the presence of extracellular calcium and was independent of the presence of endothelium. The maximal contraction produced by endothelin was approximately 2-3 times greater than that produced by neuropeptide Y or angiotensin II. The injection of endothelin into the vertebral artery decreased vertebral blood flow (VBF) dose-dependently without affecting systemic blood pressure or heart rate. The decrease in VBF produced by endothelin was long-lasting, like that produced by neuropeptide Y, but more potent. The present data, together with our previous study demonstrating that the intracisternal injection of endothelin induces an unusually long-lasting decrease in the basilar artery diameter angiographically, suggests that endothelin may act as a long-lasting vasoconstrictor in cerebral vascular disease.

Effects of calcitonin gene-related peptide on canine cerebral artery strips and the in-vivo vertebral blood flow in dogs

The effects of calcitonin gene-related peptide (CGRP) on canine cerebral arteries and on vertebral blood flow were investigated in-vivo and in-vitro and the findings compared with the effects of vasoactive intestinal peptide (VIP) and substance P. Administration of CGRP into the vertebral artery caused a dose-dependent and long-lasting increase in blood flow. The in-vivo vasodilatory effects of substance P and VIP were short-lasting. CGRP (0.1 to 100 nmol/l) elicited a concentration-dependent relaxation of the isolated middle cerebral and basilar arteries when the tissues were precontracted by exposure to prostaglandin F2 alpha (PGF2 alpha). This effect was not antagonized by propranolol, atropine, tetrodotoxin, (N-Ac-Tyr1, D-Phe2)-growth hormone-releasing factor(1-29)-NH2 or (D-Pro2, D-Trp7,9) substance P. CGRP also reduced concentration-dependently the contraction of cerebral arteries induced by KCl or 9,11-epithio-11,12-metano-thromboxane A2 (STXA2). Mechanical removal of the endothelium did not abolish the vasodilatory response to CGRP. In PGF2 alpha-contracted canine cerebral arteries, VIP (0.1 to 100 nmol/l) was less potent a vasodilator than CGRP. At low concentrations (0.01 to 1 nmol/l) substance P elicited a rapid and short-lasting relaxation, and in the absence of endothelium this relaxation disappeared. These findings are clear evidence that CGRP modulates vascular tone.

A possible mechanism on the potentiated vascular effect of coadministration of ifenprodil tartrate and calcium hopantenate: a study in the basilar and vertebral arteries

In our earlier report [Shibuya et al. in press], we demonstrated the partial mechanism of the synergism between ifenprodil tartrate and calcium hopantenate on cardiovascular diseases. The mechanisms of the synergistic effects in the basilar and vertebral arteries were further studied in this paper using our described methods. Ifenprodil tartrate produced a sustained increase in the vertebral arterial blood flow of rats, while calcium hopantenate. Ifenprodil tartrate caused dose-related relaxation of K+-induced contractions in by ifenprodil tartrate was significantly enhanced by the coadministration of calcium hopantenate. Ifenprodil tartrate caused dose-related relaxation of K+-induced contractions in isolated canine basilar arteries, while calcium hopantenate had no effect. The dose-relaxation curve of ifenprodil tartrate was shifted to the left by pre-incubation in calcium hopantenate. In K+-depolarized basilar arteries, ifenprodil competitively antagonized the response to Ca2+, and this was enhanced by pre-incubation in calcium hopantenate. Ifenprodil tartrate inhibited K+-induced Ca2+ uptake in canine cerebral arteries and this was enhanced by pre-incubation in calcium hopantenate. These results suggest that the enhancement by calcium hopantenate of the ifenprodil tartrate effect on the vertebral blood flow is due to increased vascular relaxation through the inhibition of Ca2+ influx.

Heterogeneous vasomotor responses of anatomically distinct feline cerebral arteries

1. The vasomotor reactivity to a number of neurotransmitters and blood-borne substances was evaluated in several anatomically distinct arteries of the cat cerebral circulation. Few regional differences were observed in their vasoconstrictor responses to noradrenaline, dopamine, 5-hydroxytryptamine and prostaglandin F2 alpha. Only the anterior cerebral artery reacted strongly to all vasoconstrictor agents. 2. Adenosine, acetylcholine and histamine induced pronounced relaxation in the vast majority of the major cerebral arteries. The relaxation elicited by adenosine showed a slight degree of heterogeneity between the arteries and the overall response accounted for 81 +/- 6% of the pharmacologically-induced tone. On the other hand, the dilatation induced by acetylcholine and histamine varied as a function of the anatomical localization of the cerebral arteries. The acetylcholine-induced vasodilatation was significantly more pronounced in the middle cerebral, anterior communicating and anterior cerebellar arteries, with respective responses of 72, 66 and 83% of the induced tone as compared to 43% in the other vessels. However, all arteries were equally sensitive to acetylcholine with an overall mean pD2 value of 7.47 +/- 0.06. The most heterogeneous results were obtained with histamine and applied both to the magnitude of the maximal response and the sensitivity of the various arteries to this amine. The intensity of the relaxation varied from 20% (anterior communicating artery) to 118% (posterior cerebellar artery). 3. Among the neuropeptides studied, substance P and bradykinin were considerably less potent than vasoactive intestinal peptide on all the cerebral arteries. The least responsive vessel to bradykinin was the anterior cerebral artery with a maximal response of 22 +/- 5% of the induced-tone and a pD2 value of 7.56 +/- 0.24. All vessels responded weakly to substance P and those from the vertebrobasilar circulation were significantly less sensitive to this neuropeptide with pD2 values around 8.07 as compared to 9.82 in the more rostral arteries. Although all vessels were equally sensitive to vasoactive intestinal peptide, the dilator responses were significantly less pronounced in the middle cerebral and basilar arteries (maximal response of 86 +/- 5% and 69 +/- 6% of the induced-tone, respectively, as compared to 110 +/- 9% in the other vessels). 4. The vertebrobasilar arteries were as reactive, if not more reactive, to vasoconstrictors than the vessels originating from the carotid circulation. In contrast, the dilator responses were less marked in most caudal arteries. Such dichotomies may be important in the regulation of local cerebral blood flow. 5. The results emphasize the considerable heterogeneity in the vasomotor responses to a given substance among the various cerebral arteries. Further, they suggest the presence of multiple receptor populations which mediate opposite effects and which are distributed in different proportions among the cephalic arteries.

Responses of renal, coronary and vertebral vasculatures to MC-838 and captopril in anesthetized dogs

The regional hemodynamic effects of MC-838, a new angiotensin-converting enzyme inhibitor, and captopril at equidepressor doses were examined in the anesthetized dog by simultaneously measuring renal (RBF), coronary (CBF), vertebral (VBF) arterial and aortic blood flow (AoF). Hemodynamic responses to angiotensin I (AI), AII and noradrenaline were compared before and after the administration of each inhibitor. MC-838 (3 mg/kg i.v.) lowered gradually aortic pressure (AoP) and increased moderately AoF and RBF up to 60 min after the administration. Captopril (0.1 mg/kg i.v.) lowered AoP immediately after the administration and increased AoF and RBF more shortly than MC-838. Neither inhibitor produced a marked change in VBF or CBF. The effects of the inhibitors in the renal vascular bed was much greater than that in vertebral and coronary vascular beds, although vascular resistance in all of them was significantly reduced. Each of the drugs inhibited the pressor and renal vasoconstrictor responses to AI. These results indicate that the renal vasculature is more sensitive to both MC-838 and captopril than vertebral and coronary vasculature, but MC-838 has a slower and longer-lasting action than does captopril.

The effects of piperidine and its related substances on blood vessels

Piperidine is an endogenous active amine. Intravenous or intra-arterial administration of piperidine produced vasodilation in anesthetized dogs. The vasodilative effect of piperidine was inhibited by atropine (0.3 mg/kg, i.v.). In the hind limb perfusion experiment in anesthetized dogs, piperidine produced vasodilation, while it showed no vasorelaxing action in various isolated canine arterial strip preparations. These results suggest that the vasodilation caused by piperidine may be produced through activation of muscarinic receptors and that piperidine may act on smaller resistance blood vessels but not on large conductance vessels. In addition, pipecolic acid and N-methyl piperidine, the respective precursor amino acid and metabolite of piperidine, were almost inactive, but nipecotic acid was 1/4 to 1/10 times as active as piperidine as vasodilators. It is suggested that the non-substituted amine moiety of piperidine is very important for the manifestation of vasodilative activity and that piperidine might play a role in regulation of peripheral vascular circulation.

Low pharmacological responsiveness of the vertebro-basilar circulation in Macaca nemestrina monkeys

We have examined the responsiveness of the vertebro-basilar circulation of the anesthetized Macaca nemestrina monkey to vasoactive agents infused directly into the artery. Infusion of noradrenaline caused a slight increase in vertebral arterial resistance. This constriction was less than that seen in previous experiments with either the internal or vertebral arterial resistance. This constriction was less than that seen in previous experiments with either the internal or external carotid arteries. In the presence of vasodilatation caused by inhalation of a CO2-rich gas mixture, this constriction became a dilatation. Serotonin was without significant effect on the vertebral arterial bed. Bradykinin, histamine and prostaglandin E1 all produced slight dilatation, with bradykinin being the most potent. In all cases the concentration required to produce an effect on the vasculature was much greater in the vertebral circulation than it is in the internal carotid and extracerebral circulations. We conclude that the intact vertebro-basilar circulation is much less sensitive to vasoactive agents than experiments with isolated segments of these arteries would indicate and that therefore these agents are unlikely to play a significant part in the pathogenesis of vertebro-basilar migraine.

Vasodilator and hypotensive effects of the optical isomers of nicardipine (YC-93), a new Ca2+-antagonist

Vasodilator and hypotensive effects of (+) and (-) nicardipine were investigated in anesthetized dogs. When administered intravenously, (+) nicardipine was 3 times as potent as the (-) isomer in increasing vertebral blood flow and in lowering mean blood pressure. When injected into the vertebral artery, (+) nicardipine was also 3 times as potent as the (-) isomer in increasing vertebral blood flow. Upon both routes of administration, the duration of the action after (+) nicardipine was longer than that after the (-) isomer. However, there were no differences of plasma nicardipine levels after intravenous injection of both isomers to conscious beagle dogs. The LD50 values of (+) nicardipine in mice and rats upon intravenous injection were only 1.5-2 times smaller than those of the (-) isomer. These results indicate that there exists a stereoselectivity of vasodilator and hypotensive actions among the nicardipine isomers.

[Effects of (E)-1-[bis (4-fluorophenyl)methyl]-4-(3-phenyl-2-propenyl) piperazine dihydrochloride(flunarizine) on cerebral circulation]

Effects of flunarizine (0.3-3 mg/kg, i.v.) on cerebral circulation were compared with those of cinnarizine (0.3-3 mg/kg, i.v.) and papaverine (0.1-1 mg/kg, i.v.) in anaesthetized dogs and cats. In dogs any of the three drugs caused a dose-related increase in vertebral, common carotid, and femoral arterial blood flow, while a transient decrease in renal blood flow was seen. In particular, the vasodilatation caused by flunarizine and cinnarizine was much more marked in the vertebral vascular beds as compared to the other ones. Flunarizine (10 and 30 mg/kg, intraduodenally) caused a greater and more prolonged increase in the vertebral blood flow than cinnarizine and papaverine did when they were used in the same doses. Concerning the local circulation in cats, flunarizine and cinnarizine produced a marked flow increase in the cerebellar cortex, and apparent blood flow and pO2 increases in the cerebral cortex with no observable concomitant changes in arterial blood pO2 and pCO2; but a slight decrease in hippocampal blood flow without any consistent effect in hypothalamic blood flow. In this study, flunarizine was shown to have a more prolonged pharmacological activity on the responses of the cerebral circulation than equal doses of cinnarizine or papaverine.

[Effects of diltiazem on hemodynamics and His bundle electrogram in the anesthetized dog (author's transl)]

Effects of diltiazem, a calcium antagonist, on the cardiovascular system in the pentobarbital anesthetized dogs were investigated. Diltiazem (100 micrograms/kg and 300 micrograms/kg, i.v.) decreased blood pressure, heart rate and total peripheral resistance, while cardiac output and stroke volume were markedly increased. The max dp/dt of left ventricular pressure tended to increase with a dose of 100 micrograms/kg. Left ventricular end-diastolic pressure was slightly increased with a dose of 400 micrograms/kg. Rate pressure product was significantly reduced. Diltiazem (30 micrograms/kg and 100 micrograms/kg) increased pulmonary arterial flow together with the increase in both systolic and diastolic pulmonary arterial pressure. Diltiazem (100 micrograms/kg) increased common carotid, femoral and superior mesenteric arterial blood flow by 30 to 40%, whereas vertebral blood flow was increased by over 100%. The dose dependency in the vertebral blood flow was remarkable. Response of the vertebral artery to diltiazem was similar to that reported in the case of the coronary artery. In the His bundle electrogram, diltiazem increased the AH interval by about 10% at 100 micrograms/kg and 25% at 200 micrograms/kg, without changing the HV interval. Diltiazem-induced AH prolongation was completely depressed by epinephrine but only partially so by CaCl2. Thus, the effects of diltiazem on sinus rhythm and AV conduction in the anesthetized dog were more potent than the effects on cardiac contractility, although weaker than the effects of the vasodilating action. The vasodilator effects appear to be the primary action of diltiazem on the cardiovascular system.

Transient responses of rabbit cerebral blood vessels to norepinephrine: correlation with intrinsic myogenic tone

Transient contractile responses to norepinephrine (NE) of vascular segments from the rabbit vertebral, internal carotid, and basilar arteries rise to a peak within several seconds, and in the presence of the agonist, reverse rapidly, relaxing with a half-time of 15 +/- 3.2 seconds. In the basilar artery, peak contraction is approximately 25% of the maximum response mediated via the "alpha-like" adrenoreceptors and is elicited by NE 10(-7) M. Steady state contractions are seen with higher concentrations. Transient contractile responses are absent in segments from the brachiocephalic and external carotid arteries, and their incidence increases the more rostral along the length of the vertebral and internal carotid artery the origin of the segment studied. They were seen in all preparations of the intracranial vertebral and basilar arteries. There is a good correlation between the occurrence in any particular vascular segment of the transient contractile response and intrinsic tone as assessed by relaxation to papaverine (10(-6) M). The response was blocked by alpha-adrenergic receptor blocking agents and was not elicited by d-NE nor tetrahydrazoline or oxymetazoline. This response may be analogous to the first phase of the biphasic contraction found in many other blood vessels. Since in cerebral vessels the agonist concentration to elicit the first phase is several orders of magnitude lower than the second, it can appear in the absence of the latter.

Comparative responses of the carotid and vertebral arterial systems of rhesus monkeys to betahistine

A newly developed photoelectric method was used in 5 rhesus monkeys to measure the mean transit time of blood through the carotid and vertebral arteries, together with measurement of the blood flow through the tissues of the fronto-parietal area supplied by the carotid artery and of the cerebellar tonsil supplied by the vertebral artery. Following intravenous administration of betahistine mesylate, a histamine analog, the mean transit times of blood through the 2 arteries were equally shortened by 10%, despite a 20% decrease in the mean arterial blood pressure (P less than 0.05). The cerebral tissue and cerebellar tissue blood flow was increased by betahistine, from 70.4 to 81.4 ml/100g/min and from 73.2 to 84.0 ml/100g/min, respectively. Since histamine has been reported to produce a decrease in cardiac output, the increase in cerebral blood flow confirmed that betahistine is a selective cerebral vasodilating agent. However, by comparing the hemodynamic data for the two cerebral arterial systems, it can be concluded that the responses of the carotid and vertebral arterial systems to the vasodilating action of betahistine were essentially the same in extent.

[Vasodilator action of (+/-)-1-(3, 4, 5-trimethoxybenzyl)-6-hydroxy-1, 2, 3, 4-tetrahydroisoquinoline hydrochloride (CV-705) in anesthetized dogs (author's transl)]

The vasodilator action of CV-705 was investigated in a number of vascular regions of anesthetized mongrel dogs and this action was compared with that of papaverine. When CV-705 was administered intravenously the vertebral, common carotid and internal carotid blood flow was increased considerably and was long-lasting. These effects were most remarkable among the regions tested. Femoral, aortic and coronary blood flow were also increased. On the other hand, the blood flow through superior mesenteric artery and portal vein increased only slightly. Renal blood flow was decreased slightly after an intravenous administration, whereas an increase was observed after an intra-arterial administration. Such a regional distribution of blood flow after CV-705 was quite similar to that observed with papaverine. CV-705 was well absorbed through the digestive tract. CV-705 given intravenously showed a weak hypotensive and positive chronotropic action. The increase in common carotid blood flow induced by intra-arterial administration of CV-705 was not affected by pre-treatment with atropine or triprolidine, but was partially suppressed by pre-treatment with propranolol. These results suggest that CV-705 has a papaverine-like action as well as a weak beta-adrenoceptor stimulating action, consequently a vasodilator action occurs.

[Different sensitivities of cerebral arterial systems to noradrenaline]

The tests carried out on the nonanesthetized and anesthetized cats showed noradrenaline to exert a direct influence on the cerebral vessels, increasing their tone. The drug produced different effect on the vessels of different arterial systems of the brain. Noradrenaline increased the resistance of the carotid arteries to a greater degree than in the vertebral arterial system.