Acetazolamide as a vasodilatory stimulus in cerebrovascular diseases and in conditions affecting the cerebral vasculature

Pathologic processes affecting the brain vessels may damage cerebral vasodilatory capacity. Early detection of cerebral dysfunction plays an important role in the prevention of cerebrovascular diseases. In recent decades acetazolamide (AZ) has frequently been used for this purpose. In the present work the mechanism of action and the previous studies are reviewed. The authors conclude that AZ tests are useful in cerebrovascular research. Further investigations are recommended to prove how impaired reserve capacity and reactivity influence the stroke risk in patients and whether these tests may indicate therapeutic interventions.

Co-localisation of kisspeptin with galanin or neurokinin B in afferents to mouse GnRH neurones

The gonadotrophin-releasing hormone (GnRH) secreting neurones, which form the final common pathway for the central regulation of reproduction, are directly targeted by kisspeptin (KP) via the G protein-coupled receptor, GPR54. In these multiple labelling studies, we used ovariectomised mice treated with 17β-oestradiol (OVX + E(2)) or vehicle (OVX + oil) to determine: (i) the ultrastructural characteristics of KP-immunoreactive (IR) afferents to GnRH neurones; (ii) their galanin or neurokinin B (NKB) content; and (iii) the co-expression of galanin or NKB with KP in the two major subpopulations of KP neurones located in the rostral periventricular area of the third ventricle (RP3V) and the arcuate nucleus (Arc). Electron microscopic investigation of the neuronal juxtapositions revealed axosomatic and axodendritic synapses; these showed symmetrical or asymmetrical characteristics, suggesting a phenotypic diversity of KP afferents. Heterogeneity of afferents was also demonstrated by differential co-expression of neuropeptides; in OVX + E(2) mice, KP afferents to GnRH neurones showed galanin-immunoreactivity with an incidence of 22.50 ± 2.41% and NKB-immunoreactivity with an incidence of 5.61 ± 2.57%. In OVX + oil animals, galanin-immunoreactivity in the KP afferents showed a major reduction, appearing in only 5.78 ± 1.57%. Analysis for co-localisation of galanin or NKB with KP was extended to the perikaryal level in animal models, which showed the highest KP incidence; these were OVX + E(2) females for the RP3V and OVX + oil females for the ARC. In the RP3V of colchicine-treated OVX + E(2) animals, 87.84 ± 2.65% of KP-IR neurones were galanin positive. In the Arc of the colchicine-treated OVX + oil animals, galanin immunoreactivity was detected in only 12.50 ± 1.92% of the KP expressing neurones. By contrast, the incidence of co-localisation with NKB in the Arc of those animals was 98.09 ± 1.30%. In situ hybridisation histochemistry of sections from OVX + E(2) animals identified galanin message in more than a third of the KP neurones in the RP3V (38.67 ± 11.57%) and in the Arc (42.50 ± 12.52%). These data suggest that GnRH neurones are innervated by chemically heterogeneous KP cell populations, with a small proportion deriving from the Arc group. The presence of galanin within KP axons innervating GnRH neurones and the oestrogen-dependent regulation of that presence add a new dimension to the roles played by galanin in the central regulation of reproduction.

Estradiol down-regulates RF-amide-related peptide (RFRP) expression in the mouse hypothalamus

In most mammals, RF-amide-related peptides are synthesized in the dorsomedial hypothalamic nucleus and regulate reproduction via inhibiting GnRH neurons and, possibly, adenohypophyseal gonadotrophs. In the present study, we investigated the possibility that RFRP-synthesizing neurons are involved in estrogen feedback signaling to the reproductive axis in mice. First, we used quantitative in situ hybridization and compared the expression of prepro-RFRP mRNA of ovariectomized mice, with and without 17β-estradiol (E2) replacement. Subcutaneous administration of E2 via silastic capsules for 4 d significantly down-regulated prepro-RFRP mRNA expression. The underlying receptor mechanism was investigated with immunohistochemistry. In ovariectomized mice, low levels of nuclear estrogen receptor (ER)-α immunoreactivity were detectable in 18.7 ± 3.8% of RFRP neurons. The majority of RFRP neurons showed no ER-α signal, and RFRP neurons did not exhibit ER-β immunoreactivity. Results of these studies indicate that RFRP is a negatively estradiol-regulated neurotransmitter/neuromodulator in mice. The estrogenic down-regulation of RFRP expression may contribute to estrogen feedback to the reproductive axis. The issue of whether E2 regulates RFRP neurons directly or indirectly remains open given that ER-α immunoreactivity is present only at low levels in a subset of these cells.

Cerebrovascular reactivity and reserve capacity in type II diabetes mellitus

The aim of the study was to test the hypothesis that cerebrovascular reserve capacity and cerebrovascular reactivity are impaired in patients suffering from non insulin-dependent diabetes mellitus. We also intended to investigate factors which may influence resting cerebral blood flow velocity and cerebrovascular reserve capacity. A total of 28 patients suffering from type II diabetes mellitus and 20 healthy control subjects were studied. Based on diabetes duration patients were divided into two groups: subjects with > 10 years and those with < or = 10 years disease duration. Middle cerebral artery mean blood flow velocities were measured at rest and after intravenous administration of 1g acetazolamide. Cerebrovascular reactivity and reserve capacity were calculated. Blood glucose, insulin, glycosylated hemoglobin, hemostatic factors (fibrinogen, alpha-2 macroglobulin and von Willebrand factor antigen) were determined. Cerebrovascular reactivity and reserve capacity values were compared between the two diabetic subgroups and controls. Correlations between laboratory parameters and cerebrovascular reserve were investigated by linear regression analysis. Resting cerebral blood flow velocity was similar in controls and in the two diabetic subgroups. Cerebrovascular reactivity was elevated for a shorter time in patients with > 10 years disease duration than in controls and short-term diabetic patients. Cerebrovascular reserve capacity was lower in the long-term diabetes group (means +/- SD: 39.6 +/- 20.7%) than in patients with < or = 10 years disease duration (63.3 +/- 17.4%, p < 0.02 after Bonferroni correction). Cerebrovascular reserve capacity was inversely related to the duration of the disease (R = 0.53, p < 0.003). None of the determined laboratory factors had any relation with resting cerebral blood flow and cerebrovascular reserve capacity. The vasodilatory ability of cerebral arterioles is diminished in long-standing type II diabetes mellitus.

Synthesis and biological activity of a new progestogen, 16-methylene-17alpha-hydroxy-18-methyl-19-norpregn-4-ene-3, 20-dione acetate

The progestational activity of second- and third-generation progestins in oral contraceptives were markedly increased by addition of an 18-methyl group. A new progestin, the 18-methyl analog of Nestorone, 16-methylene-17alpha-hydroxy-18-methyl-19-norpregn-4-ene-3,2 0-dione acetate (10), was synthesized. The relative binding affinity and biologic activity of 10 was compared with Nestorone, levonorgestrel, and progesterone using a binding assay for rat progesterone receptors, the Clauberg assay in the rabbit, and by assessing pregnancy maintenance in the rat. These studies, as summarized in Table 4, show that 10 is three to ten times more potent than Nestorone. The addition of the 18-methyl group to Nestorone markedly increased its potency as noted above, but is unlikely to change its rate of delivery from sustained release systems. 10 should be ideally suited for administration by implants or small skin patches.

Effect of sevoflurane on cerebral blood flow and cerebrovascular resistance at surgical level of anaesthesia: a transcranial Doppler study

BACKGROUND AND OBJECTIVE

It is widely accepted that sevoflurane affects cerebral circulation, but there are uncertainities regarding the magnitude of its effect. The aim of the present work was to assess the effect of sevoflurane on the cerebral circulation at surgical levels of anaesthesia.

METHODS

Twenty patients undergoing elective lumbar discectomies were investigated. Anaesthesia was induced with propofol and maintained with sevoflurane. The level of surgical anaesthesia was determined by bispectral index, the target level was 45-55. Transcranial Doppler (TCD) measurement was performed before induction and after reaching the surgical level of anaesthesia. Besides routine parameters (middle cerebral artery mean blood flow velocity (MCAV) and pulsatility index (PI)) derived parameters (estimated cerebral perfusion pressure (eCPP), cerebral blood flow index (CBFI) and resistance area product (RAP)) were calculated by taking changes of mean arterial pressure also into account.

RESULTS

MCAV decreased from 54.1 +/- 13.3 to 43.7 +/- 18.5 cm s-1, P < 0.01 and PI increased from 0.79 +/- 0.2 to 0.92 +/- 0.2, P < 0.01 after reaching the surgical level of anaesthesia. As a result eCPP decreased by 18.2%, CBFI by 25.5% and RAP increased by 15% respectively.

CONCLUSIONS

Our data indicate a vasodilatory effect of sevoflurane at surgical level of anaesthesia on large cerebral vessels or a vasoconstriction of the resistance arterioles likely caused by decreased brain metabolism.

Effect of hyperventilation on cerebral blood flow velocity in preeclamptic pregnancies: is there evidence for an altered cerebral vasoreactivity?

The purpose of this study was to investigate cerebral arteriolar vasoreactivity function in preeclampsia. Preeclamptic (n = 26) and healthy pregnant (n = 22) women underwent transcranial Doppler sonography of the middle cerebral artery at rest and after 60 seconds of hyperventilation (HV). Systolic, diastolic, and mean blood flow velocities were recorded. The percentage change of the blood flow velocities after HV was calculated. Mean blood flow velocity of the middle cerebral artery was higher in preeclamptic women as compared with healthy pregnant women. No difference could be detected in percentage change of middle cerebral artery blood flow velocities after HV between the two groups. There is no evidence of a small-vessel vasoconstriction among preeclamptic patients. The role of vasoconstriction of the large cerebral arteries and vasodilation of the resistance arterioles, as well as a combination of these 2 pathomechanisms, in determining cerebral blood flow in preeclampsia and eclampsia should be investigated in further studies.

Description of patients with IgG4-related disease from a Hungarian centre

OBJECTIVES

Although most reported patients with immunoglobulin G4-related disease (IgG4-RD) are from the Far East, we aimed to identify patients suffering from IgG4-RD in our University Centre in Debrecen, Hungary.

METHOD

Serum IgG4 levels were measured at 51 of our 800 patients followed up because of Sjögren's syndrome (SS) if one or more clinical signs during the disease course raised the possibility of IgG4-RD (persisting salivary gland swelling, absence of anti-Ro/SSA and anti-La/SSB antibodies in the serum, and positive salivary gland biopsy, coexistence of autoimmune pancreatitis, autoimmune hepatitis, or primary sclerosing cholangitis, persisting lymphadenopathy). Where available, histological samples of small salivary gland biopsies were revised to detect the particular features of IgG4-RD. Pathologists and surgeons were informed about the disease and asked to refer suspicious cases.

RESULTS

Based on our survey, eight patients were identified with IgG4-RD. Pancreatic, salivary gland, aortic, and retroperitoneal manifestations were detected. Of the 51 patients with SS, four appeared to have IgG4-RD, but eventually one was excluded.

CONCLUSIONS

Although IgG4-RD is not yet well known to physicians of Western countries, it occurs in Caucasians and probably in other races as well. Moreover, our eight cases diagnosed with IgG4-RD demonstrate a relatively large European patient population collected in a single centre. European clinicians, and especially rheumatologists, should be informed and at least certain laboratories should be prepared to investigate patient samples if the suspicion of IgG4-RD is raised. The main clinical significance of an accurate diagnosis is the extreme corticosteroid sensitivity of IgG4-RD.

No relationship between cerebral blood flow velocity and cerebrovascular reserve capacity and contemporaneously measured glucose and insulin concentrations in diabetes mellitus

Blood glucose and insulin concentrations have been reported to influence cerebral hemodynamics. We studied the relationship between actual blood glucose and insulin concentrations and resting cerebral blood flow velocity in the middle cerebral artery and cerebrovascular reserve capacity after acetazolamide stimulation. Thirty-six insulin-dependent diabetic patients in a state of good glycemic control were studied. Blood samples were taken for determination of glucose and insulin concentrations. Subsequently we measured resting cerebral blood flow velocities in supine position using transcranial Doppler, administered 1 g acetazolamide intravenously, and repeated the measurements after 5, 10, 15 and 20 minutes. Cerebrovascular reserve was calculated as the maximal percent increase after acetazolamide stimulation. Multiple regression was used for statistical analysis. Blood glucose levels were not correlated with resting blood flow velocity (R = 0.21, p = 0.22) nor cerebrovascular reserve capacity (R = 0.17, p = 0.32). Similarly, no correlation was found between insulin concentrations, resting cerebral blood flow velocity (R = 0.24, p = 0.22) and cerebrovascular reserve (R = 0.26, p = 0.24). Studying patients with long-term (> 10 years) and short-term (</= 10 years) disease duration yielded the same lack of correlation. We conclude that there is no significant correlation between contemporaneously measured glucose and insulin concentrations and either cerebral blood flow velocity or cerebrovascular reserve capacity in the middle cerebral artery in type 1 diabetic patients with good control.

Cannabinoid modulation of midbrain urocortin 1 neurones during acute and chronic stress

Neurones in the centrally projecting Edinger-Westphal nucleus (EWcp) are the main site of urocortin 1 (Ucn1) synthesis in the mammalian brain, and are assumed to play a role in the stress response of the animal. Because endocannabinoid signalling has also been strongly implicated in stress, we hypothesised that endocannabinoids may modulate the functioning of the urocortinergic EWcp. First, using in situ hybridisation, we demonstrated cannabinoid receptor 1 (CB1R) mRNA expression in mouse EWcp-neurones that were Ucn1-negative. Dual- and triple-label immunocytochemistry revealed the presence of CB1R in several GABA-immunopositive fibres juxtaposed to EWcp-Ucn1 neurones. To test functional aspects of such an anatomical constellation, we compared acute (1 h of restraint) and chronic (14 days of chronic mild stress) stress-induced changes in wild-type (WT) and CB1R knockout (CB1R-KO) mice. Acute and especially chronic stress resulted in an increase in Ucn1 content of the EWcp, which was attenuated in CB1R-KO mice. CB1R-KO mice had higher basal and chronic stress-induced adrenocorticotrophin and corticosterone levels and were more anxious on the elevated plus-maze versus WT. Collectively, our results show for the first time EWcp-Ucn1 neurones are putatively innervated by endocannabinoid sensitive, inhibitory, GABAergic afferents. In addition, we provide novel evidence that the absence of the CB1 receptor alters the Ucn1 mRNA and peptide levels in EWcp neurones, concomitant with an augmented stress response and increased anxiety-like behaviour.

Assessment of cerebral hemodynamics during roll over test in healthy pregnant women and those with pre-eclampsia

OBJECTIVE

To compare cerebral autoregulatory responses obtained during roll over tests in healthy pregnant women and those with pre-eclampsia in order to assess the middle cerebral artery velocity changes in relation to the roll over test in normotensive and pre-eclamptic women.

PARTICIPANTS

Twenty-two healthy pregnant women and 26 with pre-eclampsia underwent transcranial Doppler measurements of the middle cerebral artery.

METHODS

Systolic, mean and diastolic blood flow velocities and mean arterial blood pressures were recorded in the left lateral position and five minutes after turning to the supine position. Absolute values of mean blood flow velocities, mean arterial blood pressure values and calculated cerebral blood flow indices as well as cerebrovascular resistance area products were compared at different positions among the groups.

RESULTS

Mean arterial blood pressure increased in both groups while turning from the left lateral to the supine position. In women with pre-eclampsia both mean arterial blood pressure and absolute values of mean blood flow velocity values were higher in both positions, compared with healthy pregnant women. In both groups, changing the position resulted in a decrease of absolute values of mean blood flow velocities. Calculated cerebral blood flow indices did not change, while cerebrovascular resistance area products increased significantly in the groups during roll over testing. In women with pre-eclampsia, the increase of cerebrovascular resistance area products was more pronounced as compared with healthy pregnant women.

CONCLUSIONS

In women with pre-eclampsia roll over test results in an increase of the mean arterial blood pressure, which is accompanied by a decreased mean blood flow velocity in the middle cerebral artery. Further studies are needed to clarify the pathophysiological background of cerebral haemodynamic changes in pre-eclampsia.

Transtracheal electrical stimulation of the spinal cord for intraoperative monitoring of the motor pathway

Because of the suppressant effects of anesthetic drugs and muscle relaxants on motor responses elicited by either magnetic or electrical transcranial stimulation, intraoperative monitoring of the motor system, and especially monitoring of lower limb function, presents many difficulties. The upper part of the spinal cord was stimulated in 14 anesthetized and relaxed dogs with a cathode attached to the intratracheal tube and an anode fixed above the upper cervical spinous processes. Action potentials evoked by single and serial stimuli were recorded from the exposed right femoral nerve and quadriceps muscle Averaging was necessary for serial stimulations. Reproducible early and late responses to both single and serial stimulations were recorded during regular anesthesia. The origin of the different responses is discussed. Transtracheal stimulation of the spinal cord is easy to perform and the responses recorded from the peripheral nerve or limb muscle are well reproducible in regular anesthesia. The method seems to be appropriate for intraoperative monitoring of the thoracolumbar spine.

[Cerebrovascular reactivity in non-insulin dependent diabetes mellitus (preliminary results)]

AIMS

Previously numerous investigators reported about impairment of cerebrovascular reserve capacity in Type I, diabetes mellitus. However, no similar data are available about patients suffering from Type II diabetes. The goal of the study was to assess cerebrovascular reserve in Type II diabetic patients.

PATIENTS AND METHODS

14 NIDDM patients and 20 healthy controls were studied. Middle cerebral artery mean blood flow velocity was measured at rest and during 20 minutes after i.v. administration of 1 g. acetazolamide. Velocities measured after acetazolamide were compared to resting values and were expressed as the percent increase of the mean velocity. Data obtained in diabetics and healthy persons were compared using Student's t-test. The correlation between age of the patients, diabetes duration, actual blood glucose-, insulin-, glycosylated hemoglobin-, urine microalbumin concentrations and resting blood flow velocity and cerebrovascular reserve capacity was assessed using linear regression analysis.

RESULTS

Resting cerebral blood flow velocities, cerebrovascular reactivity and reserve capacity did not differ from that of healthy controls. No correlation has been found between obtained laboratory parameters and resting cerebral blood flow velocities and cerebrovascular reserve capacity.

CONCLUSIONS

Vasodilatory ability of the cerebral arterioles in NIDDM-patients did not differ from that of healthy control persons. Further studies are needed to find out an accurate screening method for detection of cerebral microangiopathic changes in Type II diabetes mellitus.

[Study of the virulence of coagulase-negative staphylococci in experimental infections]

The pathogenicity and virulence of 3 strains of Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus saprophyticus, respectively were studied in BALB/c mice by intraperitoneal (ip) challenge using 4 bacterial suspensions of different colony forming units (CFU) of each strain. Strains were isolated from wound, blood, and urine of inpatients. On the base of the lethality rates, S. saprophyticus proved to be the most virulent (LD50 = 2.7-2.9 x 10(7) CFU/g body wt), while the S. epidermidis species was the least virulent (LD50 = 6-8 x 10(7) CFU/g body wt). The lethality rate of male mice was higher than that of the female ones at the same challenge bacterium concentration. Mice of higher body weight were generally more sensitive to a quality of bacteria calculated to 1 g of mice than the lighter mice. The 245 mice surviving the challenge were dissected at the 10th day of infection. Splenomegaly was found to be the most frequent macroscopic pathological alteration. There appeared kidney abscesses, liver abscesses, and rarely peritoneal abscess. The frequency of pathological findings were directly proportional to the amount of bacteria injected. The results indicate that clinical strains of coagulase-negative staphylococci (CNS) examined were pathogenic and virulent for BALB/c mice they are invasive after ip injection and can cause macroscopic pathological changes in parenchymal organs. Thus, ip CNS challenge in mice may be a model to imitate and study infections caused by CNS in human.

[Importance of cerebrovascular reactivity testing in diabetes mellitus]

Diabetes mellitus results in macro- and microangiopathies. Early diagnosis and preventive treatment of the cerebral vessel complications may influence the prognosis of the disease. The aim of the present work is to summarize the recent results of the cerebral hemodynamic studies in diabetics. A suitable, non-invasive screening method for diagnosis of the altered cerebral arteriolar function is discussed.

[Necrosis of the galea as rare complication of infection of a traumatic temporal hematoma]

Authors report a case of infective traumatic temporal haematoma causing septic focus. The suppurative inflammation developed two weeks after the trauma causing necrosis of an extensive part of the galea on a big area of the crown of head. A septic process increased producing necrotic alteration of the affected periosteum of the cranial bone and plegmon in the tissue of the neck. Authors report the surgical plastic procedures that were used to establish a granulating layer and to cover the surface in the area of the removed necrotic part of the galea. Authors emphasize the significance of the danger of the inflammatory infiltration and report the effect of the Curiosin solution on the wound-healing.

Intraoperative monitoring of the motor pathway using transtracheal stimulation of the cervical spine in dogs

Although SEP monitoring of the spinal cord has been a well established method recently, not an ultimate, perfectly developed technique for monitoring of the motor system is known so far, particularly, because of the disturbing effect of narcotic drugs and relaxants on the motor evoked potentials. In this study the upper part of the spinal cord was stimulated in 14 anesthetized and relaxed dogs with a cathode attached to the intratracheal tube and an anode fixed to the cervical spinous processes. Single and serial stimuli were applied. Recordings were obtained from the exposed right femoral nerve and quadriceps muscle. Averaging was necessary when using serial stimulations. Responses were consequent and reproducible during regular anesthesia. The origin of the different responses in the spinal cord is discussed. The method seems to be appropriate for intraoperative monitoring of the thoracolumbar spine.

[Pathogenic properties of coagulase-negative staphylococci in experimental infections]

The frequency of persistence of three Staphylococcus epidermidis, Staphylococcus haemolyticus and Staphylococcus saprophyticus strains, respectively, was studied in BALB/c mice at the 10th day of intraperitoneal (ip) challenge. 245 out of 416 mice survived after infections with four bacterial suspensions of different colony forming units (CFU) of each strain. Staphylococci persisted in 61 mice (24,9%). The main sites of persistence were the kidneys, while cocci were rarely isolated from the spleen and the liver. S. epidermidis persisted with a significantly higher rate than the other two species, because S. epidermidis in 28,8%, S. haemolyticus in 4,9%, and S. saprophyticus in 3,6% were reisolated from the organs of the respective infected and surviving animals. The organ persistence was proportional to the amount of bacteria injected. The persistence resulted in subacute microabscesses in the organs. Reisolates of persisting bacteria remained stable in phenotype and genotype concerning antibiotic resistance patterns and biochemical activities for the taxonomic implication, whereas cell surface properties characterizable with phage types altered considerably during persistence. It is concluded that cocci of all three Staphylococcus species are invasive and can persist to a certain extent in the organs of animals with normal immune system, too, after artificial inoculation into the peritoneum i. e. to the serosal surfaces.

[Clinical importance of assessment of collateral capacity in the circle of Willis. Benefit of a mathematical blood flow model for the every-day practice of vascular surgery]

Collateral capacity of the Willisian arteries is of clinical importance during and after carotid endarterectomies.

AIMS

Assessment of cerebral hemodynamics using a flow circulation model based on a mathematical formula.

PATIENTS AND METHODS

Four patients suffering from ischemic stroke in moribund stage were investigated using transcranial color-coded duplex sonography. By compressing the common carotid arteries, the function of the Willisian collaterals was assessed. After the death of the patients, the circles were removed, the diameters and lengths of the arterial segments were measured. The data were analysed with the mentioned circulation model.

RESULTS

The diameters of non-functioning collateral arteries were 0.4 mm, while that of the functional ones were 0.7 and 0.8 mm, respectively. In the two cases where the anterior communicating arteries did not function, a near-critical hemodynamical status was found in the end-arteries. This was especially true if the mean arterial blood pressure was 70 mmHg. The most critical hemodynamical status developed in case 4, where internal carotid occlusion on one side, a contralateral severe carotid stenosis and a non-functioning anterior communicating artery were observed.

CONCLUSIONS

A special flow circulation model based on mathematical formula enables the calculation of the cerebral blood flow in the different arterial segments of the circle of Willis. Further studies are needed to clarify whether the method can be used for preoperative modeling of the cross-clamping phase of carotid endarterectomy.

[Cerebrovascular reactivity in insulin dependent diabetes mellitus studied by an acetazolamide test]

The aim of this study was to investigate, whether the cerebrovascular reactivity (CR) was altered in diabetes mellitus and to evaluate the influence of diabetes's duration on cerebrovascular reactivity. Transcranial Doppler-Acetazolamide tests were performed on 20 insulin-dependent diabetics and in 19 controls. Patients were divided into two groups, each group consisted of 10 patients: diabetics with > 10 years disease duration and with < 10 years diseases duration. Middle cerebral artery mean velocities were measured at rest and after i.v. administration of Ig Acetazolamide (AZ). There were no differences in the absolute velocities between controls and diabetics. The percentual increase of the mean velocity after AZ was slower and less intensive in longterm diabetics (means +/- SE: 5 min: 19.4 +/- 2.8%, 10 min: 28 +/- 3.6%, 15 min: 25.7 +/- 3.8%, 20 min: 23.9 +/- 4.3%), than that in controls (5 min: 32.3 +/- 4.3% -p < 0.05-, 10 min: 45.1 +/- 4.9% -p < 0.05-, 15 min: 47.5 +/- 4.3% -p < 0.01-, 20 min: 46.5 +/- 4.7% -p < 0.01) as well as in diabetics with < 10 years disease duration (5 min.: 39.5 +/- 7% -p < 0.05-, 10 min.: 49.2 +/- 6.5% -p < 0.05-, 15 min.: 53.9 +/- 8.6% -p < 0.01-, 20 min: 32.9 +/- 5.9% -n.s.). The cerebrovascular reactivity is impaired in diabetics after long duration of the disease. The altered cerebrovascular reactivity might be caused by angiopathy of the cerebral arterioles.