An evaluation of the biological significance of aluminium in plasma and hair of patients on long-term hemodialysis

In hemodialyzed patients, the risk of toxicity attributed to the body accumulation of aluminium (Al) justifies the need for monitoring Al in various human media. In this study, Al concentrations in the hair and plasma of 78 hemodialyzed patients with chronic renal failure and of 351 healthy volunteers were measured by electrothermal atomic absorption spectrometry with Zeeman effect. Plasma Al concentrations in patients were significantly higher than in the controls and positively correlated with time on dialysis. Hair Al levels were widely distributed with no significant distinction between patients and controls. On the subject of establishing correlation, the authors stress the importance of taking into account the kinetics of the elimination of minerals from hair. Even when this was done, in the patient group there was no statistical link between plasma and hair Al levels. Hair Al analysis is of no value as an indicator of body Al accumulation.

Evidence of lipoperoxidation induced by lactic acid on kidney homogenates

Sawas and Gilbert (Arch. Int. Pharmacodyn. Ther., 276 (1985) 301-312) reported that the commercial solution of haloperidol induces lipoperoxidation of kidney homogenates from Sprague-Dawley rats. However, it would appear that this effect is attributable to the excipient, lactic acid, rather than to haloperidol itself. Lactic acid enhances susceptibility to lipoperoxidation of kidney homogenates in a dose- and time-dependent manner by increasing production of thiobarbituric acid-reactive substances and slightly decreasing polyunsaturated fatty acids such as arachidonic acid and docosahexaenoic acid. This stimulation of lipoperoxidation may be attributed to a mechanism less dependent on enzymatic action than on Fe2+ and Fe3+. Lactic acid may facilitate iron release and formation of iron complexes, factors which increase susceptibility to oxidative stress.

Risk factors for cytomegalovirus infection in BMT recipients transfused exclusively with seronegative blood products

Risk factors for developing cytomegalovirus (CMV) infection and pneumonitis were analysed in 100 unselected consecutive patients undergoing allogenic BMT. This series is homogeneous because of the same diagnostic procedures, BMT technique and supportive care (exclusive seronegative blood products, no CMV immunoglobulin, no prophylactic antiviral). The incidence of CMV infection and CMV interstitial pneumonitis (CMV-IP) were 44% and 13% respectively, of whom five patients died. Variables such as age, sex, underlying disease, conditioning regimen and occurrence of GVHD were not found as significant risk factors. We confirm that the only major factor was recipient's serology as CMV infection and IP occurred in 4% and 0% respectively among negative recipients (R-) compared with 79% and 25% among positive R. In contrast to some studies among R+, neither donor's immunity nor recipient's CMV humoral response improved the clinical outcome. This study validates the good predictive value of viremia and urinary virus excretion for the occurrence of CMV-IP (respectively positive in 11 and 13 patients out of 13 with IP), always preceding IP by a median of 37 and 27 days. The highest risk patients for lethal CMV-IP were older recipients (> 30 years). Thus, prospective prophylactic trials with antiviral agents are suggested in such viremic or viruric patients. Furthermore, the use of seronegative blood products is highly effective and sufficient to prevent CMV infection in R-patients.

Autologous stem cell transplantation versus chemotherapy for adult patients with acute myeloid leukemia in first remission: the BGMT Group experience

The BGMT 87 study was designed to compare prospectively Allogeneic Bone Marrow Transplantation (AlloBMT), Autologous Stem Cell Transplantation (ASCT) and Chemotherapy (CT). Of the patients who could not undergo AlloBMT and were still in remission after two cycles of intensive CT were randomized for ASCT (n = 39) or CT (n = 38). The actuarial risk of relapse was 48.7 +/- 8.8% (95% ci) in the ASCT group and 61.1 +/- 8.4% (95% ci) in the CT group (p = NS). The estimated chance of surviving without disease at three years was similar in both groups (48.3 +/- 8.5% versus 38.9 +/- 8.4; p = NS).

Absence of a direct coupling of a G protein to dihydropyridine binding sites in rat heart

In rat heart membranes, the addition of guanine 5'-O-(3-thiotriphosphate) (GTP-gamma-S), a stable GTP analogue, did not significantly modify the displacement of [3H]PN 200-110 binding by the 1,4-dihydropyridine (DHP) agonist Bay K 8644 and antagonists, nifedipine and nicardipine. These results are in agreement with some previously reported electrophysiological and pharmacological data, and they suggest that there is no direct involvement of a G protein in the modulation of DHP sensitive Ca channels in cardiac cells.

t(9;11)(p22;q23) translocation in blastic phase of chronic myeloid leukemia

A patient with chronic myeloid leukemia showed clonal karyotypic evolution, with the appearance of an i(17q) and t(9;11)(p22;q23). This case sheds light upon leukemogenic events related to t(9;11)(p22;q23). The presence of t(9;22) and t(9;11) in the same clone showed that t(9;11) may affect a pluripotent stem cell, thus accounting for t(9;11) in both lymphoid and monocytic leukemias. In this patient, t(9;11) could not be related to a prior cytotoxic exposure and was instead the result of natural evolution of chronic myeloid leukemia. Furthermore, this led us to assume that the phenotype of blast cells may be determined by a chromosome abnormality. A phenotypic conversion from myeloblastic to undifferentiated morphologic aspect was observed when t(9;11) was detected, suggesting that t(9;11) may have induced a loss in differentiation of blast cells affected by this change. This assumption is in agreement with the putative presence of genes activated in pluripotent progenitors by 11q23 rearrangements.

Alpha 2-adrenoceptor changes during cerebral ageing. The effect of Ginkgo biloba extract

[3H]Rauwolscine binding to alpha 2-adrenoceptors in cerebral cortex and hippocampus membranes of young (4 months) and aged (24 months) Wistar rats has been investigated. In aged rats, Bmax values of [3H]rauwolscine binding were significantly reduced (25-32%) in the cerebral cortex and hippocampus, as compared with the number of alpha 2-adrenoceptors found in young rats. Chronic treatment with Ginkgo biloba extract did not alter [3H]rauwolscine binding in the hippocampus of young rats, but significantly increased (28%) the [3H]rauwolscine binding density in aged rats. These data confirm the previously described age-related noradrenergic alteration and suggest that noradrenergic activity in aged rats is more susceptible to Ginkgo biloba extract treatment.

Prevention of hepatic veno-occlusive disease after bone marrow transplantation by continuous infusion of low-dose heparin: a prospective, randomized trial

Hepatic veno-occlusive disease (VOD) is a major regimen-related toxicity after bone marrow transplantation (BMT). Endothelial injury, leading to deposition of coagulation factors within the terminal hepatic venules, is believed to be the key event in the pathogenesis of VOD. To evaluate the benefit and the safety of a VOD prophylaxis with anticoagulants, we conducted a prospective randomized trial of continuous infusion of low-dose heparin among 161 patients under-going either allogeneic (n = 79) or autologous BMT (n = 81). Patients were randomized to receive (n = 81) or not receive (n = 80) prophylactic heparin 100 U/kg/d by continuous infusion from day -8 until day +30 post-BMT. Heparin was found to be highly effective in preventing VOD, which occurred in 11 of 80 patients (13.7%) in the control group versus 2 of 81 (2.5%) in the heparin group (P less than .01). Furthermore, none of the 39 patients in the heparin group developed VOD after allogeneic BMT, versus 7 of 38 (18.4%) in the control group (P less than .01). This prophylactic effect was achieved without added risk of bleeding. Indeed, the low-dose heparin we used did not prolong the partial thromboplastin time and did not increase the red blood cell and platelet requirements. It is therefore recommended that heparin prophylaxis be part of early mortality prevention programs after BMT.

Intensive combined therapy for previously untreated aggressive myeloma

A trial was initiated to determine the feasibility and efficacy of a three-phase treatment including: (1) induction chemotherapy (IC); (2) high-dose melphalan with total body irradiation supported by unpurged autologous bone marrow transplantation (ABMT); and (3) interferon (IFN) alpha maintenance treatment, in previously untreated aggressive myeloma. Thirty-five consecutive patients, ages under 65 years, were enrolled. Initial induction therapy was randomized between the VAD regimen (vincristine, doxorubicin, dexamethasone) or the VMCP regimen (vincristine, melphalan, cyclophosphamide, prednisone) that were found to give similar results as IC. Thirty-one of 35 (89%) patients, with good performance status and normal renal function after IC, received ABMT. IFN alpha was started soon after ABMT and was well tolerated. Fifteen of 35 (43%) patients achieved complete response (CR) and 14 of 35 (40%) achieved partial response (PR). Low pretreatment beta 2 microglobulin was the only predictive factor for accomplishing CR. The duration of response was significantly affected by the magnitude of response. The 33-month, post-ABMT probability of progression-free survival was 85% for patients in CR versus 24% for patients in PR. The 42-month, post-diagnosis probability of survival was 81%. This overall strategy may represent an advance in the management of multiple myeloma. Furthermore, the high rate and long duration of CR that we observed in patients with low beta 2 microglobulin suggest that such patients may preferentially benefit from this strategy.

Maintenance treatment with recombinant alpha interferon after autologous bone marrow transplantation for aggressive myeloma in first remission after conventional induction chemotherapy

Twenty patients (median age 57 years) with high tumor mass myeloma in first remission after conventional chemotherapy received a two-phase treatment: autologous bone marrow transplantation (ABMT) using a preparative regimen of high dose melphalan plus total body irradiation followed by maintenance treatment with recombinant alpha interferon. Before ABMT all patients were in partial remission, while after ABMT 10 (50%) achieved complete remission, and 10 remained in partial remission (with a 90% decrease in measurable paraprotein in 7/10). With a median follow-up of 19.8 months (12.2-33.5) after diagnosis and 13 months (4-25) after ABMT, the Kaplan-Meier 2-year post-ABMT probability of progression-free survival was 85% (95% CI = 58.7-95.8%). None of the 10 patients in complete remission has relapsed. No toxic death occurred. Alpha interferon was introduced early after ABMT (2.7 months) and was well tolerated. This strategy may represent an advance in the management of aggressive myeloma.

Phase I/II pharmacokinetic study of mitoxantrone by continuous venous infusion in patients with solid tumours and lymphoproliferative diseases

Phase I and pharmacokinetic studies were performed in order to evaluate the maximum tolerated dose and the efficiency of 120 h continuous venous infusion (CVI) of mitoxantrone. 25 patients suffering from either metastatic solid tumour or refractory lymphoproliferative disease were included in the study. The starting dose was 2 mg/m2 per day and was increased by a 0.2 mg/m2 per day step dose. The main toxicity observed was leukopenia which became limiting in more than 50% of the patients receiving 2.4 mg/m2 per day (12 mg/m2 over a 120 h period); this dose was defined as the maximal tolerated dose in these pretreated patients. One partial response and three stable diseases were observed. A plasma plateau concentration of mitoxantrone (2.13 [S.D. 0.54] micrograms/1 at 2 mg/m2 per day, 2.56 [1.32] micrograms/1 at 2.2 per day and 3.46 [1.32] micrograms/l at 2.4 mg/m2 per day) was reached within 24-48 h. It was linearly related to the administered dose. The mean plasma clearance of mitoxantrone was 27.8 [14.2] l/h/m2 and the volume of distribution of the beta phase averaged 2327 [2125] l/m2. An inverse relationship was established between the mitoxantrone clearance and the degree of hematologic toxicity. This 120 h CVI mitoxantrone schedule was safe and could be repeated every 3 weeks in an outpatient setting. The relationship between mitoxantrone clearance and the drug related haematotoxicity could be used for an individual dose adjustment.

Prevention of gram-positive infections after bone marrow transplantation by systemic vancomycin: a prospective, randomized trial

Gram-positive bacteria are the most commonly isolated organisms after bone marrow transplantation (BMT) and severe streptococcus septicemia has been reported. In order to evaluate the benefit of a gram-positive prophylaxis after BMT, we conducted a prospective, randomized trial of systemic vancomycin among 60 patients undergoing BMT for hematologic malignancies. Patients were randomized to receive (n = 30) or not receive (n = 30) prophylactic vancomycin 15 mg/kg every 12 hours from day -2 until resolution of neutropenia or until the first episode of fever. All patients were treated in laminar air-flow rooms, received sterile diet, total gut decontamination, and had central venous catheters placed surgically. Vancomycin was found to be highly effective in preventing gram-positive infections that occurred in 11 of 30 patients in the control group versus zero of 30 in the vancomycin group (P less than .002). All gram-positive infections occurring in the control group were symptomatic (nine septicemia and two local infections), and one patient with Streptococcus septicemia died with pneumonia. Thus, gram-positive prophylaxis was found to decrease infection morbidity after BMT. Moreover, the number of days with fever (P less than .001), and empiric antibiotic therapy (P less than .01) was reduced without added toxicity or cost. This study confirmed the high prevalence of gram-positive infections after BMT and emphasized the clinical benefits of an adapted prophylaxis.

Central 5HT1A-receptor binding in normotensive and spontaneously hypertensive rats

Central 5HT1A-receptors have been found with a high density in brainstem and are involved in cardiovascular control. The high-affinity binding of [3H]-8-OH-DPAT, a specific 5HT1A-receptor ligand, was measured in medulla oblongata of normotensive and spontaneously hypertensive rats (SHR). The maximal number of [3H]-8-OH-DPAT binding site (Bmax) was significantly increased in SHR when compared to normotensive rats. Whether central 5HT1A-receptors are involved in the etiology of hypertension or are influenced by other neurochemical events remains to be investigated.

Spiperone: a receptor ligand and/or a granular uptake tracer?

The accumulation of [3H]spiperone and [3H]dopamine was measured in striatum and pituitary gland slices of rat. Contrary to [3H]dopamine, [3H]spiperone storage was similar in striatum and pituitary gland. In addition, [3H]spiperone accumulation was not diminished by reserpine and tetrabenazine. These data show that spiperone is not subject to the granular uptake/storage mechanism and suggest that spiperone and its derivatives are specific ligands for dopamine receptors only.

Effect of hypertension and age on alpha 1-adrenoceptors in rat brain: modulation of [3H] prazosin binding by chronic treatment with desipramine and AR-C239

The influence of repeated treatment with desipramine or AR-C239 on cerebral cortex alpha 1-adrenoceptors of mature (4 months), senescent (24 months) Wistar-Kyoto and mature spontaneously hypertensive rats was measured using [3H] prazosin as a ligand. Chronic desipramine treatment had no effect on [3H] prazosin binding in mature and aged Wistar-Kyoto rats but significantly decreased it in spontaneously hypertensive rats. Repeated AR-C239 treatment did not alter [3H] prazosin binding in senescent Wistar-Kyoto and mature spontaneously hypertensive rats, but significantly increased the [3H] prazosin binding density in mature Wistar-Kyoto rats. Thus, cortical alpha 1-adrenoceptors are not up-regulated by a decreased noradrenergic activity in aged or hypertensive rats as is the case in mature normotensive rats. In addition, these receptors are down-regulated by an increased noradrenergic activity in hypertensive rats only. These results suggest that the synthesis of alpha 1-adrenoceptors is impaired with age or with genetic hypertension and their degeneration is exacerbated with genetic hypertension in response to a changing environment.

Iodobenzamide for in vivo exploration of central dopamine receptors: evaluation in animal models of supersensitivity

Iodobenzamide is a promising agent to investigate D2 receptors by SPECT in living human brain. In this work, we have evaluated this radiolabeled compound in two animal models of D2 receptors supersensitivity. In the first model, rats were treated chronically with haloperidol during three weeks (S.C. injection of 0.5 mg/kg/day). One week after the last day of treatment, they were I.V. injected with 125I-IBZM. In vivo specific binding study showed a 45 percent increase of 125I-IBZM fixation in the striatum of treated rats. In a second step of experiments, animals were unilaterally lesioned by a stereotaxic injection of 6-OHDA in the substantia nigra, 23 days before receiving 125I-IBZM. Autoradiographic analysis of coronal brain sections showed a 38 percent enhancement of 125I-IBZM in vivo binding in the striatum on the lesioned side as compared to the contralateral intact side; this increase occurred in striatal lateral area. These data demonstrate that 125I-IBZM is convenient to detect alterations of dopamine D2 receptors in vivo in the rat. Thus IBZM labelled with 123I can be a very useful imaging agent for the exploration of D2 receptors in pathological situations.

[125I]MIBG uptake and release in different regions of the rat brain

Radioiodinated m-iodobenzylguanidine [( 125I]MIBG) and tritiated norepinephrine [( 3H]NE]) uptake and release were compared, in different regions of the brain of the rat. The classification of the regions according to uptake was the same for both tracers:striatum greater than hypothalamus greater than hippocampus greater than cortex greater than brainstem. Tetrabenazine (TBZ), a granular monoamine uptake inhibitor reduced the uptake in the different regions. The inhibition rate was higher for [3H]NE uptake than for [125I]MIBG. The spontaneous release was the same for [125I]MIBG and [3H]NE and was the lowest in the striatum. The K+ stimulated release of [3H]NE was more complete than the release of [125I]MIBG and was the most important in the striatum. From these results, it is inferred that MIBG enters the brain tissue via NE uptake mechanisms. It appears that MIBG is stored in the chromaffin granules, as NE, but also in the cytoplasm. A modified molecule derived from MIBG which would cross the blood-brain barrier, would then appear as a potential scintigraphic marker of monoamine uptake, storage and release.

Central neurochemical effects of dihydropyridine calcium antagonists

Recent advances in central dihydropyridine (DHP)-binding sites are reviewed. DHP-binding sites are pre-synaptically and post-synaptically localized in the brain. The functional role of post-synaptic sites is still unknown, whereas pre-synaptic sites seem to contribute to the control of calcium uptake and of neurotransmitter release. DHP-binding sites may be modualated in physiological (age, sex) and pathological events (hypertension, ischaemia, neurological diseases) or after drug treatments (alcohol, morphine, etc.). The reviewed data suggest new therapeutic implications of DHP calcium channel antagonists in the treatment of other diseases and of drug withdrawal syndrome.

Central cardiovascular effects of dihydropyridines in spontaneously hypertensive rats

Intracerebroventricular (i.c.v.) injections of dihydropyridine derivatives calcium channel agonist (BAY K8644) and antagonist (nifedipine, nicardipine, PN 200-110) induced opposite long-lasting changes in blood pressure (BP) in pentobarbital anesthetized spontaneously hypertensive rats (SMR). I.c.v. nifedipine (NIF), nicardipine (NIC), and PN 200-110 decreased mean blood pressure dose-dependently and stereoselectively, (+) NIC and (+) PN being 8 and 3 times more potent than their (-) isomers, respectively. The decrease in BP was due to a withdrawal of the sympathetic tone, since NIF- and NIC-induced falls in BP were suppressed after either hexamethonium (HXM), 6 OHDA or bilateral adrenalectomy. I.c.v. BAY K8644 increased BP dose-dependently. The i.c.v. BAY K8644-induced hypertensive effect was inhibited: a), by NIF and (+) PN but not by (-) PN, therefore probably occurring at central DHP sites; b), by HXM and reserpine, thus probably mediated by an increase in sympathetic tone; c) by i.c.v. methylatropine (MA) while i.v. MA and i.c.v. HXM had no inhibitory effect, thus probably involving central muscarinic sites. In SHR, NIC did not after the K(+)-evoked ACh release but suppressed the BAY K8644-induced increase in ACh release. In anesthetized normotensive control rats (WKY), neither i.c.v. NIF, NIC or BAY increased BP and HR while, in conscious SHR it decreased BP without any change in HR. These data increased BP and HR while, in conscious SHR it decreased BP without any change in HR. These data suggest that central DHP sites may be involved in the cholinergic transmission and may participate in genetic hypertension via sympathetic tone.

[Effects of cicletanine on kidney lesions associated with age. Light and electron microscopy studies]

Aging laboratory animals constantly present with chronic progressive nephrosis. The purpose of this study was to investigate the protective effect of a chronic treatment with cicletanine in aging rats, notably as regards kidneys. Sixteen Wistar rats aged 26 months were divided into two groups: one group served as control, while the other received oral cicletanine 30 mg/kg/day. Blood pressure, weight and death rate were recorded. No rise of arterial pressure was observed in either group. The rats were killed on day 151, i.e. aged 31 months, after 5 months of treatment. All were autopsied and their kidneys, heart, lungs, liver, brain and eyes were removed for examination. Light microscopy of the renal tissue showed the lesions described in the chronic progressive nephrosis of the aging rat. These lesions were diffuse and pronounced in the control group and minimal in treated rats. The difference was confirmed by electron microscopy. The basal membrane of renal tubules was slightly thickened in the treated rats and two or three times thicker in control rats. Mitochondrial alterations were observed in the proximal tubules of controls but not in those of rats treated with cicletanine. Thus, after a 5-months treatment with cicletanine aging Wistar rats well known for their renal pathology were protected against kidney lesions in contrast with untreated rats.

The effect of cicletanine on cerebrovascular injury in stroke-prone spontaneously hypertensive rats

The stroke-prone spontaneously hypertensive rat (SHR-SP) is one of the most suitable models for stroke study. The present trial work was undertaken so as to obtain further information concerning the action of a new furopyridine, cicletanine. Forty-six males--SHR-SP/Iffa Credo rats--aged 7 weeks, were divided into three groups. Group 1 was a control group, groups 2 and 3 were orally treated with cicletanine at 30 and 100 mg/kg. Their drinking water contained 1% NaCl. Systolic blood pressure, body weight, and survival were recorded. After 6 weeks, all the rats were sacrificed. Samples of heart, brain, and kidney were fixed for light and ultrastructural examination. We found that cicletanine treatment (30 and 100 mg/kg) had significantly inhibited the incidence of hypertensive cerebral damages as characterized by cerebral infarction and vascular alterations with fibrinoid necrosis. Compared with the control group, the rats treated with the cicletanine had a significantly increased survival rate (P less than .001); the cicletanine also had an important protective effect on tissue. Cicletanine administration prevented the development of hypertensive cerebral vascular damage, probably through direct action on the vascular walls.

Sensitivity of fresh leukemic cells to T101 ricin A-chain immunotoxin: a comparative study between Fab fragment and whole Ig conjugates

We compared the cell killing potency of a whole Ig ricin A-chain immunotoxin (T101 IgG-RTA) against its Fab fragment counterpart (T101 Fab-RTA) on both CEM cells and fresh malignant lymphoid cells. A dye exclusion assay (DEA), was used to evaluate the kinetics of leukaemia cell viability mediated in vitro by each immunotoxin (IT). This study found that in the absence of ammonium chloride (NH4Cl), used as an enhancer agent, T101 Fab-RTA was significantly more toxic to both CEM and fresh leukaemia cells than T101 IgG-RTA. In the presence of NH4Cl (10(-2) M), while no differences could be found between the two IT on CEM cells, T101 Fab-RTA was clearly superior to T101 IgG-RTA on fresh leukaemia cells. These results suggest that T101 Fab-RTA may offer an excellent alternative to T101 IgG-RTA for IT treatment of CD5 positive leukaemia patients.

Comparison of MIBG and monoamines uptake mechanisms: pharmacological animal and blood platelets studies

The uptake of MIBG, a scintigraphic agent widely used in the detection of APUD tumours, was studied with a pharmacological approach on an in vitro and an in vivo models. MIBG as well as norepinephrine (NE) was taken up by human blood platelets, a model for presynaptic nerve endings amine uptake, with a thermodependant mechanism. MIBG and NE uptake was inhibited by desimipramine and reserpine. However, MIBG but not NE uptake was inhibited by fluvoxamine, a serotonin (5HT) uptake inhibitor. This suggests that MIBG is a NE and also a 5HT uptake tracer which involves uptake one and vesicular storage mechanisms. In rats treated with 6-hydroxydopamine to induce a chemical sympathectomy, we observed an inhibition of uptake similar for MIBG and NE in the heart, the salivary glands and the spleen, but no effect was observed in the liver. Some clinical inferences to best investigate specific monoamine uptake are drawn from these results.

[Initial antibacterial prophylaxis after bone marrow allograft. Pilot study with systemic vancomycin]

In 22 consecutive patients treated by allogenic bone marrow transplantation, the authors report their experience in complete gastrointestinal decontamination and prophylactic systemic vancomycin. Neither septicemia from the low digestive tract nor with Gram positive is noticed. A child developed septicemia with Capnocytophaga ochracea, resistant to vancomycin. There is no infectious death in this study and no significative toxicity is reported.

MIBG and catecholamine storage in the brain: an in-vitro study

The uptake and release of mIBG, a tracer of the monoamine uptake and storage function, were studied on superfused rat cerebral cortex sections. mIBG was taken up and released by a mechanism comparable to that of norepinephrine (NE), but this storage appeared to be less specific for mIBG than for NE. This implies that when mIBG is used as a scintigraphic tracer of monoaminergic synaptic vesicles, imaging should be delayed long enough to ensure release of the molecule from its nonspecific binding sites.

Central interactions between dihydropyridines and cholinergic systems in the control of blood pressure in rat

Intracerebroventricular (i.c.v.) injection of the 1,4-dihydropyridine (DHP) calcium channel agonist, Bay K8644 (30 micrograms/kg) increased mean blood pressure and the K+-evoked release of [3H]acetylcholine ([3H]ACh) from hippocampal slices in spontaneously hypertensive rats (SHR). The Bay K8644-induced hypertension was inhibited by a pretreatment with methylatropine (80 micrograms/kg i.c.v.). In SHR, nicardipine, a DHP calcium channel antagonist, reduced mean blood pressure when i.c.v. injected (10 micrograms/kg). The nicardipine-induced hypotension was reduced by a pretreatment with hemicholinium-3 (20 micrograms, i.c.v.). Nicardipine (1 microM) did not modify, in SHR, the K+-evoked release of [3H]ACh, but inhibited the Bay K8644-induced increase in the ACh release. In normotensive rats, neither Bay K8644 nor nicardipine modify blood pressure, when centrally injected, or the stimulated release of [3H]ACh from hippocampal slices. The participation of central DHP sites in the cholinergic transmission in genetic hypertension is discussed.

Characterization of dihydropyridine binding sites in the rat brain: hypertension and age-dependent modulation of [3H](+)-PN 200-110 binding

The properties of [3H]dihydropyridine (DHP), nitrendipine and (+)-PN 200-110, binding to rat cerebral membranes were investigated. In normotensive Wistar-Kyoto (WKY) adult rats, the highest densities of [3H]DHP binding sites were found in the hippocampus. Frontal cerebral cortex and hypothalamus had intermediate levels and no specific binding of [3H]DHP and [125I]iodipine could be detected in the brainstem membranes and more precisely in the nucleus tractus solitarius and in the locus coeruleus. Changes in the maximal number of DHP binding sites (Bmax) were observed in spontaneously hypertensive rats (SHR) and in old Sprague-Dawley rats. In adult SHR, there was a significant increase in the Bmax values of [3H](+)-PN 200-110 binding in the hippocampus when compared to the values obtained in WKY. There was no difference in the Bmax values between young (3 weeks) prehypertensive SHR and age-matched WKY. In senescent (26 months) Sprague-Dawley rats, the Bmax values of [3H](+)-PN 200-110 binding were significantly reduced (30%) in the frontal cerebral cortex and the hippocampus, as compared with the number of DHP binding sites found in mature Sprague-Dawley rats (15 weeks).

Central alpha 1-adrenergic and opiate systems in the control of the vagal tone in normotensive and spontaneously hypertensive rats

In anesthetized, normotensive beta-blocked rats, the alpha 1-adrenoceptor blocking drug, AR-C 239 (300 micrograms/kg, i.v.) induced a bradycardic effect related to a central increase in the vagal tone. This bradycardia was inhibited by previous administration of naloxone, intravenously (1 mg/kg) or centrally (100 micrograms/kg, i.c.) injected. Naloxone, by itself did not change the heart rate. In brainstem membranes from normotensive rats, AR-C 239 did not influence the stereoselective binding of [3H]naloxone. In spontaneously hypertensive (SH) rats, naloxone peripherally or centrally administered did not influence the activation of the vagal tone induced by AR-C 239, in beta-blocked animals. These results suggest the possible involvement of opiate release in the AR-C 239-induced vagal bradycardia, in normotensive rats. They also afford new arguments for the existence of close interactions between central alpha-adrenergic and opiate systems in the cardiovascular regulation. The possible participation of kappa-receptors in this effect is discussed. In addition, such an opiate mechanism triggered by central alpha 1-adrenoceptor blockade seems to be either absent or inactive in SH rats.

[Phenylethylamine fluorides. II. Synthesis and neurobiochemistry in the rat]

Sixteen fluorinated phenylethylamines analogous to catecholamine were obtained by fluoration from the corresponding amino-alcohols. The biological activity of the compounds was evaluated by determining their affinity for the central adrenergic receptors of rat brain membranes and by measuring the monoamine synaptosomal uptake. These compounds significantly inhibited serotonine uptake, but they showed no affinity for amphetaminergic binding sites.

Interaction between central alpha 1- and alpha 2-adrenoceptors on sympathetic tone in rats

The interaction between piperoxan and alpha 2-agonists on sympathetic tone was studied in rats. The sympatho-inhibitory effect of alpha 2-agonists (clonidine, guanfacine, B-HT 933) was assessed by recording heart rate in normotensive bilaterally-vagotomized rats. Clonidine (3 micrograms/kg, i.c.v.) and B-HT 933 (100 micrograms/kg, i.c.v.) induced a bradycardia which was fully reversed by piperoxan (30 micrograms/kg, i.c.v.). However, in rats treated with guanfacine, piperoxan induced a partial recovery of the bradycardic effect. The injection of a small dose of the specific alpha 1-adrenoceptor blocking drug, AR-C 239 (10 micrograms/kg, i.c.v.) which, by itself did not modify heart rate, completely inhibited the reversal effect of piperoxan in rats treated with clonidine, B-HT 933 or guanfacine. In rat brainstem membranes, B-HT 933 was found to bind to both alpha 1- and alpha 2-adrenoceptors and was as potent as clonidine in competing for alpha 1-sites bound by [3H]prazosin. On the other hand, in bilaterally vagotomized rats, piperoxan (30 micrograms/kg, i.c.v.) induced an increase in blood pressure and heart rate which was inhibited by previous administration of AR-C 239 (10 micrograms/kg, i.c.v.). These data suggest that, by inhibiting central alpha 2-adrenoceptors, piperoxan unmasks central alpha 1-adrenoceptor stimulation by endogenous catecholamines leading to an increase in the sympathetic tone, but a full recovery in heart rate could be observed only with the mixed alpha 1- and alpha 2-adrenoceptor agonists, clonidine and B-HT 933. In addition, these data further indicate that alpha 1-adrenoceptors are implicated in a tonic control of the sympathetic nerve activity in normotensive rats.

Meta-iodobenzylguanidine adrenal medulla localization: autoradiographic and pharmacologic studies

In order to investigate the mechanism of uptake of meta-iodobenzylguanidine (mIBG) by the adrenal glands, autoradiographic and pharmacologic studies were performed in mice and dogs receiving radioiodinated mIBG. In mice, on macroautoradiography of whole body sections 48 h after 125I-mIBG, most of the radioactivity was focused in the adrenal glands. On microautoradiography, silver grains were exclusively located in the adrenal medulla. Tissue counting after phenoxybenzamine, cocaine, and desipramine treatment resulted in 45%, 35%, and 0% inhibition of mIBG uptake, respectively. Tissue counting and scintigraphic studies demonstrated a more than 50% mIBG release from the adrenal glands after reserpine. These data indicate the high affinity of mIBG for adrenal medulla and suggest that the mIBG and catecholamine uptake mechanisms are only partially the same.

Central alpha 1-adrenoceptors and cardiovascular control in normotensive and spontaneously hypertensive rats

Intracerebroventricular (i.c.v.) injections of AR-C 239 (30 micrograms/kg), a selective alpha 1-adrenoceptor blocking drug, did not modify the heart rate in normotensive control (without pretreatment), bilaterally vagotomized and beta blocked rats and in spontaneously hypertensive (SH) bilaterally vagotomized rats. Intracisternal (i.c.) administrations of AR-C 239 (30 micrograms/kg) however decreased the heart rate in normotensive beta blocked and in SH bilaterally vagotomized rats. The differential effect on heart rate of i.c.v. versus i.c. administration of AR-C 239 suggests a brainstem localization of the alpha 1-adrenoceptors involved. The binding of [3H]prazosin was significantly higher in homogenates from whole brain and in membranes from the cerebral cortex and hypothalamus of SH rats as compared to normotensive rats. In addition, the binding of [125I]BE 2254, a new iodinated radioligand of high specific radioactivity used to characterize alpha 1-adrenoceptors, was significantly increased in membranes from the NTS of SH rats. These results suggest that central alpha 1-adrenoceptors localized in the brainstem and in the hypothalamus and the cortex play a role in the control of vagal tone in normotensive rats and of sympathetic activity in SH animals. Thus, it is postulated that central alpha 1-adrenoceptors may participate in either the genesis or the maintenance of genetic hypertension.