Surgical management of atherosclerotic carotid artery stenosis after cervical radiation therapy

Carotid surgery following external cervical irradiation has not been a treatment of choice. The purpose of this retrospective study was to describe the immediate and long-term outcome in a series of 17 consecutive patients who underwent operative treatment for carotid artery stenosis after radiation therapy. From 1989 to 1997, surgical treatment of carotid artery disease was carried out in a total of 723 patients. Seventeen of these patients, 14 men and 3 women, had undergone previous external cervical irradiation; their mean age was 61.7 years. The indication for radiation therapy was ear-nose-throat cancer in 14 patients and lymphoma in 3 patients. In 10 patients, irradiation was associated with cervical surgery. The mean delay between radiation therapy and carotid artery repair was 10 years. All 17 patients were considered to be in remission at the time of carotid repair. The indication for carotid surgery was asymptomatic stenosis in 6 cases (33%) and symptomatic stenosis in 12 (67%). The procedure consisted of endarterectomy in 12 cases (67%) and venous bypass in 6 (33%). The outcome for these patients was favorable, indicating that carotid artery repair following cervical radiation therapy is safe. Results are comparable to those of procedures performed in patients with no history of cervical irradiation.

Role of Multimodality Intraoperative Neurophysiological Monitoring during Embolisation of a Spinal Cord Arteriovenous Malformation. A Paradigmatic Case

SUMMARY

The decision whether or not to embolise during endovascular procedures for arteriovenous malformations (AVMs) of the spinal cord under general anesthesia, relies primarily on neurophysiological results of provocative tests with Lidocaine and short-acting barbiturates. Because of the complex haemodynamics of spinal AVMs, when either sensory (CSEPs) or muscle motor evoked potentials (mMEPs) are used independently, they can mislead the interpretation of provocative tests. This report illustrates the specific but complementary role played by provocative tests using CSEPs and mMEPs during embolisation of a low thoracic spinal cord AVM. We present the case of a 46 year old male with six year history of right lower extremity weakness. At that time, Magnetic Resonance (MR) imaging of the spine disclosed an intramedullary AVM at T11. He remained neurologically stable up to seven months before admission, when he developed sudden onset of low back pain, followed by progressive paraparesis, numbness in lower extremities, urinary retention and fecal incontinence. A new MR imaging study indicated venous thrombosis of the AVM. A two-stage embolisation was performed. During the first procedure, after provocative tests did not affect either CSEPs or mMEPs, an embolisation was performed through a sulcocommisure feeder from the anterior spinal artery (ASA) at T9. Conversely, provocative tests with Lidocaine performed from a right posterior spinal artery (PSA) feeder to the AVM nidus resulted in a significant (> 50%) decrease of CSEPs, while mMEPs remained unchanged. The repeatedly positive tests warranted further investigation of the vascular anatomy which disclosed a normal right PSA distal to the nidus; the distal normal PSA was protected with coils. A repeated Lidocaine test was negative and the posterior feeder was embolised with no subsequent changes in CSEPs or mMEPs. After the procedure, the patient experienced only a mild transitory increase in right leg numbness, but no additional motor deficits. Five days later, the embolisation through the ASA feeder at T9 was completed on the basis of negative provocative tests. No additional neurological deficits were observed. Favoring either CSEPs or MEPs during endovascular procedures in the spinal cord is not justified by a solid scientific background. This case report illustrates that monitoring both CSEPs and mMEPs combined with provocative tests allows the safest and most effective embolisation of spinal cord AVMs under general anesthesia.

Role of glycemia in acute spinal cord injury. Data from a rat experimental model and clinical experience

While experimental and clinical evidence indicates that in brain injury blood glucose increases with injury severity and hyperglycemia worsens neurological outcome, the role of blood glucose in secondary mechanisms of neuronal damage after acute spinal cord injury has not yet been investigated. Data from spinal cord ischemia models suggests a deleterious effect of hyperglycemia, likely due to enhanced lactic acidosis, which is primarily dependent on the amount of glucose available to be metabolized. The purpose of this study is to summarize preliminary experimental and clinical observations on the role of blood glucose in acute spinal cord injury. Between 1995 and 1996 we used the New York University (NYU) rat spinal cord injury model to test the following hypotheses: 1) Blood glucose levels increase with injury severity. 2) Fasting protects from hyperglycemia and prevents secondary damage to the spinal cord. 3) Postinjury-induced hyperglycemia (dextrose 5% 2 gm/Kg) enhances spinal lesion volume. From a clinical perspective, we reviewed blood glucose records of 47 patients admitted to the Department of Neurosrgery in Verona, between 1991 and 1995, within 24 hours of acute spinal cord injury in order to determine: a) the incidence of hyperglycemia (> 140 mg/dl); b) the correlation between blood glucose and injury severity; and c) the role of methylprednisolone in affecting blood glucose. Results indicate that in a graded spinal cord injury model: 1) Early after injury, more severe contusions support significantly higher blood glucose levels. 2) Fasting overnight does not directly affect spinal cord lesion volume but influences blood gases, and we observed that a slightly systemic acidosis plays a minor neuroprotective role. Fasting also ensures more consistent normoglycemic baseline blood glucose values. 3) Postinjury-induced moderate hyperglycemia (160-190 mg/dl) does not significantly affect spinal cord injury. In the clinical study, we observed that during the first 24 hours after spinal cord injury: a) Glycemia ranges between 90 and 243 mg/dl (mean value 143 mg/dl), and close to 50% of the patients present blood glucose values higher than normal. b) Methylprednisolone administration is not associated to significantly higher blood glucose levels. c) There is a trend for larger glucose rises with more severe injury.

Osteomyelitis of the pubic symphysis, abscess and late disjunction after delivery. A case report

Infection of the pubic symphysis after delivery is rare, and probably occurs through a small vaginal laceration and is usually silent in the early phase: as the disease progresses, bone infection, sequestra formation and septicemia man occur. This report presents one case of staphylococcal osteomyelitis of the symphysis in a twenty five years old woman, with onset of symptoms 2 months after delivery. Staphylococcus Aureus was collected from pus and blood. Bone sequestra and a large abscess extending in the rectus abdominis fascia were present. Drainage and curettage resolved infection, but sourapubic pain persisted because of symphysis disjunction, and was treated by external pelvic fixation.

Gating of alpha3beta4 neuronal nicotinic receptor can be controlled by the loop M2-M3 of both alpha3 and beta4 subunits

Previous studies have shown that the gating mechanism of alpha3beta4 neuronal nicotinic receptors is affected by a residue in the middle of the M2-M3 loop of the beta4 subunit. We have extended the study of the same location to the alpha3 subunit. Bovine alpha3beta4 receptors were mutated in position 268, substituting the residue present in wild-type receptors, i.e. leucine in alpha3 and asparagine in beta4, for an aspartate. Wild-type and mutated alpha3 and beta4 subunits were combined to form four different receptors. We have measured macroscopic currents in Xenopus oocytes elicited by nicotine, and related them to surface receptor expression measured with an epibatidine-binding essay. We also obtained single-channel recordings of the receptors to study their kinetic behaviour. The results were analysed in terms of an allosteric model with three states. We found that the effect of the mutation in the alpha3 subunit on the gating of the receptor was similar to the corresponding mutation in the beta4 subunit. The effect when both subunits were mutated was additive, suggesting that the contribution of each subunit to the gating mechanism is independent.

Embolization of a spinal arteriovenous malformation: correlation between motor evoked potentials and angiographic findings: technical case report

OBJECTIVE AND IMPORTANCE

Endovascular procedures for the treatment of spinal arteriovenous malformations place the spinal cord at risk of ischemia. This report illustrates the usefulness of motor evoked potentials (MEPs) in detecting functional changes within the spinal cord motor pathways during embolization of a spinal arteriovenous malformation under general anesthesia.

CLINICAL PRESENTATION

A 28-year-old man presented with a history of progressive lower extremity numbness and weakness followed by bladder dysfunction. Magnetic resonance imaging and angiography disclosed a T11-T12 spinal arteriovenous malformation.

INTERVENTION

During the endovascular procedure, before injection of particles, the disappearance of MEPs from the tibialis anterior muscle led to prompt angiographic reevaluation, which disclosed the arrest of spinal blood flow secondary to radiculomedullary artery occlusion by the catheter. Embolization and catheter withdrawal were followed by temporary recovery of spinal blood flow and MEPs. A second arrest of spinal cord blood flow, caused by severe vasospasm of the feeding radiculomedullary artery, was documented by a control angiogram, and its functional relevance was revealed by a second disappearance of MEPs. The therapeutic effect of papaverine infusion and induced moderate hypertension was confirmed angiographically by complete reopacification of the anterior spinal artery and confirmed neurophysiologically by the complete recovery of MEPs. At the end of the procedure, no additional neurological deficits were noted.

CONCLUSION

During spinal cord embolization, MEPs may play a critical role in early detection of spinal cord dysfunction by aiding in the prevention of damage to the spinal cord as well as by predicting the clinical outcome.

Brain tumors in children under 3 years of age. Recent experience (1987-1997) in 39 patients

Brain tumors in children under 3 years of age differ in clinical presentation and pathological behavior from those in older patients. In this study, we reviewed data from 39 children (24 males and 15 females) under 3 years of age who were treated for intracranial brain tumors since the introduction of magnetic resonance imaging. The purpose was to assess correlations between clinicoradiological and treatment-related factors, and their impact on prognosis. The following factors were analyzed: sex, age, duration of symptoms, intracranial hypertension on admission, tumor location, surgical removal and histology. Associations between these factors and correlations with prognosis were determined using bivariate analyses (chi(2) test) and Kaplan-Meier survival curves. Collins' concept of a period of risk recurrence was tested. Mean follow-up was 41 months (range 0-136). In March 1998, 20 children were still alive (51.2%) with a mean survival time of 65 months (range 2-136). The incidence of supratentorial tumors was significantly higher in children less than 1 year old (p = 0.027). Lateral tumors were 9/10 (90%) supratentorial versus only 7/26 (27%) midline tumors (p = 0.001). Outcome (dead or alive) was significantly better (p = 0.037) for low-grade astrocytomas (9/12 = 75% survival) when compared to ependymomas (2/6 = 33%) and primitive neuroectodermal tumors (3/12 = 25%). Total tumor removal was achieved in 20 cases and was associated with a better outcome (65 vs. 33% survival; p = 0.049). Survival analysis confirmed a worse prognosis for children with ependymomas and primitive neuroectodermal tumors (p = 0.011) and revealed a worse survival for children with intracranial hypertension on admission (p = 0.047). Total tumor removal was associated with a longer survival, although not significantly (p = 0. 077). Finally, we found no exceptions to Collins' law.

[Carotid angioplasty: review of the literature]

PURPOSE

In order to assess the current knowledge of carotid angioplasty and stenting, we reviewed the pertinent literature distinguishing two types of reports on angioplasty for atherosclerotic stenosis of the internal carotid artery: case reports and series with less than 10 cases, and series reporting more than 10 cases.

METHODS

Each series was examined individually followed by a general analysis.

RESULTS

The 11 largest series in the literature included a total of 912 patients. The rate of transient ischemic attacks ranged from 6 to 14.8%. Stroke rate varied from 1.5 to 9.1%. Restenosis was reported in 4 to 16% of cases.

CONCLUSION

Based on the data available in the literature, we cannot recommend carotid angioplasty. Carotid endarterectomy is recognised as safe and is generally considered to be the gold standard. In order to assess carotid angioplasty and stenting accurately, prospective randomized studies comparing surgery and angioplasty are necessary.

Intracranial myxoid chondrosarcoma with early intradural growth

Chondrosarcomas are extremely rare intracranial cartilaginous tumors of which the myxoid variant is the least reported in the literature. They develop extradurally and generally infiltrate the dura only in advanced stages or at recurrence. We describe the case of a 55-year-old woman with a posterior cranial fossa myxoid chondrosarcoma which had a primarily intradural extension.

A residue in the middle of the M2-M3 loop of the beta4 subunit specifically affects gating of neuronal nicotinic receptors

An aspartate residue in the M2-M3 loop of neuronal nicotinic receptor alpha7 subunits is a major determinant of the channel functional response. This residue is conserved in most beta4 subunits, e.g. human and rat, but not in others, e.g. bovine. We have used these differences to examine the mechanism by which this residue alters the functional properties of alpha3beta4 receptors. Having ruled out an effect on the macroscopic binding ability of the agonist, the level of receptor expression, or the single channel conductance, the results suggest that receptors lacking that residue have a deficient coupling between binding and gating.

Anterior gonalgic syndrome after intramedullary nailing: ultrasound and radiologic study

A total of 33 patients submitted to tibial intramedullary osteosynthesis for fracture (27 cases) and non-union were assessed by ultrasound and x-rays an average of 10.9 months after surgery. The route of access was patellar transtendineal in each case; the means of synthesis used was the Marchetti Vicenzi nail. In 19 patients (57.6%) there was anterior gonalgia. Radiologic assessment evaluated prominence of the nail, while nail-tendon impingement was examined by ultrasound. Nail-tendon impingement was frequently observed (24 cases, 72.7%); in cases such as these anterior pain in the knee was present in 17 patients: however, this fact did not achieve statistical significance. The patellar tendon was thickened as compared to the contralateral one, with disorganization of the fibrillar echotexture, but it was not shortened. The tendinous morphostructure did not reveal any relationship with anterior gonalgia. In none of the cases did we observe the formation of scarring nuromas. In the area of the Hoffa body reactive synovitis phenomena with structural hyperechogenicity, an unclear aspect of the posterior tendinous profile and calcifications were observed. Radiographic prominence of the nail was correlated with echographic impingement, but not with clinical findings. Removal of the instrumentation carried out in 8 patients characterized by anterior gonalgia did not lead to resolution of symptoms in 2 cases in which MRI study showed patellar tendinitis and in 1 case patellar chondropathy with irregularity of the Hoffa body in the second.

[Treatment of iliac artery stenosis and obliteration by transluminal angioplasty]

PURPOSE

Percutaneous transluminal angioplasty (PTA) has an established and valuable role in the treatment of iliac stenoses and occlusions. The use of stents may improve the results of PTA. The aim of this study is to report our surgical experience of iliac angioplasty over the past 5 years.

PATIENTS AND METHODS

From January 1993 to October 1997, 201 iliac PTA were performed in 175 patients, at the level of the common iliac artery (n = 111) and external iliac artery (n = 90). In 26 cases, two iliac lesions were treated simultaneously. There were 188 stenoses and 13 chronic occlusions. During PTA, 55 stents were used, because of unsatisfactory results (dissection, residual stenosis) or in case of total occlusion, in the common iliac artery in 35 cases and in the external iliac artery in 20 cases. In 15 cases (8.6%), a femoro-popliteal bypass was associated to the iliac PTA, because of multilevel occlusive disease.

RESULTS

There were no early deaths. There were seven initial failures. The initial success rate was 96%. The clinical follow-up has been achieved in 163 patients, (range: 3 to 48 months, mean: 28 months). The primary patency rates were 84%, 79% and 63% respectively at 1, 2, and 4 years. The secondary patency rates were 87%, 85% and 73% respectively at 1, 2, and 4 years.

Prognostic factors in childhood intracranial ependymomas: the role of age and tumor location

Despite several clinical reports on intracranial ependymomas in children, the factors which affect prognosis, and the possibility that certain combinations of factors might limit survival, are still a matter of debate. Between 1976 and 1996 we operated on 35 children with intracranial ependymomas. Postoperative irradiation was given to 27 patients, with associated chemotherapy in 6 cases. Mean follow-up was 62 months. In 12 patients a 5-year follow-up was possible. In October 1996, 18 patients (51.4%) were still alive, the longest disease-free follow-up being 20 years, and the shortest 8 months. We analyzed the prognostic relevance of eight factors. For each factor, different subgroups were distinguished and compared as follows: age at diagnosis (<4 vs. >/=4 years), sex, tumor location (supratentorial vs. infratentorial), tumor size (<4 vs. 4-7 vs. >7 cm), surgical removal (total vs. subtotal), histology (low-grade vs. anaplastic), morphology (solid vs. cystic), adjuvant therapies (treatment vs. no treatment). Two-way contingency tables were made to identify associations between variables. The only significant association was between age and tumor location (p = 0.022): in children under 4, tumors were almost invariably located in the posterior fossa (9 out of 10 cases) with a clear preference for the lateral recess (8 cases). Other correlations were not significant. Kaplan-Meier survival curves were compared to assess the prognostic relevance of each factor. Survival was significantly lower for children under 4, for those with posterior fossa tumors, and for patients with residual tumor (p < 0.05). A multivariate analysis compared variables which significantly affected survival, revealing that age is the most important factor affecting prognosis (p < 0.05), while tumor location and surgical removal do not add any significance to the effect of age on survival. We conclude that age has the strongest prognostic relevance in childhood intracranial ependymomas, while the effect of tumor location on survival may be related to the high incidence of lateral recess ependymomas in younger children.

Assessment and surgical management of posterior fossa epidermoid tumors: report of 28 cases

OBJECTIVE

The management of a series of 28 patients operated on for posterior fossa epidermoids is reviewed, emphasizing the need for long-term follow-up. We discuss the rationale for a comprehensive classification system that may allow the comparison of results from homogeneous series.

METHODS

We grouped the tumors to differentiate the surgical management according to various tumor sites and the degree of extension. Twenty patients harbored tumors located in the cerebellopontine angle, five patients harbored tumors in the fourth ventricle, and three patients harbored tumors in the posterior fossa basal. In 17 patients, extensions of tumors outside the posterior fossa included the following regions: the suprasellar/ chiasmatic (n = 5), the parasellar/temporobasal (n = 5), and the mesencephalic/pineal (n = 7). Tumor extension was also defined by the number of regions involved. Pre- and postoperative magnetic resonance imaging and computed tomographic findings collected in 17 and 28 patients, respectively, were carefully evaluated.

RESULTS

Clinical features and surgical approaches varied according to location and growth pattern. Fifty-seven percent of the tumors were completely removed. A higher total removal rate was achieved in patients with tumors confined to the primary location. One patient (3%) died in the perioperative period. Approximately half of the patients presented with transient mild focal deficit impairments resulting from the manipulation of the nervous structure over a wide area. There was a higher rate of surgical complications with fourth ventricle and mesencephalic extended cerebellopontine angle tumors. The mean follow-up period was 8.6 years. Thirty percent of the patients with subtotal removal experienced symptomatic recurrences after 8.1 years, whereas all patients with total removal were still asymptomatic. The recurrence-free survival rate was 95% at 13 years for patients with total removal compared with 65% for patients with subtotal removal. Problems of identification of tumor regrowth are discussed.

CONCLUSION

By assessing posterior fossa epidermoids, we determined that location and extension play a major role in the prognosis. Our data suggest that more aggressive surgery is called for at first operation, and that a second operation should be planned when regrowth becomes symptomatic and/or tends to extend outside its original site.

Role of the putative transmembrane segment M3 in gating of neuronal nicotinic receptors

The involvement of some structural domains in the gating of the neuronal nicotinic acetylcholine receptor (AChR) was studied by expressing functional alpha7/alpha3 chimeric subunits in Xenopus oocytes. Substitution of the M3 transmembrane segment in the alpha7 subunit modifies the kinetic properties of the chimeric AChRs as follows: (a) a 6-fold reduction in the maximal current evoked by nicotinic agonists, (b) a 10-fold decrease in the macroscopic desensitization rate, (c) an increase of almost 1 order of magnitude in the apparent affinity for acetylcholine and nicotine, and (d) a decrease in the affinity for alpha-bungarotoxin. Computer simulations showed that the first three effects could be accounted for by a simple kinetic model in which chimeric AChRs presented a smaller ratio of the gating rates, beta/alpha, and a slightly slower desensitization rate. It is concluded that the M3 domain influences the gating of neuronal AChRs.

Neuronal nicotinic acetylcholine receptors on bovine chromaffin cells: cloning, expression, and genomic organization of receptor subunits

Neuronal nicotinic acetylcholine receptors from bovine adrenomedullary chromaffin cells play a primary role in triggering catecholamine secretion. In the present study, their constituent subunits were characterized. In addition to the alpha 3 subunit, which we have previously cloned, the presence of alpha 5 and beta 4 but not of beta 2 subunits was detected by reverse transcription-PCR analysis of mRNA from adrenal medulla. In situ hybridization indicated that alpha 3, alpha 5, and beta 4 subunits are coexpressed in all chromaffin cells. The primary structure of alpha 5 and beta 4 subunits was determined and functional receptors were obtained upon coinjection of subunit cRNAs into Xenopus oocytes. In contrast to other beta 4-containing nicotinic receptors, the ones formed by the bovine beta 4 subunit are insensitive to the agonist cytisine. Finally, we characterized the intergenic region of alpha 3 and alpha 5 subunits, which together with the beta 4 subunit, form a gene cluster in rats and chickens. RNase assays and the existence of overlapping cDNAs indicate that, in the bovine genome, the alpha 3 and alpha 5 genes overlap at their 3' ends. This fact is probably due to inefficient transcription termination, as a result of weak polyadenylation signals.

Acetylcholine receptor subunit homomer formation requires compatibility between amino acid residues of the M1 and M2 transmembrane segments

The neuronal nicotinic acetylcholine receptor (nAChR) subunits alpha3 and alpha7 have different assembly behavior when expressed in heterologous expression systems: alpha3 subunits require other subunits to assemble functional nAChRs, whereas alpha7 subunits can produce homomeric nAChRs. A previous analysis of alpha7/alpha3 chimeric constructs identified a domain comprising the first putative membrane-spanning segment, M1, as essential to homomeric assembly. The present study dissected further this domain, identifying three amino acid residues, which are located at the most intracellular third of the M1 transmembrane segment, as important in the assembly of homomers. Moreover, formation of homooligomeric complexes seems to require a compatible accommodation between this region and certain residues of the second transmembrane segment, M2. Thus, compatibility between defined domains of the M1 and M2 transmembrane segments appears as a determinant factor governing homomer association of nAChR subunits.

Comparative toxicology of two enantiomers of the peripherally acting non-narcotic antitussive drug moguisteine

Moguisteine (R,S(+/-)-2-(2-methoxyphenoxy)-methyl-3-ethoxycarbonylacetyl-1,3-t hiazolidine, CAS 119637-67-1), a new peripheral non-narcotic antitussive drug, is a racemate composed of an equimolar mixture of R(+) and S(-) enantiomers (BBR 2221 and BBR 2222, respectively). Since in some cases the use of only one enantiomer instead of a racemate may increase the efficacy and/or the tolerability of a compound, moguisteine enantiomers were submitted to toxicological evaluation. Given in a single oral (gavage) or intraperitoneal administration to mice and rats, both moguisteine enantiomers show very low general toxicity. Administered by gavage to rats and dogs for four consecutive weeks, BBR 221 and BBR 2222 are tolerated at up to the dose of 240 mg/kg/day in both sexes with no appreciable toxic changes. Finally, the mutagenicity tests show that both enantiomers are devoid of any mutagenic potential both in vitro and in vivo. Considering the overall results of the toxicological studies and comparing them with the data obtained from the previously performed studies with the racemate moguisteine, it can be affirmed that no differences can be identified between the two enantiomers and the racemate moguisteine. These findings justify the development of moguisteine as a racemate since neither enantiomer should offer any advantage over the racemate.

Inhibition of nicotinic receptor-mediated responses in bovine chromaffin cells by diltiazem

1. The effects of diltiazem on various functional parameters were studied in bovine cultured adrenal chromaffin cells stimulated with the nicotinic receptor agonist dimethylphenylpiperazinium (DMPP) or with depolarizing Krebs-HEPES solutions containing high K+ concentrations. 2. The release of [3H]-noradrenaline induced by DMPP (100 microM for 5 min) was gradually and fully inhibited by increasing concentrations of diltiazem (IC50 = 1.3 microM). In contrast, the highest concentration of diltiazem used (10 microM) inhibited the response to high K+ (59 mM for 5 min) by only 25%. 3. 45Ca2+ uptake into cells stimulated with DMPP (100 microM for 1 min) was also blocked by diltiazem in a concentration-dependent manner (IC50 = 0.4 microM). Again, diltiazem blocked the K(+)-evoked 45Ca2+ uptake (70 mM K+ for 1 min) only by 20%. In contrast, the N-P-Q-type Ca2+ channel blocker omega-conotoxin MVIIC depressed the K+ signal by 70%. In the presence of this toxin, diltiazem exhibited an additional small inhibitory effect, indicating that the compound was acting on L-type Ca2+ channels. 4. Whole-cell Ba2+ currents through Ca2+ channels in voltage-clamped chromaffin cells were inhibited by 3-10 microM diltiazem by 20-25%. The inhibition was readily reversed upon washout of the drug. 5. The whole-cell currents elicited by 100 microM DMPP (IDMPP) were inhibited in a concentration-dependent and reversible manner by diltiazem. Maximal effects were found at 10 microM, which reduced the peak IDMPP by 70%. The area of each curve represented by total current (QDMPP) was reduced more than the peak current. At 10 microM, the inhibition amounted to 80%; the IC50 for QDMPP inhibition was 0.73 microM, a figure close to the IC50 for 45Ca2+ uptake (0.4 microM) and [3H]-noradrenaline release (1.3 microM). The blocking effects of diltiazem developed very quickly and did not exhibit use-dependence; thus the drug blocked the channel in its closed state. The blocking effects of 1 microM diltiazem on IDMPP were similar at different holding potentials (inhibition by around 30% at -100, -80 or -50 mV). Diltiazem did not affect the current flow through voltage-dependent Na+ channels. 6. These data are compatible with the idea that diltiazem has little effect on Ca2+ entry through voltage-dependent Ca2+ channels in bovine chromaffin cells. Neither, does diltiazem affect INa. Rather, diltiazem acts directly on the neuronal nicotinic receptor ion channel and blocks ion fluxes, cell depolarization and the subsequent Ca2+ entry and catecholamine release. This novel effect of diltiazem might have clinical relevance since it might reduce the sympathoadrenal drive to the heart and blood vessels, thus contributing to the well established antihypertensive and cardioprotective effects of the drug.