Impact of Nebulization on the Physicochemical Properties of Polymer-Lipid Hybrid Nanoparticles for Pulmonary Drug Delivery

Nanoparticles (NPs) have shown significant potential for pulmonary administration of therapeutics for the treatment of chronic lung diseases in a localized and sustained manner. Nebulization is a suitable method of NP delivery, particularly in patients whose ability to breathe is impaired due to lung diseases. However, there are limited studies evaluating the physicochemical properties of NPs after they are passed through a nebulizer. High shear stress generated during nebulization could potentially affect the surface properties of NPs, resulting in the loss of encapsulated drugs and alteration in the release kinetics. Herein, we thoroughly examined the physicochemical properties as well as the therapeutic effectiveness of Infasurf lung surfactant (IFS)-coated PLGA NPs previously developed by us after passing through a commercial Aeroneb® vibrating-mesh nebulizer. Nebulization did not alter the size, surface charge, IFS coating and bi-phasic release pattern exhibited by the NPs. However, there was a temporary reduction in the initial release of encapsulated therapeutics in the nebulized compared to non-nebulized NPs. This underscores the importance of evaluating the drug release kinetics of NPs using the inhalation method of choice to ensure suitability for the intended medical application. The cellular uptake studies demonstrated that both nebulized and non-nebulized NPs were less readily taken up by alveolar macrophages compared to lung cancer cells, confirming the IFS coating retention. Overall, nebulization did not significantly compromise the physicochemical properties as well as therapeutic efficacy of the prepared nanotherapeutics.

Development and characterization of lung surfactant-coated polymer nanoparticles for pulmonary drug delivery

Lung cancer is often diagnosed at an advanced stage where tumors are usually inoperable and first-line therapies are inefficient and have off-targeted adverse effects, resulting in poor patient survival. Here, we report the development of an inhalable poly lactic-co-glycolic acid polymer-based nanoparticle (PLGA-NP) formulation with a biomimetic Infasurf® lung surfactant (LS) coating, for localized and sustained lung cancer drug delivery. The nanoparticles (188 ± 7 nm) were stable in phosphate buffered saline, serum and Gamble's solution (simulated lung fluid), and demonstrated cytocompatibility up to 1000 μg/mL concentration and dose-dependent uptake by lung cancer cells. The LS coating significantly decreased nanoparticle (NP) uptake by NR8383 alveolar macrophages in vitro compared to uncoated NPs. The coating, however, did not impair NP uptake by A549 lung adenocarcinoma cells. The anti-cancer drug gemcitabine hydrochloride encapsulated in the PLGA core was released in a sustained manner while the paclitaxel loaded in the LS shell demonstrated a rapid or burst release profile over 21 days. The drug-loaded NPs significantly decreased cancer cell survival and colony formation in vitro compared to free drugs and single drug-loaded NPs. In vivo studies confirmed greater retention of LS-coated NPs in the lungs of C57BL/6 WT mice compared to uncoated NPs, at 24 h and 72 h following intranasal administration. The overall results confirm that LS coating is a unique strategy for cloaking polymeric NPs to potentially prevent their rapid lung clearance and facilitate prolonged pulmonary drug delivery.

Synthesis and characterization of a novel pH-responsive drug-releasing nanocomposite hydrogel for skin cancer therapy and wound healing

Local skin cancer recurrence occurs in ∼12% of the patients post-surgery due to persistent growth of residual cancer cells. Wound infection is another significant complication following surgery. We report a novel in situ-forming nanocomposite hydrogel (NCH) containing PLGA-carboxymethyl chitosan nanoparticles (186 nm) for localized pH-responsive skin cancer therapy and wound healing. This injectable hydrogel, comprising of a citric acid-derived polymer backbone, gelled within 5 minutes, and demonstrated excellent swelling (283% of dry weight) and compressive strengths (∼5.34 MPa). Nanoparticle incorporation did not significantly affect hydrogel properties. The NCH effluents were cytocompatible with human dermal fibroblasts at 500 μg ml-1 concentration and demonstrated pH-dependent drug release and promising therapeutic efficacy against A431 and G361 skin cancer cells in vitro. Significant zones of inhibition were observed in S. aureus and E. coli cultures on NCH treatment, confirming its antibacterial properties. Our studies show that the pH-responsive NCH can be potentially used for adjuvant skin cancer treatment and wound healing.

Emerging drug delivery strategies for idiopathic pulmonary fibrosis treatment

Idiopathic pulmonary fibrosis (IPF) is a debilitating and fatal condition that causes severe scarring of the lungs. While the pathogenesis of IPF continues to be extensively studied and several factors have been considered, an exact cause has yet to be established. With inadequate treatment options and no cure available, overall disease prognosis is still poor. Existing oral therapies, pirfenidone and nintedanib, may attempt to improve the patients' quality of life by mitigating symptoms and slowing disease progression, however chronic doses and systemic deliveries of these drugs can lead to severe side effects. The lack of effective treatment options calls for further investigation of restorative as well as additional palliative therapies for IPF. Nanoparticle-based sustained drug delivery strategies can be utilized to ensure targeted delivery for site-specific treatment as well as long-acting therapy, improving overall patient compliance. This review provides an update on promising strategies for the delivery of anti-fibrotic agents, along with an overview of key therapeutic targets as well as relevant emerging therapies currently being evaluated for IPF treatment.

Current State of Breast Cancer Diagnosis, Treatment, and Theranostics

Breast cancer is one of the leading causes of cancer-related morbidity and mortality in women worldwide. Early diagnosis and effective treatment of all types of cancers are crucial for a positive prognosis. Patients with small tumor sizes at the time of their diagnosis have a significantly higher survival rate and a significantly reduced probability of the cancer being fatal. Therefore, many novel technologies are being developed for early detection of primary tumors, as well as distant metastases and recurrent disease, for effective breast cancer management. Theranostics has emerged as a new paradigm for the simultaneous diagnosis, imaging, and treatment of cancers. It has the potential to provide timely and improved patient care via personalized therapy. In nanotheranostics, cell-specific targeting moieties, imaging agents, and therapeutic agents can be embedded within a single formulation for effective treatment. In this review, we will highlight the different diagnosis techniques and treatment strategies for breast cancer management and explore recent advances in breast cancer theranostics. Our main focus will be to summarize recent trends and technologies in breast cancer diagnosis and treatment as reported in recent research papers and patents and discuss future perspectives for effective breast cancer therapy.

Porous Polymeric Microspheres With Controllable Pore Diameters for Tissue Engineered Lung Tumor Model Development

Complex cell cultures are more representative of in vivo conditions than conventionally used monolayer cultures, and are hence being investigated for predictive screening of therapeutic agents. Poly lactide co-glycolide (PLGA) polymer is frequently used in the development of porous substrates for complex cell culture. Substrates or scaffolds with highly interconnected, micrometric pores have been shown to positively impact tissue model formation by enhancing cell attachment and infiltration. We report a novel alginate microsphere (AMS)-based controlled pore formation method for the development of porous, biodegradable PLGA microspheres (PPMS), for tissue engineered lung tumor model development. The AMS porogen, non-porous PLGA microspheres (PLGAMS) and PPMS had spherical morphology (mean diameters: 10.3 ± 4, 79 ± 21.8, and 103 ± 30 μm, respectively). The PPMS had relatively uniform pores and a porosity of 45.5%. Degradation studies show that PPMS effectively maintained their structural integrity with time whereas PLGAMS showed shrunken morphology. The optimized cell seeding density on PPMS was 25 × 103 cells/mg of particles/well. Collagen coating on PPMS significantly enhanced the attachment and proliferation of co-cultures of A549 lung adenocarcinoma and MRC-5 lung fibroblast cells. Preliminary proof-of-concept drug screening studies using mono- and combination anti-cancer therapies demonstrated that the tissue-engineered lung tumor model had a significantly higher resistance to the tested drugs than the monolayer co-cultures. These studies indicate that the PPMS with controllable pore diameters may be a suitable platform for the development of complex tumor cultures for early in vitro drug screening applications.

Ultrasound-Enhanced Chemiluminescence for Bioimaging

Tissue imaging has emerged as an important aspect of theragnosis. It is essential not only to evaluate the degree of the disease and thus provide appropriate treatments, but also to monitor the delivery of administered drugs and the subsequent recovery of target tissues. Several techniques including magnetic resonance imaging (MRI), computational tomography (CT), acoustic tomography (AT), biofluorescence (BF) and chemiluminescence (CL), have been developed to reconstruct three-dimensional images of tissues. While imaging has been achieved with adequate spatial resolution for shallow depths, challenges still remain for imaging deep tissues. Energy loss is usually observed when using a magnetic field or traditional ultrasound (US), which leads to a need for more powerful energy input. This may subsequently result in tissue damage. CT requires exposure to radiation and a high dose of contrast agent to be administered for imaging. The BF technique, meanwhile, is affected by strong scattering of light and autofluorescence of tissues. The CL is a more selective and sensitive method as stable luminophores are produced from physiochemical reactions, e.g. with reactive oxygen species. Development of near infrared-emitting luminophores also bring potential for application of CL in deep tissues and whole animal studies. However, traditional CL imaging requires an enhancer to increase the intensity of low-level light emissions, while reducing the scattering of emitted light through turbid tissue environment. There has been interest in the use of focused ultrasound (FUS), which can allow acoustic waves to propagate within tissues and modulate chemiluminescence signals. While light scattering is decreased, the spatial resolution is increased with the assistance of US. In this review, chemiluminescence detection in deep tissues with assistance of FUS will be highlighted to discuss its potential in deep tissue imaging.

Absolute calibration of GafChromic film for very high flux laser driven ion beams

We report on the calibration of GafChromic HD-v2 radiochromic film in the extremely high dose regime up to 100 kGy together with very high dose rates up to 7 × 10¹¹ Gy/s. The absolute calibration was done with nanosecond ion bunches at the Neutralized Drift Compression Experiment II particle accelerator at Lawrence Berkeley National Laboratory (LBNL) and covers a broad dose dynamic range over three orders of magnitude. We then applied the resulting calibration curve to calibrate a laser driven ion experiment performed on the BELLA petawatt laser facility at LBNL. Here, we reconstructed the spatial and energy resolved distributions of the laser-accelerated proton beams. The resulting proton distribution is in fair agreement with the spectrum that was measured with a Thomson spectrometer in combination with a microchannel plate detector.

Incidence of symptomatic venous thromboembolism following hematopoietic stem cell transplantation

BACKGROUND

The incidence of symptomatic venous thromboembolism (VTE) following hematopoietic stem cell transplantation (HSCT) is not well described, particularly with increased use of ambulatory care in the transplant setting.

METHODS

A retrospective analysis involving 589 patients (382 autologous HSCT, 207 allogeneic HSCT) undergoing transplantation between 2000 and 2005 in a single Canadian institution was undertaken to identify the incidence of proximal deep vein thrombosis (DVT) or pulmonary embolism (PE) in HSCT patients.

RESULTS

The total 1-year incidence of symptomatic VTE was 3.7% [95% confidence interval (CI) 2.5-5.6]. Among the HSCT patients, 7/589 (1.2%, 95% CI 0.6-2.4) developed symptomatic non-catheter-related VTE following HSCT (four PE and three DVT). All VTE events occurred after hematopoietic engraftment. Patients undergoing autologous HSCT did not receive thromboprophylaxis, whereas most patients undergoing allogeneic HSCT (79.7%) received enoxaparin 20 mg daily for the prevention of veno-occlusive disease of the liver, starting 6 +/- 3 days before transplantation for a mean of 22 +/- 14 days.

CONCLUSION

HSCT patients have a high incidence of VTE. Thromboprophylaxis should potentially be considered in these patients. However, future studies assessing the risk and benefits of thromboprophylaxis are needed in this specific population.

Fractionated stereotactic conformal radiotherapy for secreting and nonsecreting pituitary adenomas

OBJECTIVE

To assess the medium-term outcome in a cohort of patients with residual or recurrent pituitary adenoma treated with fractionated stereotactic conformal radiotherapy (SCRT).

PATIENTS AND METHODS

Ninety-two patients (median age 50 years) with a residual or recurrent nonfunctioning (67) or a secreting (25) pituitary adenoma were treated between 1995 and 2003. Eighteen patients had a GH-secreting, five PRL-secreting and two an ACTH-secreting pituitary adenoma. Vision was impaired in 39 patients, with visual field deficit (35) and/or reduced visual acuity (25). Sixty-four patients had partial or complete hypopituitarism before SCRT. The treatment was delivered stereotactically by four noncoplanar conformal fixed fields using a 6-MV linear accelerator to a dose of 45 Gy in 25 fractions.

RESULTS

At a median follow-up of 32 months (range 4-108) the 1, 3 and 5 years actuarial progression-free survival is 99%, 98% and 98%, and overall survival is 98%. Three patients recurred 5 months, 1 year and 9 years after SCRT requiring surgery. In secreting adenomas, hormone levels declined progressively, becoming normal in more than a third of patients with GH-secreting and PRL-secreting pituitary tumours. 50% of baseline GH level was achieved in just under 2 years. The treatment was well tolerated with minimal acute toxicity. Hypopituitarism was the most common long-term effect; 22% of patients had worsening of pituitary function. One patient developed unilateral quadrantopia without tumour progression.

CONCLUSION

SCRT as a high-precision technique of localized irradiation achieves tumour and hormone control of pituitary adenomas comparable with previously published data on the efficacy of conventional radiotherapy. Despite the potential advantage of reducing the volume of normal brain irradiated, the theoretical benefit over conventional radiotherapy in terms of the reduction in long-term morbidity has not yet been demonstrated and requires longer follow-up. Potential effect on long-term cognitive function has not been tested.

Neoadjuvant phase II multicentre study of new agents in patients with malignant glioma after minimal surgery. Report of a cohort of 187 patients treated with temozolomide

BACKGROUND

The aim of this study was to assess the efficacy of new agents in patients with malignant glioma in a neoadjuvant setting not confounded by surgery. The first study of neoadjuvant temozolomide aimed to provide a benchmark for future evaluation of new treatments.

PATIENTS AND METHODS

This was a multicentre phase II study of chemotherapy in patients with histologically verified glioblastoma multiforme (GBM) and anaplastic astrocytoma (AA) who had undergone biopsy alone. Patients were planned to receive two cycles of temozolomide at 200 mg/m(2) orally daily for 5 days at a 28-day interval prior to radiotherapy. Response was assessed by two central observers on pre- and post-chemotherapy enhanced scans using bi-dimensional criteria and as progression-free survival (PFS) at the time of second assessment prior to radiotherapy. Withdrawal from the study due to worsening clinical condition was, in the absence of second imaging, assessed as progressive disease. Survival and quality of life (QOL) were secondary endpoints.

RESULTS

Between August 1999 and June 2002, 188 patients from 15 UK and two Italian centres were entered into the study and 187 were analysed. Overall, 162 patients were assessable for response; seven had partial and 25 had minimal response. The objective response rate was 20% [95% confidence interval (CI) 14-26%] and PFS prior to commencing radiotherapy was 64% (95% CI 57-72%). The median survival was 10 months, and 1-year survival 41%. The median survival of responders was 16 months compared to 3 months in patients with progressive disease (P <0.001 on multivariate analysis).

CONCLUSION

The phase II study design of primary chemotherapy in patients with malignant glioma following biopsy alone is feasible and provides as objective a method of assessment of efficacy as is currently available. The baseline data on temozolomide provide a benchmark for assessment of efficacy of other agents and combinations.

Risk of second brain tumor after conservative surgery and radiotherapy for pituitary adenoma: update after an additional 10 years

We assessed the risk of second brain tumors in a cohort of patients with pituitary adenoma treated with conservative surgery and external beam radiotherapy. Four hundred and twenty-six patients (United Kingdom residents) with pituitary adenomas received radiotherapy at the Royal Marsden Hospital (RMH) between 1962 and 1994. They were followed up for 5749 person-years. The cumulative incidence of second intracranial tumors and systemic malignancy was compared with population incidence rates through the Thames Cancer Registry and the National Health Service Central Register (previously OPCS) to record death and the potential causes. Eleven patients developed a second brain tumor, including five meningiomas, four high grade astrocytomas, one meningeal sarcoma, and one primitive neuroectodermal tumor. The cumulative risk of second brain tumors was 2.0% [95% confidence interval (CI), 0.9-4.4%] at 10 yr and 2.4% (95% CI, 1.2-5.0%) at 20 yr, measured from the date of radiotherapy. The relative risk of second brain tumor compared with the incidence in the normal population was 10.5 (95% CI, 4.3-16.7). The relative risk was 7.0 for neuroepithelial and 24.3 for meningeal tumors. The relative risks were 24.2 (95% CI, 4.8-43.5), 2.9 (95% CI, 0-8.5), and 28.6 (95% CI, 0.6-56.6) during the intervals 5-9, 10-19, and more than 20 yr after radiotherapy (four cases occurred >20 yr after treatment). There was no evidence of excess risk of second systemic malignancy. An additional 10-yr update confirmed our previous report of an increased risk of second brain tumors in patients with pituitary adenoma treated with surgery and radiotherapy. The 2.4% risk at 20 yr remains low and should not preclude the use of radiotherapy as an effective treatment option. However, an increased risk of second brain tumors continues beyond 20 and 30 yr after treatment.

Phase II study of primary temozolomide chemotherapy in patients with WHO grade II gliomas

BACKGROUND

The aim of this study was to assess the efficacy of temozolomide in patients with World Health Organisation (WHO) grade II gliomas treated with surgery alone using imaging and clinical criteria.

PATIENTS AND METHODS

Thirty patients with histologically verified WHO grade II gliomas (17 astrocytoma, 11 oligodendroglioma, two mixed oligoastrocytoma) following surgery 2-104 months (median 23 months) after initial diagnosis received temozolomide 200 mg/m(2)/day for 5 days, on a 28-day cycle, for a maximum of 12 cycles or until tumour progression. Median age was 40 years (range 25-68 years). Median follow-up from entry into the study was 3 years [range 23-47 months (for patients alive)]. Objective response was assessed by 3-monthly magnetic resonance imaging and monthly health-related quality of life (HQoL) and clinical assessment. Tumour size was measured as the high signal intensity area on fluid attenuated inversion recovery sequences. Responses were assessed using change in the product of two perpendicular diameters as complete response (CR), partial response (PR), minimal response (MR), stable disease (SD) and progressive disease (PD).

RESULTS

Twenty-nine of 30 patients entered into the study were evaluable for response. Three patients had a PR, 14 MR, 11 SD and one PD. Twenty-four patients received 12 cycles of chemotherapy. Of 29 evaluable patients, three discontinued after four, five and six cycles and two after 10 cycles. Nine patients progressed (three during chemotherapy-one PD and two initial SD-and six after completion of chemotherapy); five had evidence of transformation. The 3-year progression-free survival was 66%. Five patients died; the actuarial 3-year survival was 82%. Ninety-six per cent of patients with impaired HQoL had improvement in at least one HQoL domain. There was improvement in 115 of the 207 domains (56%). Fifteen of 28 patients (54%) with epilepsy had reduction in seizure frequency, of whom six became seizure free. Six patients had transient grade III/IV haematological toxicity (11 episodes; 3.5%).

CONCLUSIONS

Temozolomide has single-agent activity in patients with WHO grade II cerebral glioma, with modest improvement in quality of life and improvement in epilepsy control. On present evidence, temozolomide cannot be considered as primary therapy without formal comparison with other treatment modalities.

[Adjuvant therapy with a glycoprotein IIb-IIa inhibitor (abciximab) in coronary angioplasties with a high thrombotic risk]

INTRODUCTION

We retrospectively studied our experience with adjunctive therapy with glycoprotein IIb-IIIa inhibitor (abciximab) on patients with a high risk of thrombotic complications during coronary angioplasty (PTCA).

PATIENTS AND METHODS

From September 1996 to November 1997, we performed PTCA in 210 patients, and abciximab was given to 38 (18%) of them. The interventions were urgent (primary PTCA in acute myocardial infarction) in 55% of the cases. The mean age of patients was 68.6 +/- 12 years and 71% were male. The reasons for coronary intervention were: acute myocardial infarction in 21 patients (55.3%), unstable angina in 9 (23.7%) and stable angina in 8 (21%). Coronary stents were implanted in 13 patients (34%) and an intra aortic balloon pump was used in 4 (11%). The reasons for using abciximab were: thrombus containing lesion: 22 (57.9%); other type B2/C lesion characteristics: 6 (15.9%); acute closure post balloon PTCA: 9 (23.7%), sub-acute stent thrombosis: 1 (2.6%). Oral acetilsalicilic acid and intravenous heparin were given to all patients at the beginning of the intervention. The mean APTT was 124 +/- 32 seconds at the end of the procedure.

RESULTS

The arterial sheaths (8 French) were removed six hours after procedure, according to the normalisation of APTT values. Angiographic success in this group of patients was 100%. One patient died during hospitalisation due to left ventricular failure. There was no need for repeated angioplasty or coronary bypass grafting during hospital stay. The main complications related to the use of abciximab were: bleeding (requiring transfusion) in four patients 10.5%); severe thrombocytopenia (< 50,000 platelets/mm3): 1 (2.6%): cardiac tamponade (requiring pericardiocentesis): 1 (2.6%) and pseudo-aneurysm of femoral artery (requiring vascular surgery): 1 (2.6%).

CONCLUSIONS

The use of abciximab as adjunctive therapy in this small group of patients undergoing coronary interventions with high risk of thrombotic complications is associated with high procedural success, but at the expense of high rates of bleeding complications. Therefore, special care must be applied during and after the procedure to enhance the safety of the patients treated with this drug.

Particle Structure and Stability of Colloidal Dispersions as Probed by the Kossel Diffraction Technique

A nondestructive Kossel diffraction technique based on the principle of back-light scattering was used to characterize the structure formation which results from the interparticle interactions in colloidal dispersions. Static structure factors, radial distribution functions, and average pair potentials, which characterize the particle packing structures in model systems of hydroxylate latex dispersions, were obtained. The effects of particle concentration and polydispersity on particle structuring and dispersion stability were also studied. Computer simulations based on the Ornstein-Zernike method were compared with the experimental results. Good quantitative agreement was observed.

[Traumatic aortic valve insufficiency]

The traumatic aortic valvular insufficiency (TAVI), through less frequent after a non-penetrating thoracic traumatism, is a serious entity with a very reserved prognosis. So it must be suspected in every patients with signs or symptoms of de novo heart failure post-traumatism. The transthoracic echocardiography and eventually transesophageal echocardiography have a fundamental role in the confirmation of the diagnosis. The clinical picture of traumatic aortic regurgitation is quickly evolutionary and the non efficacy of medical therapy has placed the valvular substitution surgery as the best succeeded treatment. With the advent of the aortic valve repairing surgery some TAVI cases has been submitted to this procedure. Nevertheless, the development of residual aortic regurgitation in these situations, usually requiring later valvular replacement surgery, make the aortic valvuloplasty a controversial surgical technique. The AA describe a recent clinical case of aortic regurgitation after a non-penetrant thoracic traumatism, discussing the aspects connected with physiopathology, diagnosis and therapy. The singularity of this case was based on the fact that the initial clinical diagnosis had been prejudiced by the context of a polytraumatism and there had been a time free of symptoms between the traumatism and the beginning of the symptomatology of left ventricular failure. Even though the identification of the problem allowed an intensive treatment of this serious situation that ended with the replacement of the aortic valve by mechanical aortic prosthesis, with the patient's total recovery.

[Pacemaker implantation in a patient with persistent left superior vena cava and atresia of the right superior vena cava]

Persistent left superior vena cava with absence or atresia of right superior vena cava is a congenital abnormality of systemic venous return to the heart which may complicate the insertion of a pacemaker electrode. We present a case report of a patient with conduction system disturbances in whom this abnormality was diagnosed during pacemaker implantation, with the possibility of using a transvenous electrode without active fixation system.

[Primary tricuspid valve insufficiency. Report of 2 clinical cases]

Two case reports of primary tricuspid regurgitation are presented which diagnoses were made in mean adult life after a long period of few symptoms. The clinical outcome of the two cases was uneven in the sense that only one of them could be corrected with single surgical procedures. Despite relatively rare, this pathology could probably be turned more frequent with a complete and systematic echocardiographic approach. In connection with the reported cases, a review is made of the main etiologies and of some published reports.

[Myocardial infarct in a young man with normal coronary vessels: apropos of a clinical case treated with streptokinase]

The authors report a case of a 31 year old young man who suffered acute myocardial infarction and was subjected to early treatment with streptokinase. The immediate follow-up showed a complete recanalization of the infarct-related vessel, without any identifiable obstructive lesion on coronary arteriography. Related to this angiographic finding, common in myocardial infarction in the young adult, the authors debate the implicated mechanisms, focusing essentially in the relation endothelium-platelets-vasomotricity. The issue of cigarette smoking as a risk factor and its possible pathogenic implication, even in the absence of atherosclerotic plaque, is also approached.

Distribution of choline acetyltransferase in cerebral and extracerebral cranial arteries of the cat. Its relationship to neurogenic atropine-sensitive dilation

Choline-acetyltransferase (ChAT) activity was surveyed in segments of cranial arteries--both cerebral and extracerebral--from the cat. High levels were found in pial arteries, both cerebral and cerebellar, and in the arteries to salivary glands, tongue, and nose. Intermediate levels were found in the external and internal maxillary arteries and many of their branches. Enzyme levels in the arteries supplying the head--common carotid, vertebral, and in several systemic arteries and veins and also the lingual vein--were probably not significant. Only those vessels that have higher ChAT contents show capacity for neurogenic vasodilation. The dilation of segments of a number of these arteries, the basilar, middle cerebral, lingual, and internal maxillary, is reduced significantly by atropine (5 X 10(-7) M). ChAT activity did not correlate with vessel norepinephrine content. The data may be interpreted as defining a functional vasodilator system to the head encompassing both cerebral and extracerebral arteries that depends in part on a functional cholinergic link involving a muscarinic receptor. It is separate from the adrenergic outflow. The tissues supplied by vasculature receiving this type of innervation are of ectodermal origin.