Irreversible electroporation as treatment of locally advanced and as margin accentuation in borderline resectable pancreatic adenocarcinoma.

In recent years, many local ablation technologies based on thermal damage have been used in the treatment of locally advanced pancreatic carcinoma (LAPC) and borderline resectable pancreatic carcinoma (BLRPC). However, they are associated with major complications because of possible vascular and ductal damage. Irreversible electroporation (IRE) is a nonthermal ablation technology that seems safe near vital vascular and ductal structures. IRE could be used as exclusive treatment of LAPC (en situ to IRE) after induction chemotherapy In BLRPC, surgery is not really radical in 6% of patients (microscopic residual) and local recurrences occur in 11-42% of apparent radical resections. IRE could be used as margin accentuation to increase posterior margin during radical surgery in BLRPC. Our outcomes are safety, time to progression. Secondary outcomes are overall survival, pain control and quality of life. We are performing a prospective evaluation of patients undergoing IRE for LAPC or BLRPC since July 2014. We have included patients with non-metastatic LAPC with maximum size ≤4 cm (en situ to IRE) and patients with BLRPC (complementary IRE). We have performed induction chemotherapy in both groups. After treatment, patients were evaluated on days 1, 2, 4, 7, 14, 21, 30, 60 and 90 with amylase and lipase serum and abdominal drainage test. Based on Ethics Committee's request, follow-up imaging was performed at the 10th day for safety evaluation, at 30, 60 and 90 days for response evaluation and then every 3 months. Seven patients (two women and five men) underwent IRE. Two patients had LAPC and received en situ to IRE. In five patients affected by BLRPC we performed IRE and pancreatic head resection. In all patients, intraoperative imaging confirmed that the treatment of the whole tumor volume was complete. All seven patients demonstrated nonclinically relevant elevation of their amylase and lipase, which returned normal at 5 days postprocedure. No patient showed evidence of clinical pancreatitis or fistula. No major complications were recorded. Patients with LAPC died of distant metastases 6 month after treatment. At 3- and 6-month follow-up, all patients with BLPRC were alive and disease free. Only one patient has already reached 9-month follow-up and is alive and disease free. Our results are only preliminary. However, IRE ablation of LAPC and BLRPC seems a safe and feasible treatment.

Dual MET/EGFR therapy leads to complete response and resistance prevention in a MET-amplified gastroesophageal xenopatient cohort.

Amplification of the MET oncogene occurs in 2-4% of gastroesophageal cancers and defines a small and aggressive subset of tumors. Although in vitro studies have given very promising results, clinical trials with MET inhibitors have been disappointing, showing few and short lasting responses. The aim of the work was to exploit a MET-amplified patient-derived xenograft model to optimize anti-MET therapeutic strategies in gastroesophageal cancer. We found that despite the high MET amplification level (26 gene copies), in the absence of qualitative or quantitative alterations of EGFR, MET inhibitors induced only tumor growth inhibition, whereas dual MET/EGFR inhibition led to complete tumor regression. Importantly, the combo treatment completely prevented the onset of resistance, which quite rapidly appeared in tumors treated with MET monotherapy. We found that this secondary resistance was due to EGFR activation and could be overcome by dual MET/EGFR inhibition. Similar results were also obtained in a MET-addicted, established gastric cancer cell line. In vitro experiments performed on tumor-derived primary cells confirmed that MET inhibitors were not able to abrogate the activation of downstream transducers and that only the combined MET/EGFR treatment completely shut off the signaling. Previously reported cases, as well as those described here, showed only partial and transient sensitivity to anti-MET therapy. The finding that combined anti-MET/EGFR therapy-even in the absence of EGFR genetic alterations-induced complete and durable response, represents a proof of concept and guarantees further investigations, opening a new perspective of treatment for these patients.

The Advanced LIGO photon calibrators.

The two interferometers of the Laser Interferometry Gravitational-wave Observatory (LIGO) recently detected gravitational waves from the mergers of binary black hole systems. Accurate calibration of the output of these detectors was crucial for the observation of these events and the extraction of parameters of the sources. The principal tools used to calibrate the responses of the second-generation (Advanced) LIGO detectors to gravitational waves are systems based on radiation pressure and referred to as photon calibrators. These systems, which were completely redesigned for Advanced LIGO, include several significant upgrades that enable them to meet the calibration requirements of second-generation gravitational wave detectors in the new era of gravitational-wave astronomy. We report on the design, implementation, and operation of these Advanced LIGO photon calibrators that are currently providing fiducial displacements on the order of 10-18m/Hz with accuracy and precision of better than 1%.

[-2]proPSA versus ultrasensitive PSA fluctuations over time in the first year from radical prostatectomy, in an high-risk prostate cancer population: A first report.

BACKGROUND: [-2]proPSA and its derivatives have an higher diagnostic accuracy than PSA in predicting prostate cancer (PCa). In alternative to PSA, ultrasensitive PSA (uPSA) and [-2]proPSA could be potentially useful in recurrent disease detection. This research focused on [-2]proPSA and uPSA fluctuations over time and their possible clinical and pathological determinants, in the first year after RP. METHODS: A cohort of 106 consecutive patients, undergoing RP for high-risk prostate cancer (pT3/pT4 and/or positive margins), was enrolled. No patient received either preoperative/postoperative androgen deprivation therapy or immediate adjuvant RT, this latter for patient choice. [-2]proPSA and uPSA were measured at 1, 3, 6, 9, 12 months after RP; their trends over time were estimated by the mixed-effects linear model. The uPSA relapse was defined either as 3 rising uPSA values after nadir or 2 consecutive uPSA >0.2 ng/ml after RP. RESULTS: The biochemical recurrence (BCR) rate at 1 year after RP was either 38.6 % (in case of 3 rising uPSA values) or 34.9 % (in case of PSA >0.2 ng/ml after nadir), respectively. The main risk factors for uPSA fluctuations over time were PSA at diagnosis >8 ng/ml (p = 0.014), pT (p = 0.038) and pN staging (p = 0.001). In turn, PSA at diagnosis >8 ng/ml (p = 0.012) and pN (p < 0.001) were the main determinants for [-2]proPSA trend over time. In a 39 patients subgroup, uPSA decreased from month 1 to 3, while [-2]proPSA increased in 90 % of them; subsequently, both uPSA and [-2]proPSA increased in almost all cases. The [-2]proPSA trend over time was independent from BCR status either in the whole cohort as well in the 39 men subgroup. CONCLUSIONS: Both uPSA and [-2]proPSA had independent significant fluctuations over time. PSA at diagnosis >8 ng/ml and pathological staging significantly modified both these trends over time. Since BCR was not confirmed as determinant of [-2]proPSA fluctuations, its use as marker of early biochemical relapse may not be actually recommended, in an high-risk prostate cancer patients population.

Treatment of diffuse malignant peritoneal mesothelioma (DMPM) by cytoreductive surgery and HIPEC.

AIM: Diffuse malignant peritoneal mesothelioma (DMPM) is a rare and locally aggressive tumor with poor prognosis, related in most cases to asbestos exposure. It is increasing in frequency, but currently no standard therapy is available. The biology of this disease is still poorly understood. Several highly specialized centers have recently reported improved survival by means of an innovative local-regional approach. The purpose of this article is to evaluate the survival benefit and the morbidity rate of patients affected by DMPM treated at our institution by cytoreductive surgery (CRS) associated with hyperthermic intraperitoneal perioperative chemotherapy (HIPEC). METHODS: This study includes 42 patients affected by DMPM treated by an uniform approach consisting of cytoreductive surgery associated with HIPEC using cisplatin and doxorubicin. The primary end point was overall survival and morbidity rate. The secondary end point was evaluation of prognostic variables for overall survival. RESULTS: The median follow-up period was 72 months (range 1-235 months). Thirty-five patients (83.3%) presented epithelial tumors and 7 were affected by multicystic mesothelioma. The mean peritoneal cancer index (PCI) was 13. Thirty-eight patients (90.4%) had complete cytoreduction (CC-0/1). The overall morbidity rate was 35.7% associated to a perioperative mortality of 7.1%. Median overall survival rate was 65 months with a 1- and 5-year survival rates of 63% and 44%, respectively. CONCLUSION: The treatment of DMPM by CRS+HIPEC in selected patients is a feasible technique that allows to achieve encouraging results in terms of overall survival rate, with an acceptable morbidity rate. Further investigations are needed to clarify the role and the timing of this promising technique.

Treatment of peritoneal carcinomatosis from ovarian cancer by surgical cytoreduction and hyperthermic intraperitoneal chemotherapy (HIPEC).

AIM: Ovarian cancer may be considered as an "intraperitoneal disease" by itself. When surgical removal associated with systemic chemotherapy fails, usually, the history of the patients is characterized by poor prognosis. Some encouraging results have been reported by the treatment of peritoneal carcinomatosis (PC) from ovarian cancer by complete surgical cytoreduction, peritonectomy and hyperthermic intraperitoneal chemotherapy (HIPEC). The purpose of this article was to evaluate the survival benefit and the morbidity of patients with ovarian cancer treated at our institution by cytoreductive surgery associated with hyperthermic intraperitoneal perioperative chemotherapy (HIPEC). METHODS: Between October 1995 and December 2012 more than 600 operations for PC were performed; in 308 cases surgical cytoreduction associated with HIPEC was carried out. Eighty-five patients treated by cytoreduction associated with HIPEC were affected by recurrent epithelial ovarian cancer (EOC). Statistical analysis was performed on 70 patients (last 15 patients were too recent for evaluation). Two trials were applied: 1) patients presenting first peritoneal relapse after surgery and systemic chemotherapy (CT), 6 months later from last CT administration; 2) multiple relapse patients. RESULTS: On 70 patients, morbidity and mortality rates were 35.7% and 7.1%, respectively. Overall median survival was 42.0 months, but in primary EOC was 48.0 months and in recurrent EOC was 28 months (P=0.12). Statistical analysis revealed that the completeness of cytoreduction was the most statistically significant factor related to survival: in completely citoreduced patients, overall survival was 48 months. CONCLUSION: Citoreductive surgery associated to platinum compounds HIPEC is feasible and relatively safe in recurrent and primary PC from ovarian cancer. Better selection of patients and second-look surgery in high risk-patients have to be investigated to improve those encouraging results.

Treatment of peritoneal carcinomatosis from colonic cancer by cytoreduction, peritonectomy and HIPEC: preliminary results in highly selected patients.

AIM: Peritoneal carcinomatosis (PC) is one of the routes of spread of abdominal neoplasms and is generally considered a lethal disease, with a poor prognosis by conventional chemotherapeutic treatments. While systemic chemotherapy has little impact on the treatment of peritoneal disease, some centers have reported encouraging results on overall survival (OS) and disease-free survival (DFS) with surgical cytoreduction associated with hyperthermic intraperitoneal chemotherapy (HIPEC). The purpose of this article is to evaluate the survival benefit and the morbidity in patients affected by colorectal PC treated at our institution by cytoreductive surgery associated with HIPEC. METHODS: In our institution, from October 1995 to June 2012, about 550 operations for PC were performed; in 300 cases cytoreduction plus HIPEC was carried out. Out of 90 operations for colonic cancer: 50 cytoreduction plus HIPEC, 12 cytoreduction and EPIC (early postoperative intraperitoneal chemotherapy) and 28 debulking or explorative laparoscopies/laparotomies were performed. For the present study, 50 patients who had undergone cytoreduction and HIPEC for PC of colorectal cancer origin (CRC) were considered. RESULTS: The morbidity and mortality rates were 34% (17/50) and 2% (1/50), respectively. The patients were divided in two groups according to PCI (peritoneal cancer index, range 0-39) and CC score (completeness of cytoreduction): in Group A (23 patients, PCI>16, CC-2) the median survival time was 15 months compared to 48.1 months for Group B (27 patients, PCI≤16, CC-0/1). The poor survival of Group A seemed to be related to higher PCI and CC score. CONCLUSION: Patient selection based on a maximum PCI of 16 associated with a complete cytoreduction (CC-0) produced encouraging results.

Treatment of pseudomyxoma peritonei with cytoreductive surgery and hyperthermic intraperitoneal chemotherapy (HIPEC): a single center experience.

AIM: Pseudomyxoma peritonei (PMP) is a rare form of peritoneal carcinomatosis characterized by abnormal quantity of extracellular mucinous material. It almost originates from a primary appendiceal tumor with different malignancy degrees. The purpose of this study was to evaluate outcome and long-term survival on 80 patients affected by PMP after cytoreductive surgery (CRS) associated with hyperthermic intraperitoneal chemotherapy (HIPEC). METHODS: From October 1995 to June 2012, about 550 operations for PC were performed; in 300 cases surgical cytoreduction in association with HIPEC was carried out. Regarding PMP, 80 procedures of CRS and HIPEC were performed. This approach is based on surgical removal of the primitive cancer, peritonectomy (stripping of implants on the peritoneal surface) and HIPEC performed with cisplatinum and C mytomicin. The rationale of this treatment is to obtain, after macroscopic disease removal, an elevated and persistent drug concentration in the peritoneal cavity, with limited systemic effects. RESULTS: The complication rate was 52.5% (42/80) with no postoperative deaths. The median overall and progression-free survival were 144 and 88 months, respectively. Not complete cytoreductive surgery (P<0.001), tumor histology (P=0.02) and previous systemic chemotherapy (p = 0.03) were identified in the univariate analysis as independent predictors for a poorer long-term survival. In the multivariate analysis, the completeness of cytoreduction was the only significant variable influencing the outcome. Incomplete cytoreduction (P<0.01) resulted the only statistically significant variable associated with a higher incidence of postoperative complications. CONCLUSION: PMP can be treated with curative intent in a large percentage of cases by cytoreductive surgery associated with HIPEC. This new approach could be performed safely with acceptable morbidity and mortality in selected patients treated in specialized centers. Completeness of cytoreduction allows to achieve the best results.

Myocardial ischaemia in neonates with perinatal asphyxia. Electrocardiographic, echocardiographic and enzymatic correlations.

In asphyxiated neonates, hypoxia is often responsible for myocardial ischaemia. To evaluate cardiac involvement in neonates with respiratory distress, ECG and echocardiographic recordings were performed, and cardiac enzymes determined. These data were related to clinical presentation and patient outcome. Three groups of neonates were studied: 22 healthy newborn infants (group I) with 5 min Apgar scores > 9 and pH > 7.3; 15 neonates with moderate respiratory distress (group II) which had Apgar scores ranging between 7 and 9, and pH between 7.2 and 7.3; and 13 neonates with severe asphyxia, Apgar scores < 7, and pH < 7.2 (group III). The ECGs were evaluated according to the 4-grade classification proposed by Jedeikin et al. [8]. On the echocardiograms, fractional shortening and aortic flow curve parameters were taken into account. Serum creatine kinase (CK), creatine kinase-MB isoenzyme (CK-MB) and lactate dehydrogenase were determined. All of groups I and II survived, but 5 out of 13 in group III died within the 1st week. Grade 3 or 4 ECG changes were observed only in group III patients, while all group II and 3 patients of group I showed grade 2 ECG changes. Fractional shortening, peak aortic velocity and mean acceleration were significantly reduced in group III, whereas the only abnormality found in group II was a reduced fractional shortening. CK, CK-MB, CK-MB/CK ratio and lactate dehydrogenase were all increased in group III, while in group II only CK-MB and the CK-MB/CK ratio were abnormal. Severely asphyxiated newborn infants reflect relevant ischaemic electrocardiographic changes, depressed left ventricular function and marked cardiac enzyme increase. These alterations are far less pronounced in neonates with mild respiratory distress.

Protective effect of poly(ADP-ribose) synthetase inhibition on multiple organ failure after zymosan-induced peritonitis in the rat.

BACKGROUND AND METHODS: In the present study, we tested the hypothesis that peroxynitrite and subsequent activation of the nuclear enzyme poly(ADP-ribose) synthetase (PARS) play a role in the pathogenesis of multiple organ failure induced by peritoneal injection of zymosan in the rat. Animals were randomly divided into six groups (ten rats for each group). The first group was treated with ip administration of saline solution (0.9% NaCl) and served as the sham group. The second group was treated with ip administration of zymosan (500 mg/kg suspended in saline solution). In the third and fourth groups, rats received ip administration of 3-aminobenzamide (10 mg/kg) 1 and 6 hrs after zymosan or saline administration, respectively. In the fifth and sixth groups, rats received ip administration of nicotinamide (50 mg/kg) 1 and 6 hrs after zymosan or saline administration, respectively. After zymosan or saline injection, animals were monitored for 72 hrs to evaluate systemic toxicity (conjunctivitis, ruffled fur, diarrhea, and lethargy), loss of body weight, and mortality. RESULTS: A severe inflammatory response, characterized by peritoneal exudation, high plasma and peritoneal levels of nitrate/nitrite (the breakdown products of nitric oxide), and leukocyte infiltration into peritoneal exudate, was induced by zymosan administration. This inflammatory process coincided with the damage of lung, small intestine, and liver as assessed by histologic examination and by an increase of myeloperoxidase activity, which is indicative of neutrophil infiltration. Zymosan-treated rats showed signs of systemic illness, significant loss of body weight, and high mortality rates. Peritoneal administration of zymosan in the rat also induced a significant increase in the plasma levels of peroxynitrite as measured by the oxidation of the fluorescent dihydrorhodamine 123. Immunohistochemical examination demonstrated a marked increase in the immunoreactivity to nitrotyrosine, a specific "footprint" of peroxynitrite, in the lung of zymosan-shocked rats. In vivo treatment with ip administration of 3-aminobenzamide (10 mg/kg, 1 and 6 hrs after zymosan injection) or nicotinamide (50 mg/kg, 1 and 6 hrs after zymosan injection) significantly decreased mortality, inhibited the development of peritonitis, and reduced peroxynitrite formation. In addition, PARS inhibitors were effective in preventing the development of organ failure because tissue injury and neutrophil infiltration, by myeloperoxidase evaluation, were reduced in the lung, small intestine, and liver. CONCLUSIONS: In conclusion, the major findings of our study are that peroxynitrite and the consequent PARS activation exert a role in the development of multiple organ failure and that PARS inhibition is an effective anti-inflammatory therapeutic tool.

Resistance to PGE2 inhibition of PWM-stimulated lymphocytes from neoplastic patients.

PGE2 treatment of mononuclear cells from patients with different types of neoplasias was unable to decrease either the number of plaque-forming cells or the expression of CD71 and CD25 in PWM-driven cultures. In contrast, in previous studies, PGE2 inhibited these parameters in cultured mononuclear cells from normal volunteers. Surgical treatment of cancer patients did not modify the lymphocyte sensitivity to PGE2 after 1 week, but at 2 and 6 months after therapeutical treatment, the inhibition values of the parameters studied were almost similar or very similar to those of normal lymphocytes. The reduction of PGE2 sensitivity in cancer patients was related to the increase of PGE2 levels and, probably, to a PGE2 receptor saturation. A restoration of PGE2-induced inhibition some months after therapy could be due to the decrease in PGE2 levels and to receptor unsaturation.

Prostaglandin E2 induction of binding activity to CRE and AP-2 elements in human T lymphocytes.

Prostaglandins of the E series are immunomodulatory agents which exert inhibitory as well as stimulatory effects on a variety of immune responses. Since it is known that PGE2 is able to increase cAMP levels, we investigated whether it can affect gene expression through the activation of the transcription factors which bind enhancer elements in the promoter regions of cAMP-regulated genes. Using electrophoretic mobility shift assay, we demonstrated that a short treatment of human T lymphocytes with PGE2 induces specific binding activity to CRE and AP-2, but not AP-1, DNA elements. Since the okadaic acid, a potent protein phosphatase inhibitor, prolongs the induction of the binding activity, phosphorylation events are likely to occur. This activity seems to be due to increased cAMP levels because forskolin and IBMX mimic the effects of PGE2. More interestingly, transfection experiments with CRE-CAT plasmide show that PGE2 activates the transcription of a CRE-containing promoter. These data support the positive role for PGE2 on some immune functions.

PGE2-induced immunoregulation mediated by cytokine production from cultures of human peripheral T lymphocytes.

Prostaglandins (PGs) are generally known to exert inhibitory as well as some enhancing effects on the immune system. This study was performed to assess the influence of the exogenous PGs and cyclic adenosine monophosphate (cAMP)-elevating agents on cytokine production by PWM-stimulated human T lymphocytes. Peripheral blood T lymphocytes from healthy donors were pretreated for 30 min at 25 degrees C with PGE2 (10(-4) to 10(-7) M) PGF1 alpha, IBMX or Forskolin (10(-4) to 10(-5) M) and cultured for 7 days in the presence of Pokeweed Mitogen (PWM), PGE2, IBMX and Forskolin, but not PGF1 alpha, significantly increased IL-6 production while inhibited IL-2, IL-3, IL-4, IFN-gamma, TNF-alpha and GM-CSF production. Our data indicate that cAMP-elevating agents can profoundly affect cytokine secretion by T cells in PWM-driven cultures and that this effect is dose-dependent. The results reported here are compatible with the existence of separate pathways of gene induction for IL-2, IL-3, IL-4, IFN-gamma, TNF-alpha and GM-CSF on the one hand and IL-6 on the other one.

Prostaglandins affect the respiratory burst of human neutrophils.

The effects of prostaglandins on superoxide generation by neutrophils were investigated, since these arachidonic acid metabolites are both involved in the early phase of the inflammatory process and during later stages of neutrophil function. Preincubation of these cells for five minutes with concentrations of PGE2 ranging from 10(-7) to 10(-4) M was able to significantly reduce superoxide production in PMA-stimulated neutrophils. Other pro-inflammatory PGs tested, such as PGE1, PGF1 alpha, PGF2 alpha, inhibited the respiratory burst. The PGE2-induced inhibition was compared to that exerted by staurosporine, a PKC inhibitor. The effects of the two drugs were not additive, since the combinations of PGE2 and staurosporine reduced O2- production to the same extent as staurosporine alone. Possible interferences between PKA- and PKC-mediated transduction signals are discussed.

Intrathecal injection of lysine acetylsalicylic acid in the rat: a neurotoxicological study.

Lysine acetylsalicylic acid has been reported to induce analgesic effects in humans after intrathecal (i.t.) injection. Before conducting further studies in humans with this drug, it is important to evaluate potential toxicological effects on the spinal cord in animals. In the present study the effects of chronic intrathecal administration of provocative doses of lysine acetylsalicylic acid (L-ASA) on the rat spinal cord were evaluated using light and electron microscopy and a quantitative morphometric method. We also investigated the effects of single doses of the drug on the spinal cord blood flow (SCBF) using the laser-Doppler flowmetry technique. No histopathological changes or differences in number or density of neuronal cells could be seen after chronic administration of L-ASA as compared to controls. The SCBF decreased immediately after i.t. injection of a large dose (4 mg) of L-ASA and returned to predrug levels within 10 min. At the end of the experiment metabolic acidosis was detected, indicating a systemic effect of acetylsalicylic acid. It is concluded that no neurotoxic effects on the spinal cord were seen after chronic i.t. injection of L-ASA. From a neurotoxicological point of view, our findings do not contraindicate the spinal use of L-ASA in humans.

Impairment of lymphocyte sensitivity to prostaglandin E2 in cultures from patients with lymphoadenopathy associated syndrome.

Prostaglandin E2 (PGE2) appears to have an immunosuppressive role in human immunodeficiency virus (HIV) infection. Therefore, the effect was studied of PGE2 pretreatment of T lymphocytes from patients with lymphadenopathy associated syndrome (LAS) on the expression of CD25 and CD71 as well as plaque forming cell (PFC) generation in pokeweed mitogen (PWM)-driven cultures. The PGE2-treated or untreated T lymphocytes were cultured with B cells and monocytes in the presence of PWM. Both CD25 and CD71 expression were assessed with an immunofluorescence technique; PFC generation was tested by hemolysis. Before exposure to PWM, LAS lymphocytes showed activation as evidenced by high CD25 and CD71 expression and PFC generation. Pretreatment by PGE2 did not inhibit expression of activation markers and PFC generation in LAS cultures, in contrast to what happened in control cultures. Thus, LAS lymphocytes are activated in vivo and are less sensitive to PGE2 inhibition than normal lymphocytes.

A short incubation with PGE2 affects the proliferative response of T lymphocytes to PWM.

In this study we have investigated the role of PGE2 in the activation of human T lymphocytes by PWM. A preincubation of these cells with molar concentrations of the prostaglandin ranging from 10(-9) M to 10(-4) M is able to reduce the expression of IL-2R and CD71 on T lymphocyte membrane during the first days of culture, while the DR molecule which is expressed later in the same experimental conditions is not affected by the treatment of T lymphocytes with PGE2. The PGE2-induced inhibition of IL-2R and CD71 well correlates with the reduction of 3H-thymidine incorporation by T cells, indicating that a preincubation of T lymphocytes with PGE2 profoundly affects the proliferative apparatus of these cells when they are stimulated by PWM.

Studies on the development of tolerance and potential spinal neurotoxicity after chronic intrathecal carbachol-antinociception in the rat.

The antinociceptive effect in rats produced by chronic intrathecal administration of carbachol was studied for 14 days by the tail immersion test and the paw compression test. Daily injection of 10 micrograms carbachol intrathecally (lumbar level) to 8 rats produced an increase in latency times lasting from day 1 to day 4. The effect was statistically significant during the first 4 days, but not thereafter in both the tail immersion test and the paw compression test as compared to the rats (n = 6) injected with saline. Histopathological examinations of the lumbar spinal cord by light and electron microscopy revealed no signs of neurotoxic reactions of the neurons, nor the spinal tracts. Quantitative morphometric analyses were made by the "disector method", which is an unbiased stereological estimator of cell number and mean cell volume. In the laminae I-III of the L:1 segment, an average number of 88,000 cells/mm3 was found and the mean cell volume was calculated at 560 microns3. Comparison with untreated rats (n = 4) and those injected with saline showed no statistically significant differences. In the present study, the combination of different morphological analyses offers a sensitive method to trace toxic reactions of the nervous tissue. According to these results, intrathecal carbachol produces antinociception, and seems atoxic to spinal nervous tissue, but before intrathecal administration of carbachol to humans is considered, more neurotoxicological data must be obtained.

Behavioral effects after intrathecal administration of cholinergic receptor agonists in the rat.

Behavioral effects of nicotine and cytisine, and the cholinesterase inhibitors physostigmine and 9-amino-1,2,3,4-tetrahydroacridine (THA), administered intrathecally (IT) at the lumbar level in the rat have been evaluated. Antinociceptive dose relationships were established using the tail immersion test. Total activity, locomotion and rearing were also measured in computerized test boxes. The nicotinic receptor antagonist, mecamylamine, and the muscarinic receptor antagonist, atropine, were used to study the selectivity of the effects. Physostigmine and THA significantly decreased total activity, locomotion and rearing as compared to control animals. The motor effects of physostigmine were completely antagonized only partly. Mecamylamine had no antagonistic effect. Nicotine did not affect any activity parameter. Cytisin reduced total activity and locomotion 1-6 min after dose. IT physostigmine, 15 micrograms, increased tail immersion latency for 30 min. No significant increase in response latency in this test was observed after the IT administration of nicotine or THA, whereas cytisine elicited a small increase. The IT administration of THA, nicotine and cytisine was also associated with gnawing, vocalization and hyperactivity and in the case of THA, diarrhoea. These effects were blocked by mecamylamine. Physostigmine antinociception as well as the behavioral effects including total activity, locomotion and rearing caused by physostigmine and by THA are most probably due to an action on spinal muscarinic receptors. Nicotinic receptors do not seem to be involved in spinal antinociception. Some aversive behavioral effects caused by the IT administration of nicotinic receptor agonists could, however, be attenuated by the spinal administration of the antagonist mecamylamine, which may indicate the involvement of nicotinic receptors in afferent sensory transmission.