Long-term follow-up of the randomized trial of mesorectal excision with or without lateral lymph node dissection in rectal cancer (JCOG0212).

BACKGROUND: Japan Clinical Oncology Group (JCOG) 0212 (ClinicalTrials.gov NCT00190541) was a non-inferiority phase III trial of patients with clinical stage II-III rectal cancer without lateral pelvic lymph node enlargement. The trial compared mesorectal excision (ME) with ME and lateral lymph node dissection (LLND), with a primary endpoint of recurrence-free survival (RFS). The planned primary analysis at 5 years failed to confirm the non-inferiority of ME alone compared with ME and LLND. The present study aimed to compare ME alone and ME with LLND using long-term follow-up data from JCOG0212. METHODS: Patients with clinical stage II-III rectal cancer below the peritoneal reflection and no lateral pelvic lymph node enlargement were included in this study. After surgeons confirmed R0 resection by ME, patients were randomized to receive ME alone or ME with LLND. The primary endpoint was RFS. RESULTS: A total of 701 patients from 33 institutions were assigned to ME with LLND (351) or ME alone (350) between June 2003 and August 2010. The 7-year RFS rate was 71.1 per cent for ME with LLND and 70·7 per cent for ME alone (hazard ratio (HR) 1·09, 95 per cent c.i. 0·84 to 1·42; non-inferiority P = 0·064). Subgroup analysis showed improved RFS among patients with clinical stage III disease who underwent ME with LLND compared with ME alone (HR 1·49, 1·02 to 2·17). CONCLUSION: Long-term follow-up data did not support the non-inferiority of ME alone compared with ME and LLND. ME with LLND is recommended for patients with clinical stage III disease, whereas LLND could be omitted in those with clinical stage II tumours.

ANTECEDENTES: El JCOG0212 (ClinicalTrials.gov: NCT00190541) fue un ensayo fase III de no inferioridad en pacientes con cáncer de recto en estadio clínico II/III sin ganglios linfáticos aumentados de tamaño en la pared pélvica lateral. El ensayo comparó la escisión del mesorrecto (mesorectal excision, ME) con la ME con disección de los ganglios linfáticos laterales (lateral lymph node dissection, LLND), siendo el criterio de valoración principal la supervivencia libre de recidiva (recurrence free survival, RFS). El análisis primario planificado a los 5 años de seguimiento no pudo confirmar la no inferioridad de la ME frente a la ME con LLND. Este estudio tuvo como objetivo comparar la ME como procedimiento único y la ME con LLND utilizando datos de seguimiento a largo plazo del ensayo JCOG0212. MÉTODOS: En este estudio se incluyeron pacientes con cáncer de recto en estadio clínico II/III por debajo de la reflexión peritoneal sin ganglios linfáticos aumentados de tamaño en la pared pélvica lateral. Después de que los cirujanos confirmaran la resección R0 mediante la ME, los pacientes fueron asignados al azar al brazo de ME sola o al brazo de ME con LLND. El criterio de valoración principal fue la supervivencia libre de recidiva (RFS). RESULTADOS: Un total de 701 pacientes de 33 instituciones fueron asignados al azar para ser tratados mediante una ME con LLND (n = 351) o EM sola (n = 350) entre junio de 2003 y agosto de 2010. Las tasas de RFS a 7 años fueron del 71,1% para ME con LLND y 70,7 % para ME sola (cociente de riesgos instantáneos, hazard ratio, HR: 1,09 (i.c. del 95% 0,84-1,42), no inferioridad P = 0,064)). El análisis de subgrupos mostró una mejor RFS entre los pacientes en estadio clínico III que se sometieron a ME con LLND en comparación con ME sola (HR: 1,49 (i.c. del 95%: 1,02-2,17)). CONCLUSIÓN: Los datos de seguimiento a largo plazo no justificaron la no inferioridad de la ME en comparación con la ME con LLND. Se recomienda la ME con LLND para pacientes en estadio clínico III, mientras que LLND podría omitirse para pacientes en estadio clínico II.

Male sexual dysfunction after rectal cancer surgery: Results of a randomized trial comparing mesorectal excision with and without lateral lymph node dissection for patients with lower rectal cancer: Japan Clinical Oncology Group Study JCOG0212.

BACKGROUND: We conducted a randomized controlled trial (JCOG0212) to determine whether the outcome of mesorectal excision (ME) alone for rectal cancer is not inferior to that of ME with lateral lymph node dissection (LLND). The present study focused on male sexual dysfunction after surgery. METHODOLOGY: Eligibility criteria included clinical stage II/III rectal cancer, the lower margin of the lesion below the peritoneal reflection, the absence of lateral pelvic lymph node enlargement, and no preoperative radiotherapy. After confirmation of R0 resection by ME, patients were intraoperatively randomized. Questionnaires using the International Index of Erectile Function (IIEF-5) about the sexual function of men were collected before and 1 year after surgery. Sexual dysfunction incidence was defined as the ratio of patients showing sexual dysfunction after surgery relative to the number who had no erectile dysfunction before surgery. RESULTS: Among 701 patients enrolled between June 2003 and August 2010, 472 males were included. Among them, 343 (73%) completed preoperative and postoperative questionnaires. According to the study protocol, the incidences of sexual dysfunction in patients who underwent ME alone and ME with LLND were 68% (17/25; 95%CI, 47-85%) and 79% (23/29; 95%CI, 60-92%), respectively (p = 0.37). Incidences of sexual dysfunction in patients with no or only mild erectile dysfunction before surgery who underwent ME alone and ME with LLND were 59% (48/81) and 71% (67/95), respectively (p = 0.15). Multivariate analysis identified age as the only risk factor for sexual dysfunction after surgery (p = 0.02). CONCLUSIONS: LLND may not increase sexual dysfunction incidence after rectal cancer surgery. This incidence is associated with increased age. This trial is registered with ClinicalTrials.gov, number NCT00190541 and University Hospital Medical Information Network Clinical Trials Registry, number C000000034.

Cecal schwannoma with laparoscopic wedge resection: report of a case.

Schwannomas of the large intestine are relatively rare. Here, we present a case of schwannoma of the cecum in a 59-year-old woman that was successfully resected by laparoscopic wedge resection. In a medical checkup, a colonoscopy revealed a 2 cm submucosal lesion, without mucosal changes, located in the cecum wall contralateral to Bauhin's valve. Abdominal contrast CT and contrast MRI indicated a smooth-surfaced, semi-round tumor of about 2 cm that gave an enhanced homogeneous signal in the cecum. Laparoscopic wedge resection was performed after the diagnosis of benign submucosal tumor. The lesion was 2.5 × 2.0 cm, was histologically composed of spindle neoplastic cells arranged in cords, was positive for S-100 and vimentin, and was diagnosed as schwannoma. The details of this case are reported herein and focus on the successful application of laparoscopic wedge resection for treatment of the colonic submucosal lesion.

Patterns of local recurrence in rectal cancer: a single-center experience.

A cohort of patients operated at the National Cancer Center Hospital in Tokyo for rectal carcinoma, at or below the peritoneal reflection, was reviewed retrospectively. The purpose was to study the risk factors for local relapse and the patterns of local recurrence. Three hundred fifty-one patients operated between 1993 and 2002 for rectal carcinoma, at or below the peritoneal reflection, were analyzed. One hundred forty-five patients, with preoperatively staged T1 or T2 tumors without suspected lymph nodes, underwent total mesorectal excision (TME). Lateral lymph node dissection (LLND) was performed in suspected T3 or T4 disease, or when positive lymph nodes were seen; 73 patients received unilateral LLND and 133 patients received bilateral LLND. Of the 351 patients 6.6% developed local recurrence after 5 years. TME only resulted in 0.8% 5-year local recurrence. In lymph-node-positive patients, 33% of the unilateral LLND group had local relapse, significantly more (p = 0.04) than in the bilateral LLND group with 14% local recurrence. Local recurrence in the lateral, presacral, perineal, and anastomotic subsites was lower in the bilateral LLND group as compared with in the unilateral LLND group. We conclude that, in selected patients, surgery without LLND has a very low local recurrence rate. Bilateral LLND is more effective in reducing the chance of local recurrence than unilateral LLND. Either surgical approach, with or without LLND, requires reliable imaging during work-up.

Diazepam attenuates the post-traumatic hyperactivity of excitatory synapses in rat hippocampal CA1 neurons.

The effect of diazepam, a benzodiazepine derivative, on the post-traumatic hyperactivity of excitatory synaptic transmission was examined in rat hippocampal CA1 area. Optical recordings showed that the activity of hippocampal neurons was enhanced in rats treated with fluid percussion injury (FPI) as compared with that of sham-operated rats. The optical response was characterized by fast and slow components. FPI did not affect the fast component that reflects presynaptic action potentials, but enhanced the slow component that reflects excitatory synaptic responses. Intracellular recordings showed that the amplitude and duration of the excitatory postsynaptic potential (EPSP) were increased after FPI. However, FPI did not affect the resting membrane potential and action potentials of hippocampal neurons. Intraperitoneal (i.p.) administration of diazepam (30 and 90 min after FPI) attenuated the post-traumatic hyperactivity of the slow optical response. The slope of input-to-output relation of excitatory synapses was decreased by acute administration of diazepam to FPI rats, but not by delayed administration of diazepam (4 and 5 h after FPI). The fast optical responses were not affected by either FPI or i.p. administration of diazepam. These results suggest that administration of diazepam at early post-traumatic period prevents the FPI-induced delayed enhancement of excitatory synaptic transmission in rat hippocampal CA1 neurons.

Clinicopathological significance of fibrous tissue around fixed recurrent rectal cancer in the pelvis.

BACKGROUND: Fibrous tissue around a locally recurrent rectal tumour is an interesting histological feature, but its clinicopathological significance has not been investigated. METHODS: This retrospective study examined clinicopathological findings in 48 patients who underwent curative total pelvic exenteration with distal sacrectomy (TPES) between 1992 and 2004. Data were analysed with respect to fibrosis around the recurrent tumour, categorized into one of three groups: no fibrosis (f0), partial fibrosis (f1) or circumferential fibrosis (f2). RESULTS: Ten, 17 and 21 patients had f0, f1 and f2 fibrosis respectively, with 5-year survival of none, four and eight patients respectively. The overall survival of patients with circumferential fibrosis was significantly better than that in patients with no fibrosis (P = 0.003). Univariable analysis showed that a high level of sacrectomy (P = 0.036), absence of lymphatic invasion (P = 0.031) and circumferential fibrosis (P = 0.039) were significantly associated with better overall survival. In multivariable analysis, circumferential fibrosis (P = 0.031) and low serum carcinoembryonic antigen levels (P = 0.044) were independent factors for a favourable outcome. CONCLUSION: The outcome of patients with locally recurrent rectal cancer after curative TPES appears to be better when circumferential fibrosis is present around the tumour.

Clinicopathological significance of microscopic abscess formation at the invasive margin of advanced low rectal cancer.

BACKGROUND: The aim of this study was to evaluate the clinicopathological significance of microscopic abscess formation (MAF) at the invasive front of advanced low rectal cancer. METHODS: The clinicopathological features of 226 consecutive patients with low rectal cancer, who underwent curative resection between May 1997 and December 2002, were analysed. RESULTS: Fifty-seven (25.2 per cent) of the 226 tumours had MAF and 169 (74.8 per cent) did not. Patients with tumours showing MAF were more likely to have extended surgery than those without MAF: 47 versus 31.4 per cent respectively underwent non-sphincter-preserving surgery (P=0.029) and 82 versus 60.9 per cent underwent lateral lymph node dissection (P=0.003). The incidence of lymph node metastases was lower in patients with MAF (30 versus 53.3 per cent; P=0.002). Univariable analysis of disease-free survival revealed that depth of invasion (P<0.001), lymph node status (P<0.001), histological type (P=0.035), lymphatic invasion (P<0.001), venous invasion (P<0.001), perineural invasion (P<0.001), focal dedifferentiation (P<0.001) and MAF (P<0.001) were significant prognostic factors. Multivariable analysis showed that lymph node status (P<0.001), perineural invasion (P=0.002), venous invasion (P=0.033) and MAF (P=0.012) remained independent prognostic factors. CONCLUSION: MAF may reflect indolent tumour behaviour and a more favourable outcome in patients with advanced low rectal cancer.

Reduction of prolonged postoperative hospital stay after laparoscopic surgery for colorectal carcinoma.

BACKGROUND: In evaluating the quality of laparoscopic surgery (LS) for colorectal carcinoma, many previous reports have used median or range values to assess the length of postoperative hospital stay and to show the complication and conversion rates separately. However, with this method, it is impossible to assess the proportion of patients who required prolonged postoperative hospital stay because of perioperative morbidities. This study investigated the proportion of patients who benefited from LS as minimally invasive surgery by assessing the percentage of patients who required prolonged postoperative hospital stay because of major perioperative morbidities. METHODS: A review of 202 patients who underwent LS for colorectal carcinoma at the authors' hospital between January 2002 and December 2004 was performed. Short-term outcomes were compared among the patients who underwent LS in 2002, 2003, and 2004. RESULTS: No significant differences were observed in baseline characteristics among the groups, and all the procedures in this study were completed laparoscopically. There were no significant differences in the operative times and intraoperative blood losses among the groups. Most of the patients resumed liquid intake on postoperative day 1 and solid food on day 3. However, there was a significant difference in the rate of postoperative prolonged hospital stays by year of surgery. In 2004, 97.3% of the patients (72/74) undergoing LS could be discharged to home within 8 days postoperatively. Major complications occurred at a low rate of 1.4% (1/74) in 2004. Regarding the reasons for prolonged postoperative hospital stay, inappropriate judgment of the physician in charge, based primarily on requests from patients without medical necessity, disappeared in 2004. CONCLUSIONS: When LS is performed properly by specialists who have accumulated sufficient experience in both LS and conventional open surgery for colorectal carcinoma, up to 97% of patients undergoing LS can benefit from minimally invasive surgery.

A comparison of the complication rates between laparoscopic colectomy and laparoscopic low anterior resection.

BACKGROUND: This study compared the short-term outcomes, including the complication rate and minimum surgical invasiveness, between patients with colon and rectal carcinomas, who underwent laparoscopic surgery. METHODS: A review evaluated 151 patients who underwent laparoscopic colectomy (Lap-colectomy; n = 120) and laparoscopic low anterior resection (Lap-LAR; n = 31) between July 2001 and December 2003. The short-term outcomes were compared between the two groups. RESULTS: The mean operative time and blood loss were significantly greater in the Lap-LAR group. However, the complication rates and postoperative course between the two approaches were similar, and no anastomotic leakage was observed. There was no significant difference in the serum C-reactive protein level and white blood cell count between the two groups in the early postoperative period. CONCLUSIONS: Lap-LAR for rectal carcinoma can be performed safely without increased morbidity or mortality, and its short-term benefits are comparable with those conferred by Lap-colectomy.

Lateral pelvic lymph node dissection for advanced lower rectal cancer.

BACKGROUND: The oncological outcome of patients who underwent curative surgery for lower rectal cancer was investigated to clarify whether lateral pelvic lymph node dissection (LPLD) conferred any benefit. METHODS: A total of 246 patients who underwent curative surgery for stage II and III lower rectal cancer (below the peritoneal reflection) between 1985 and 1998 was reviewed. Forty-two of these patients did not undergo LPLD. RESULTS: Patients who did not undergo LPLD were older, more likely to have anterior resection and pelvic nerve preservation, and had smaller tumours and lymph node metastasis at an earlier stage than those who underwent LPLD. There was no difference in survival among patients with stage II and III disease between the two groups. However, in patients with pathological N1 lymph node metastasis, the 5-year disease-free survival rate was 73.3 per cent in patients who had LPLD compared with 35.3 per cent among those who did not (P = 0.013). Multivariate analysis showed that LPLD was a significant prognostic factor. CONCLUSION: LPLD improved the prognosis of patients with stage III disease and a small number of lymph node metastases. A randomized clinical trial is needed to verify the benefit of LPLD.

Aggressive surgical treatment for patients with T4 rectal cancer.

OBJECTIVE: To investigate the outcome of surgical treatment for patients with T4 rectal cancer and to evaluate prognostic factors influencing 5-year disease-free survival. PATIENTS: Of 1600 rectal cancers seen between 1985 and 1998, there were 197 patients with T4 of whom 128 were treated with curative intent. In this retrospective study organ invaded, the type of treatment and outcome were analysed. RESULTS: Of the 128 patients, 89% had visceral involvement and 11% had pelvic wall involvement. The most frequently involved organ was bladder, followed by prostate and vagina. Low anterior resection was performed in 52, abdomino-perineal resection in 35 and total pelvic exenteration in 41 patients. Of 81 with urinary tract invasion, 50% were treated with bladder-sparing surgery. Pathological examinations showed bladder involvement in only 44 of these and overall 5-year disease-free survival was 57%. Multivariate analysis revealed that body mass index, lymph node metastasis and inflammatory reaction were significant predictors of survival. CONCLUSION: Completeness of resection is the essential factor influencing oncological outcome.

Development of an aggressive depressed cancer in a case of familial adenomatous polyposis.

In 1977, Kariya et al. reported a case of a small depressed cancer in a patient with familial adenomatous polyposis (FAP) raising the possibility that not all cancers in FAP develop from polypoid adenomas. It is now becoming widely recognized that colonic adenomas may appear as flat or depressed lesions. However, colorectal cancers developing in patients with familial adenomatous polyposis (FAP) are still thought to evolve from adenomatous polyps following the polyp-carcinoma sequence. We report the case of a patient with FAP in whom rectal carcinoma developed 23 years after subtotal colectomy and ileorectal anastomosis. We suggest that this malignancy may have developed de novo because of the depressed shape of the lesion and the aggressive growth pattern. This case raises the possibility that carcinomas may not always evolve from polyps in FAP. Aggressive cancers with a depressed appearance should be searched for when surveying the rectal stump in patients with FAP.

Optical recording of the spatiotemporal propagation of neuronal excitation in the rat hippocampal CA2-CA1 pathway.

Changes in the membrane potential of neurons in the hippocampal CA2 and CA1 regions were recorded by optical recording techniques. After stimulation of the Schaffer collaterals at the hippocampal CA2 region, excitatory optical signals first occurred adjacent stimulus electrode and then flamed-up signals spread toward the hippocampal CA1 region. The optical signal was blocked by tetrodotoxin (TTX) (1 microM). Propagation of the optical signal was blocked in an artificial cerebrospinal fluid (ACSF) containing 0 mM Ca2+ and 6 mM Mg2+. 6,7-Dinitroquinoxaline-2,3 (1H,4H)-dione (DNQX) (20 microM) also blocked the optical signals that spread to the hippocampal CA1 region. The time course of the optical signal recorded at a unit area (49 pixels) on the propagation pathway was characterized by fast and slow components. TTX (1 microM) blocked both fast and slow components of the optical signal. The slow component of the optical signal was preferentially depressed by either removal of external Ca2+ or by bath-application of DNQX (20 microM). When bicuculline (15 microM) was applied to the bath-solution, the intensity and propagation area of the optical signal were increased. The results indicate that stimulation of the Schaffer collaterals in the hippocampal CA2 region produces the propagation of the optical signal to the hippocampal CA1 region, and that the optical signal involves the action potential and excitatory and inhibitory postsynaptic potentials.

Activation of inhibitory pathways suppresses the induction of long-term potentiation in neurons of the rat lateral septal nucleus.

Long-term potentiation of the hippocampal-septal pathway was examined by intracellular recording techniques. High frequency stimulation (two 100-Hz 1-s trains with a 20-s interval between them) of the hippocampal CA3 area resulted in a transient depolarization in rat lateral septal nucleus neurons. High frequency stimulation was followed by a facilitation of fast and slow inhibitory postsynaptic potentials, lasting for more than 2 h, but not by a long-lasting increase in the excitatory postsynaptic potential in the normal solution. Long-term potentiation (>2 h) of the excitatory postsynaptic potential did not appear in 74% of neurons tested, even when the fast inhibitory postsynaptic potential was blocked by bicuculline (30 microM), a GABA(A) receptor antagonist. High frequency stimulation produced long-term potentiation of the excitatory postsynaptic potential in the Mg(2+)-free solution containing bicuculline. When the fast and slow inhibitory postsynaptic potentials were blocked by GABA(A) and GABA(B) receptor antagonists (bicuculline and CGP 55845A respectively), high frequency stimulation produced a large and sustained depolarization followed by long-term potentiation of the excitatory postsynaptic potential. However, the excitatory postsynaptic potential was not enhanced by administration of these drugs after termination of high frequency stimulation. Pretreatment with 2-amino-5-phosphonopentanoate, a NMDA receptor antagonist, resulted in loss of long-term potentiation in both sets of experiments. Paired-pulse stimulation of the hippocampal CA3 region with interstimulus intervals between 200 and 800 ms depressed the second excitatory postsynaptic potential in the presence of bicuculline. CGP 35348, a GABA(B) receptor antagonist, reversed the depression of excitatory postsynaptic potentials to facilitation. These data suggest that high frequency stimulation of hippocampal CA3 neurons enhances the efficacy of GABAergic inhibitory circuits which, in turn, depress the ability of lateral septal nucleus neurons to express long-term potentiation.

Detection of cytokeratin 19 and 20 mRNA in peripheral and mesenteric blood from colorectal cancer patients and their prognosis.

To detect the presence of cancer cells in peripheral and mesenteric blood and to examine their relationship to prognosis in colorectal cancer patients undergoing curative surgery, we examined cytokeratin 19 and 20 mRNA in peripheral and mesenteric venous blood. Using reverse transcriptase polymerase chain reaction, cytokeratin 19 and 20 mRNA was amplified in peripheral and mesenteric blood samples obtained from 35 colorectal cancer patients who underwent curative surgery. Cytokeratin 19 or 20 mRNA in peripheral or mesenteric blood samples was detected in 18 of 35 cases (51%). There was no significant difference in Dukes' staging between the positive and negative groups. The median follow-up period was 56 months. In the positive group six patients (33%) showed recurrences. One patient (6%) showed recurrence in the negative group. The recurrence rate was significantly higher in the positive group than in the negative group. Five-year disease-free survival was significantly better in the negative group than in the positive group (94% vs. 65%). The detection of cytokeratin 19 or 20 mRNA in peripheral or mesenteric blood is thus associated with the prognosis for colorectal cancer patients undergoing curative surgery. Although the presence of these mRNAs in blood samples is a prognostic marker, the clinical utility of this assay is questionable because of the low recurrence rate in the positive group.

5-Hydroxytryptamine facilitates spatiotemporal propagation of optical signals in the hippocampal-septal pathway.

The role of 5-hydroxytryptamine (5-HT) on the propagation of neuronal excitation in the hippocampal-septal pathway was examined in a brain slice by optical and electrophysiological recording techniques. After electrical stimulation of the fimbrial pathway, optical signals first occurred at the caudal region of lateral septal nucleus (LSN), then propagated toward the rostral region of LSN. All of the evoked optical signals were blocked by tetrodotoxin (TTX). The optical signal that propagated to the LSN was blocked by either the removal of external Ca(2+) or bath-application of 6-cyano-7-nitroquinoxaline-2,3-(1H,4H)-dione (CNQX). Bath-application of 5-HT (1-50 microM) to the LSN for 10 min produced an increase in the propagation area of the optical signal and prolonged the falling phase of the optical signal. Bicuculline blocked the 5-HT-induced facilitation of the optical signal. 8-Hydroxy-di-n-propylamino tetralin (8-OH-DPAT), a selective 5-HT(1A) agonist, mimicked the facilitation of 5-HT. 1-(2-Methoxyphenyl)-4-(4-phthalimidobutyl)piperazine (NAN-190), a 5-HT(1A) antagonist, blocked the facilitation induced by 5-HT. 5-HT enhanced the amplitude of the field potential in septal slices, where the optical signals had been enhanced. These results indicate that 5-HT increases the efficacy of excitatory synaptic transmission in the hippocampal-septal circuit via 5-HT(1A) receptors of LSN neurons.

[Surgical treatment of liver metastases from colorectal cancer patient selection and oncological outcome].

The indications for surgical resection of liver metastases from colorectal cancer remain controversial. Clinical, pathological, and outcome data for 418 consecutive patients undergoing hepatectomy between 1984 and 1998 were examined. The over-all 5-year survival rate was 42%, and the 10-year survival rate was 31%. The 5-year survival rate of patients with four or more nodules was 24%, with 20 patients surviving for more than 5 years. Five factors were found to be significant and independent predictors of poor long-term outcome by multivariate analysis. The preoperative scoring system reported by Fong et al was double-checked in our 418 patients and was found to be useful to predict long-term outcome after hepatectomy. It is clear that liver resection alone has limitations. Therefore clinical risk scoring (CRS) and effective intravenous systemic chemotherapy to prevent recurrence both in the remaining liver and lung should be established to improve survival outcome in patients with poor prognostic factors after liver resection.

Characterization of outward currents induced by 5-HT in neurons of rat dorsolateral septal nucleus.

Properties of the 5-hydroxytryptamine (5-HT)-induced current (I(5-HT)) were examined in neurons of rat dorsolateral septal nucleus (DLSN) by using whole cell patch-clamp techniques. I(5-HT) was associated with an increase in the membrane conductance of DLSN neurons. The reversal potential of I(5-HT) was -93 +/- 6 (SE) mV (n = 7) in the artificial cerebrospinal fluid (ACSF) and was changed by 54 mV per decade change in the external K(+) concentration, indicating that I(5-HT) is carried exclusively by K(+). Voltage dependency of the K(+) conductance underlying I(5-HT) was investigated by using current-voltage relationship. I(5-HT) showed a linear I-V relation in 63%, inward rectification in 21%, and outward rectification in 16% of DLSN neurons. (+/-)-8-Hydroxy-dipropylaminotetralin hydrobromide (30 microM), a selective 5-HT(1A) receptor agonist, also produced outward currents with three types of voltage dependency. Ba(2+) (100 microM) blocked the inward rectifier I(5-HT) but not the outward rectifier I(5-HT). In I(5-HT) with linear I-V relation, blockade of the inward rectifier K(+) current by Ba(2+) (100 microM) unmasked the outward rectifier current in DLSN neurons. These results suggest that I(5-HT) with linear I-V relation is the sum of inward rectifier and outward rectifier K(+) currents in DLSN neurons. Intracellular application of guanosine-5'-O-(3-thiotriphosphate) (300 microM) and guanosine-5'-O-(2-thiodiphosphate) (5 mM), blockers of G protein, irreversibly depressed I(5-HT). Protein kinase C (PKC) 19-36 (20 microM), a specific PKC inhibitor, depressed the outward rectifier I(5-HT) but not the inward rectifier I(5-HT). I(5-HT) was depressed by N-ethylmaleimide, which uncouples the G-protein-coupled receptor from pertussis-toxin-sensitive G proteins. H-89 (10 microM) and adenosine 3',5'-cyclic monophosphothioate Rp-isomer (300 microM), protein kinase A inhibitors, did not depress I(5-HT). Phorbol 12-myristate 13-acetate (10 microM), an activator of PKC, produced an outward rectifying K(+) current. These results suggest that both 5-HT-induced inward and outward rectifying currents are mediated by a G protein and that PKC is probably involved in the transduction pathway of the outward rectifying I(5-HT) in DLSN neurons.