Forchlorfenuron-Induced Mitochondrial Respiration Inhibition and Metabolic Shifts in Endometrial Cancer

Forchlorfenuron (FCF) is a widely used plant cytokinin that enhances fruit quality and size in agriculture. It also serves as a crucial pharmacological tool for the inhibition of septins. However, the precise target of FCF has not yet been fully determined. This study reveals a novel target of FCF and elucidates its downstream signaling events. FCF significantly impairs mitochondrial respiration and mediates metabolic shift toward glycolysis, thus making cells more vulnerable to glycolysis inhibition. Interestingly, FCF's impact on mitochondrial function persists, even in cells lacking septins. Furthermore, the impaired mitochondrial function leads to the degradation of HIF-1α, facilitated by increased cellular oxygen. FCF also induces AMPK activation, suppresses Erk1/2 phosphorylation, and reduces the expression of HER2, β-catenin, and PD-L1. Endometrial cancer is characterized by metabolic disorders such as diabetes and aberrant HER2/Ras-Erk1/2/β-catenin signaling. Thus, FCF may hold promise as a potential therapeutic in endometrial cancer.

Vitamin D Receptor Antagonist MeTC7 Inhibits PD-L1

Small-molecule inhibitors of PD-L1 are postulated to control immune evasion in tumors similar to antibodies that target the PD-L1/PD-1 immune checkpoint axis. However, the identity of targetable PD-L1 inducers is required to develop small-molecule PD-L1 inhibitors. In this study, using chromatin immunoprecipitation (ChIP) assay and siRNA, we demonstrate that vitamin D/VDR regulates PD-L1 expression in acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) cells. We have examined whether a VDR antagonist, MeTC7, can inhibit PD-L1. To ensure that MeTC7 inhibits VDR/PD-L1 without off-target effects, we examined competitive inhibition of VDR by MeTC7, utilizing ligand-dependent dimerization of VDR-RXR, RXR-RXR, and VDR-coactivators in a mammalian 2-hybrid (M2H) assay. MeTC7 inhibits VDR selectively, suppresses PD-L1 expression sparing PD-L2, and inhibits the cell viability, clonogenicity, and xenograft growth of AML cells. MeTC7 blocks AML/mesenchymal stem cells (MSCs) adhesion and increases the efferocytotic efficiency of THP-1 AML cells. Additionally, utilizing a syngeneic colorectal cancer model in which VDR/PD-L1 co-upregulation occurs in vivo under radiation therapy (RT), MeTC7 inhibits PD-L1 and enhances intra-tumoral CD8+T cells expressing lymphoid activation antigen-CD69. Taken together, MeTC7 is a promising small-molecule inhibitor of PD-L1 with clinical potential.

Abstract P1-05-35: Identification of Circulating Tumor Cells captured by the FDA Cleared Parsortix® PC1 System from the Peripheral Blood of Metastatic Breast Cancer Patients using Immunofluorescence and Cytopathological Evaluations

Background: Circulating tumor cells (CTCs) captured from the blood of cancer patients may serve as a non-invasive surrogate source of tumor material to investigate tumor characteristics in real-time. The Parsortix® PC1 System, the first FDA-cleared medical device for the capture and harvest of CTCs from peripheral blood of metastatic breast cancer (MBC) patients for use in subsequent user-validated downstream analyses, enables the epitope independent capture of CTCs with diverse phenotypes based on cell size and deformability. In this study, CTCs isolated from the blood of MBC patients by the Parsortix® PC1 System were identified using an immunofluorescence (IF) based assay for detection of epithelial CTCs followed by Wright-Giemsa staining and cytomorphological review. The aim of this study was to determine the proportion of MBC patients and self-declared female healthy volunteers (HVs) that had one or more CTCs identified in the population of cells harvested from their peripheral blood by the Parsortix® PC1 System. Methods: Peripheral blood from 75 HVs and 77 patients with MBC was prospectively collected into K2EDTA tubes at the University of Rochester Medical Center. The blood collected from each subject (8.6±1.2mL) was processed on a Parsortix® PC1 System within 8 hours of collection. The cells harvested by the system were cytospun onto a charged slide and IF stained using an optimised antibody panel. The IF panel consisted of a nuclear dye (DAPI), positive selection markers targeting epithelial CTCs (Cytokeratins (CK) and EpCAM), and negative selection markers targeting white blood cells, such as lymphocytes, macrophages, granulocytes, monocytes, fibroblasts, and cells of megakaryoblastic potential. The stained slides were imaged using fluorescence microscopy and CTCs were defined as nucleated cells (DAPI+) that were positive for CK and/or EpCAM and negative for the blood lineage markers. The IF slides were subsequently stained with Wright-Giemsa and analysed by a qualified pathologist using light microscopy. Morphological features of malignant cells were used to define and identify CTCs. All laboratory testing and analysis was performed by operators blinded to the clinical status of each subject. Results: On the evaluable IF-stained slides, cells classified as CTCs based on their IF staining pattern were identified in 45.3% (34/75) of the MBC patients (range = 0 – 125 CTCs, mean = 7) and in 5.6% (4/71) of the HVs (range = 0 – 8 CTCs, mean = 0). No EpCAM+, CK- CTCs were identified in either MBC patients or HVs. In the 34 MBC patients with one or more CTCs observed, 70.6% had only CK+, EpCAM- cells, while the remaining 29.4% had at least one CK+, EpCAM+ cell. In the HVs, one out of the four CTC-positive donors had only CK+, EpCAM+ cells while the other three had only CK+, EPCAM- cells. On the evaluable Wright-Giemsa stained slides, cells classified as CTCs by the pathologist were identified in 57.1% (40/70) of the MBC patients (range = 0 – 41 CTCs, mean = 4) and in 4.4% (3/68) of the HVs (range = 0 – 14, mean = 0). Conclusions: This study demonstrated the ability of ANGLE’s Parsortix® PC1 System to capture and harvest CTCs from a significantly larger proportion of MBC patients compared to HV subjects. The presence of epithelial cells in subjects without diagnosed disease has been previously described in the literature, with their significance being unclear. This study also demonstrated that the cells harvested by the Parsortix® PC1 System can be successfully evaluated using both IF staining and Wright-Giemsa cytomorphological assessment for the identification of CTCs. Interestingly, a high proportion of the identified CTCs did not express EpCAM, further highlighting the limitations of using EpCAM-based approaches to capture CTCs.

Citation Format: Mariacristina Ciccioli, Richard Moore, Kyu Kwang Kim, Negar Khazan, Michael C. Miller, Anne-Sophie Pailhes-Jimenez. Identification of Circulating Tumor Cells captured by the FDA Cleared Parsortix® PC1 System from the Peripheral Blood of Metastatic Breast Cancer Patients using Immunofluorescence and Cytopathological Evaluations [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P1-05-35.

Abstract P5-06-01: A Multi-center Clinical Study to Harvest and Characterize Circulating Tumor Cells from Patients with Metastatic Breast Cancer Using the Parsortix® PC1 System in support of FDA clearance

Background: Circulating tumor cells (CTCs) captured from the blood of cancer patients may serve as a non-invasive surrogate source of tumor material to investigate tumor characteristics in real-time. However, the only FDA-cleared CTC assay is limited to the enumeration of surface marker-defined epithelial cells and not designed for further characterization of the CTCs identified. The Parsortix® PC1 system is a semi-automated microfluidic device capable of capturing and harvesting CTCs from peripheral blood based on cell size and deformability, making it cell-surface marker agnostic. Here, we demonstrate that the Parsortix® PC1 system enables the enrichment and capture of CTCs from the blood of patients with metastatic breast cancer (MBC) and their interrogation using evaluation techniques commonly available in clinical laboratories. Methods: As part of a multicenter clinical trial (NCT03427450), peripheral blood samples from 216 patients with MBC and 205 healthy volunteers (HVs) were prospectively collected at four different clinical sites located throughout the United States. Each subject provided two separate blood samples collected into K2EDTA Vacutainer® tubes to be processed using the Parsortix® PC1 system on the same day. The cells harvested from one of the blood samples collected from each subject by the Parsortix® PC1 system were deposited onto cytology slides using a cytocentrifugation method and stained with Wright-Giemsa reagents using an automated stainer. The stained slides were subjected to cytopathological evaluation by a board-certified pathologist to enumerate CTCs. As proof of principle, cells harvested from the second blood sample were evaluated using one of three additional techniques: molecular profiling by qRT-PCR, RNA sequencing, or cytogenetic analysis of HER2 amplification by FISH. Results: Cytologic examination identified one or more cells as a CTC in 48.5% (95% CI of 41.5 – 55.4%) of the 194 patients with MBC and 9.9% (95% CI of 6.4 – 14.9%) of the 192 HVs. The results from the qRT-PCR evaluation (102 HVs and 74 MBC patients) showed differential expression of cancer-related genes (KRT19, EPCAM, and TWIST1) in the patients with MBC compared to the HVs. Results from the RNA sequencing (53 HVs and 16 MBC patients) showed differential expression of several genes involved in the Kegg Cancer Pathway in the patients with MBC compared to the HVs. The results from the HER2 FISH evaluation (38 HVs and 101 MBC patients) showed that while the majority of the CTC identified had normal HER2/CEP17 ratios, detection of HER2 amplification was possible. Conclusions: The Parsortix PC1 system is capable of capturing and harvesting CTCs from the peripheral blood of patients with MBC. Harvested cells can be evaluated using standard orthogonal methodologies such as gene expression and FISH to identify and characterize CTCs. Based in part on the above results, the FDA granted a De Novo classification request (DEN200062) for the Parsortix PC1 device in May of 2022.

Citation Format: Evan Cohen, Gitanjali Jayachandran, Richard Moore, Massimo Cristofanilli, Julie E. Lang, Joseph Khoury, Michael F. Press, Heather McBride, Kyu Kwang Kim, Negar Khazan, Qiang Zhang, Youbin Zhang, Roberta Guzman, Michael C. Miller, James Reuben, Naoto T. Ueno. A Multi-center Clinical Study to Harvest and Characterize Circulating Tumor Cells from Patients with Metastatic Breast Cancer Using the Parsortix® PC1 System in support of FDA clearance [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P5-06-01.

Analytical performance of the FDA-cleared Parsortix® PC1 system

Introduction

The Parsortix® PC1 system, Food and Drug Administration (FDA) cleared for use in metastatic breast cancer (MBC) patients, is an epitope-independent microfluidic device for the capture and harvest of circulating tumor cells from whole blood based on cell size and deformability. This report details the analytical characterization of linearity, detection limit, precision, and reproducibility for this device.

Methods

System performance was determined using K2-EDTA blood samples collected from self-declared healthy female volunteers (HVs) and MBC patients spiked with prelabeled cultured breast cancer cell lines (SKBR3, MCF7, or Hs578T). Samples were processed on Parsortix® PC1 systems and captured cells were harvested and enumerated.

Results

The system captured and harvested live SKBR3, MCF7, and Hs578T cells and fixed SKBR3 cells linearly between 2 and ~100 cells, with average harvest rates of 69%, 73%, 79%, and 90%, respectively. To harvest ≥1 cell ≥95% of the time, the system required 3, 5 or 4 live SKBR3, MCF7 or Hs578T cells, respectively. Average harvest rates from precision studies using 5, 10, and ~50 live cells spiked into blood for each cell line ranged from 63.5% to 76.2%, with repeatability and reproducibility percent coefficient of variation (%CV) estimates ranging from 12.3% to 32.4% and 13.3% to 34.1%, respectively. Average harvest rates using ~20 fixed SKBR3 cells spiked into HV and MBC patient blood samples were 75.0% ± 16.1% (%CV = 22.3%) and 68.4% ± 14.3% (%CV = 21.1%), respectively.

Conclusions

These evaluations demonstrate the Parsortix® PC1 system linearly and reproducibly harvests tumor cells from blood over a range of 1 to ~100 cells.

A Multi-Center Clinical Study to Harvest and Characterize Circulating Tumor Cells from Patients with Metastatic Breast Cancer Using the Parsortix® PC1 System

Circulating tumor cells (CTCs) captured from the blood of cancer patients may serve as a surrogate source of tumor material that can be obtained via a venipuncture (also known as a liquid biopsy) and used to better understand tumor characteristics. However, the only FDA-cleared CTC assay has been limited to the enumeration of surface marker-defined cells and not further characterization of the CTCs. In this study, we tested the ability of a semi-automated device capable of capturing and harvesting CTCs from peripheral blood based on cell size and deformability, agnostic of cell-surface markers (the Parsortix® PC1 System), to yield CTCs for evaluation by downstream techniques commonly available in clinical laboratories. The data generated from this study were used to support a De Novo request (DEN200062) for the classification of this device, which the FDA recently granted. As part of a multicenter clinical trial, peripheral blood samples from 216 patients with metastatic breast cancer (MBC) and 205 healthy volunteers were subjected to CTC enrichment. A board-certified pathologist enumerated the CTCs from each participant by cytologic evaluation of Wright-Giemsa-stained slides. As proof of principle, cells harvested from a concurrent parallel sample provided by each participant were evaluated using one of three additional evaluation techniques: molecular profiling by qRT-PCR, RNA sequencing, or cytogenetic analysis of HER2 amplification by FISH. The study demonstrated that the Parsortix® PC1 System can effectively capture and harvest CTCs from the peripheral blood of MBC patients and that the harvested cells can be evaluated using orthogonal methodologies such as gene expression and/or Fluorescence In Situ Hybridization (FISH).

Identification of a Vitamin-D Receptor Antagonist, MeTC7, which Inhibits the Growth of Xenograft and Transgenic Tumors In Vivo

Vitamin-D receptor (VDR) mRNA is overexpressed in neuroblastoma and carcinomas of lung, pancreas, and ovaries and predicts poor prognoses. VDR antagonists may be able to inhibit tumors that overexpress VDR. However, the current antagonists are arduous to synthesize and are only partial antagonists, limiting their use. Here, we show that the VDR antagonist MeTC7 (5), which can be synthesized from 7-dehydrocholesterol (6) in two steps, inhibits VDR selectively, suppresses the viability of cancer cell-lines, and reduces the growth of the spontaneous transgenic TH-MYCN neuroblastoma and xenografts in vivo. The VDR selectivity of 5 against RXRα and PPAR-γ was confirmed, and docking studies using VDR-LBD indicated that 5 induces major changes in the binding motifs, which potentially result in VDR antagonistic effects. These data highlight the therapeutic benefits of targeting VDR for the treatment of malignancies and demonstrate the creation of selective VDR antagonists that are easy to synthesize.

HE4 Overexpression by Ovarian Cancer Promotes a Suppressive Tumor Immune Microenvironment and Enhanced Tumor and Macrophage PD-L1 Expression

Ovarian cancer is a highly fatal malignancy characterized by early chemotherapy responsiveness but the eventual development of resistance. Immune targeting therapies are changing treatment paradigms for numerous cancer types but have had minimal success in ovarian cancer. Through retrospective patient sample analysis, we have determined that high human epididymis protein 4 (HE4) production correlates with multiple markers of immune suppression in ovarian cancer, including lower CD8⁺ T cell infiltration, higher PD-L1 expression, and an increase in the peripheral monocyte to lymphocyte ratio. To further understand the impact that HE4 has on the immune microenvironment in ovarian cancer, we injected rats with syngeneic HE4 high- and low-expressing cancer cells and analyzed the differences in their tumor and ascites immune milieu. We found that high tumoral HE4 expression promotes an ascites cytokine profile that is rich in myeloid-recruiting and differentiation factors, with an influx of M2 macrophages and increased arginase 1 production. Additionally, CTL activation is significantly reduced in the ascites fluid, and there is a trend toward lower CTL infiltration of the tumor, whereas NK cell recruitment to the ascites and tumor is also reduced. PD-L1 expression by tumor cells and macrophages is increased by HE4 through a novel posttranscriptional mechanism. Our data have identified HE4 as a mediator of tumor-immune suppression in ovarian cancer, highlighting this molecule as a potential therapeutic target for the treatment of this devastating disease.

Novel Small Molecule MEK Inhibitor URML-3881 Enhances Cisplatin Sensitivity in Clear Cell Ovarian Cancer

Advanced clear cell ovarian cancer (CCOC) is a highly fatal malignancy with a scarcity of effective treatment options. CCOC is inherently chemotherapy resistance, but the exact mechanism of this resistance has yet to be established. Prosurvival signaling, such as through the MAPK cascade, is one way in which cancer cells can evade chemotherapy. We have determined that CCOC exhibits baseline elevated levels of MAPK activity, which increase further upon cisplatin exposure. We have developed a novel MEK inhibitor, URML-3881, to test the effect of MAPK inhibition in CCOC. URML-3881 was found to reduce in vitro CCOC viability through apoptosis and proliferation inhibition, yet it failed to induce in vivo tumor regression. Similarly, cisplatin alone had minimal impact on tumor growth, but remarkably, the combination of MEK inhibition and cisplatin led to a significant and prolonged tumor regression. These studies confirm that the combination of MEK inhibition with URML-3881 and cisplatin is superior to either agent alone in CCOC. Our data support the design of future preclinical and clinical studies into the combination of MEK inhibition and platinum-based chemotherapy as a treatment strategy for CCOC.

Haloperidol pretreatment unmasks the kappa opioid effects of U-50, 488H on cortical EEG and EEG power spectra in rats

Adult female Sprague-Dawley rats were implanted with chronic cortical EEG electrodes and intravenous cannulae. U-50, 488H injection (5.0 mg/kg) produced initial EEG desynchrony and EEG spectral power that was mainly distributed over the zero to 10 Hz range, including a relatively small spectral peak in the 4-6 Hz band. In contrast, following haloperidol pretreatment (0.1 mg/kg), U-50, 488H injection produced high-voltage EEG bursts and a predominant EEG spectral peak in the 4-6 Hz band. These effects of U-50, 488H after haloperidol pretreatment were identical to those previously demonstrated with the benzomorphan kappa agonist ethylketocyclazocine. Thus, haloperidol pretreatment unmasked the kappa opioid effects of U-50, 488H.

Modulation of morphine-induced EEG and behavioral effects by dynorphin A-(1-13) in non-tolerant and morphine-tolerant rats

The purpose of the present study was to assess effects of dynorphin A-(1-13) on morphine-induced changes in electroencephalographic (EEG) spectral power and morphine-induced suppression of slow-wave sleep in non-tolerant and morphine-tolerant rats. Adult female Sprague-Dawley rats were implanted with chronic cortical EEG electrodes, electromyographic electrodes in the temporalis muscle and with intracerebroventricular (i.c.v.) cannulae and, in some cases, additional intravenous (i.v.) cannulae. Injections of morphine (i.c.v., 20 micrograms/rat) produced a biphasic EEG and behavioral response, composed of 2-3 hr of slow-wave bursts and increased spectral power (0-4 Hz) in the EEG, associated with behavioral stupor, followed by 2-3 hr of EEG and behavioral arousal. Dynorphin (i.c.v., 20 micrograms/rat), administered 10 min before injections of morphine in non-tolerant rats, antagonized morphine-induced increases in spectral power of the EEG and morphine-induced suppression of slow-wave sleep. In addition, EEG power spectra obtained after intraventricular administration of morphine from rats, treated with dynorphin and morphine intraventricularly 24 hr earlier, were qualitatively similar to those previously found after acute administration of kappa opioid agonists. In morphine-tolerant rats, pretreatment with dynorphin given intraventricularly, 10 min prior to intraventricular administration of morphine, restored morphine-induced increases in EEG spectral power and suppression of slow-wave sleep. The results suggest that dynorphin may modulate the characteristics of opioid receptors.

Dissociation of the opioid and nonopioid effects of cyclazocine

Lower IV doses of (dl)- and (l)-cyclazocine (0.05 and 0.50 mg/kg) in the rat produced opioid EEG and behavioral effects that were antagonized by naltrexone pretreatment. Higher IV doses of (dl)- and (l)-cyclazocine (1.00 and 2.00 mg/kg) produced initial "psychotomimetic-like" behavioral effects that were naltrexone-resistant, followed by the delayed emergence of opioid EEG and behavioral effects that were naltrexone-sensitive, (d)-Cyclazocine produced only "psychotomimetic-like" behavioral effects that were naltrexone-resistant. (dl)-Cyclazocine antagonized morphine-induced EEG and behavioral effects in naive rats. (l)-Cyclazocine precipitated withdrawal symptoms in morphine-dependent rats. In contrast, (d)-cyclazocine produced "psychotomimetic-like" effects, but no withdrawal symptoms. Thus, (dl)- and (l)-cyclazocine produced dose- and time-related opioid and nonopioid "psychotomimetic-like" effects, while (d)-cyclazocine produced only nonopioid "psychotomimetic-like" effects.

Opioid self-administration in rats: pharmacodynamics and pharmacokinetics

This article provides comparative data obtained during opioid self-administration in rats, using our EEG-EMG rat model of addiction. This model allows continuous recording of EEG and EMG activities and programming of intravenous drug injections. Comparative data on opioid self-administration patterns are presented. These studies on the association between EEG and behavioral correlates of opioid self-administration have contributed to the delineation of similarities and differences in pharmacodynamic and pharmacokinetic characteristics of opioids.

Differential tolerance to repeated daily injections of N-allylnormetazocine and its enantiomers in the rat

This study was designed to compare the development of tolerance to the effects of N-allylnormetazocine (SKF-10,047) and its enantiomers on the EEG and on behavior. Adult female Sprague-Dawley rats were implanted with chronic cortical electroencephalogram (EEG) and electromyogram (EMG) recording electrodes in the temporalis muscle and with permanent cannulae in the external jugular vein. In non-tolerant rats, 10 mg/kg (i.v.) injections of SKF-10,047 racemate produced primarily aroused wakefulness for about 120 min, that was associated with alternation between desynchronized EEG and theta waves in the EEG. After these rats received a series of automatic, intravenous injections of SKF-10,047 racemate, the aroused wakefulness state induced by SKF-10,047 racemate lasted for about 40 min. In non-tolerant rats, 2.5 mg/kg (i.v.) injections of (+)-SKF-10,047 induced a psychotomimetric EEG and behavioral state for about 30 min, which included continuous theta wave activity in the EEG. After chronic treatment with (+)-SKF-10,047, the psychotomimetic state induced by (+)-SKF-10,047 persisted for about 20 min. In non-tolerant rats, 2.5 mg/kg (i.v.) injections of (-)-SKF-10,047 produced an aroused EEG and behavioral wakefulness for about 30 min, which was then followed by slow-wave bursts in the EEG and associated behavioral stupor for about 90 min. After chronic treatment with (-)-SKF-10,047, injection of (-)-SKF-10,047 produced predominantly aroused wakefulness for about 45 min. The data suggest that (+)-SKF-10,047 exerts psychotogenic properties, but not opioid properties. On the other hand, the data suggest that (-)-SKF-10,047 possesses opioid properties.

Intracerebroventricular morphine produces diuresis 24 h after previous dynorphin/morphine treatment

The effect of dynorphin A-(1-13) on morphine-induced urine output was studied in the rat. The previous simultaneous intracerebroventricular (i.c.v.) injection of dynorphin (20 micrograms/rat) and morphine (20 micrograms/rat) altered the response of rat given morphine (20 micrograms/rat) 24 h later, producing a 3-fold increase in urine output. In contrast, previous injection of dynorphin or morphine alone had no effect.

Bidirectional cross-tolerance between methadone (mu)- and ethylketocyclazocine (kappa)-tolerant rats

Our laboratory previously reported on unidirectional cross-tolerance between morphine and methadone, both mu opioid agonists, and between morphine and ethylketocyclazocine (EKC), the latter being a relatively selective kappa opioid agonist. Morphine-tolerant rats were found to be non-cross-tolerant to methadone and EKC, but methadone- and EKC-tolerant rats were cross tolerant to morphine. In the present study, we characterized the cross-tolerance between methadone and EKC. A group of female adult Sprague-Dawley rats was made tolerant to methadone by a series of automatic i.v. injections ranging from 0.25 mg/kg per 2 h on the first day to 2.0 mg/kg per 1.5 h on the ninth day. Another group of rats was similarly made tolerant to EKC with doses ranging from 0.5 mg/kg per 2 h on the first day to 4 mg/kg per h on the ninth day. Relatively similar degrees of tolerance development to the EEG and behavioral effects of methadone and EKC were reflected by decreases in durations of action and decreases in opioid-induced EEG power spectral changes. Methadone-tolerant rats were found to be cross-tolerant to the EEG and behavioral effects of EKC, and, similarly, EKC-tolerant rats were found to be cross-tolerant to those of methadone. Thus, a bidirectional cross-tolerance between a mu and a kappa agonist was demonstrated. The present results together with those reported earlier indicate that cross-tolerance may not be directly related to the receptor selectivity of the opioids. It is possible that differential physicochemical properties of these opioids may play a more decisive role in the phenomenon of cross-tolerance.

Differential protracted effects of morphine and ethylketocyclazocine challenges on EEG and behavior in the rat

One group of six adult female Sprague-Dawley rats was given a series of automatically administered i.v. morphine injections over eight days. Similarly, a second group of six rats was given ethylketocyclazocine (EKC). Control rats received chronic i.v. saline injections. Tolerance to EEG and behavioral effects of morphine and EKC was demonstrated. At 15 days morphine post-withdrawal, morphine challenges produced EEG and behavioral stupor for a mean of 5 min, followed by EEG and behavioral arousal for a mean of 131 min. In contrast, morphine challenges in saline control rats produced a biphasic EEG and behavioral response consisting of a mean of 85 min of stupor, followed by a mean of 88 min of arousal. However, at 15 days EKC post-withdrawal, EKC challenges produced a biphasic EEG and behavioral response consisting of a mean of 57 min of depression followed by a mean of 55 min of arousal; control saline rats demonstrated similar responses to EKC challenges. Similar results were obtained at one month post-withdrawal for all groups. Thus, protracted effects on EEG and behavior were evident in rats chronically treated with morphine, but not in rats chronically treated with EKC.

Tremor at rest episodes in unilaterally 6-OHDA-induced substantia nigra lesioned rats: EEG-EMG and behavior

Twenty male adult Wistar rats were unilaterally lesioned in the substantia nigra (SN) with 6-hydroxydopamine (6-OHDA), and prepared with chronic cortical (ECoG) and neck muscle (EMG) electrodes. Longitudinal study over a period of up to 18 months demonstrated the emergence, in about two-thirds of the rats, of spontaneous repetitive episodes of head and neck tremor during awake at rest, of up to 20 seconds duration each, that were associated with spike and wave-like ECoG activities. These episodes of tremor at rest disappeared during sleep and REM sleep episodes, and also following the i.p. administration of L-DOPA. It is assumed that these tremor at rest episodes are analogous to those reported to occur in primates after experimentally induced dysfunction of the nigro-striatal, extrapyramidal system.

Suppression of PCP-induced behavioral arousal in the rat by yohimbine pretreatment

The ability of yohimbine pretreatment to block PCP-induced increases in general motor behavior and head bobbing was assessed in adult female Sprague-Dawley rats. PCP-induced (5 mg/kg i.p.) increases in motor activity were significantly antagonized by yohimbine (5 mg/kg i.p.). More specific PCP-induced (5 mg/kg i.v.) head bobbing was antagonized in a dose-related manner by yohimbine (2.5 and 5 mg/kg i.p.). These data may lead to a better understanding of the mode of action of PCP.

Comparison of abstinence syndromes following chronic administration of mu and kappa opioid agonists in the rat

Abstinent states were compared following chronic administration of mu and kappa opioid agonists, morphine and ethylketocyclazocine, respectively. Rats were prepared with chronic EEG and EMG electrodes and indwelling IV cannulae. One group of rats was chronically administered IV morphine, while a second group received chronic injections of IV ethylketocyclazocine. Morphine abstinence was associated with suppression of REM sleep occurrences, increases in number of wet-dog shakes, and a decline in EEG spectral power during slow-wave sleep episodes. In contrast, the ethylketocyclazocine abstinence syndrome included minor abstinence signs. Differences in abstinent states between morphine and ethylketocyclazocine indicate the involvement of separate receptor populations in the process of dependence on morphine and ethylketocyclazocine.

Sigma opioid receptors; SKF-10,047 update

We found that (-)-SKF-10,047 blocks EEG and behavioral effects of morphine in the naive rat, precipitates withdrawal in morphine-dependent rats, produces physical dependence as evidenced by naloxone-induced withdrawal, and displaces [3H] dihydromorphine from brain homogenates. (+)-SKF-10,047 did not produce dependence upon chronic treatment, and it did not displace [3H] dihydromorphine from brain homogenates. Such pharmacodynamic dissociation of SKF-10,047 effects suggests an association of sigma receptors with psychotogenic, but not opioid characteristics. The latter are most likely mediated by mu or kappa receptors.

Differential neuropharmacological effects of mu, kappa and sigma opioid agonists on cortical EEG power spectra in the rat. Stereospecificity and naloxone antagonism

The study was designed to determine and compare the acute effects of the enantiomers of mu, kappa and sigma opioid agonists on the cortical EEG with the spectral analysis technique. The relative ability of naloxone to antagonize such effects was also assessed. Adult female Sprague-Dawley rats were implanted with chronic cortical EEG and temporalis muscle EMG recording electrodes, and with permanent indwelling external jugular cannulae. (-)-Methadone(mu agonist) produced increases in spectral power over the zero to 10Hz range, while (-)-ketocyclazocine (kappa agonist) produced increases in the 5-8 Hz band as a predominant peak. The(+) enantiomers of methadone and ketocyclazocine were inactive. The drug (+)-SK-10,047 (sigma agonist), produced a predominant spectral peak in the 7-9 HZ band that was associated with behavior that suggested psychotomimetic effects. The effects of morphine (mu agonist) on EEG and EEG power spectra were more sensitive to antagonism by naloxone than those produced by ketocyclazocine. The effects of (+/-)-SKF-10,047 and (+)-SKF-10,047 were not antagonized by 10 mg/kg of naloxone, while the effects of (-)-SKF-10,047 were partially antagonized by 10 mg/kg of naloxone. These findings further delineate the specificity of the differential effects of mu, kappa and sigma opioid agonists on the EEG and EEg power spectra in the rat.

Sigma receptors mediated the psychotomimetic effects of N-allylnormetazocine (SKF-10,047), but not its opioid agonistic-antagonistic properties

Our present findings suggest that SKF-10,047, the prototype sigma agonist, has its opioid entity residing with its (-) isomer, while both its (+) and (-) isomers possess psychotogenic properties similar to those produced by PCP. We found that (-)-SKF-10,047 blocks EEG and behavioral effects of morphine in the naive rat, precipitates withdrawal in morphine-dependent rats, produces physical dependence as evidenced by naloxone-induced withdrawal, and displaces [3H]dihydromorphine from brain homogenates. (+)-SKF-10,047 did not produce dependence upon chronic treatment, and it did not displace [3H]dihydromorphine from brain homogenates. Such pharmacodynamic dissociation with SKF-10,047 suggests an association of sigma receptors with psychogenic, but not opioid effects. The latter are most likely mediated by mu or kappa receptors.

Differential tolerance and cross-tolerance to repeated daily injections of mu and kappa opioid agonists in the rat

This study was designed to compare the development of tolerance to the effects of morphine and ethylketocyclazocine ( EKC ) on EEG, EEG power spectra and behavior and to assess any cross-tolerance. Adult female Sprague-Dawley rats were implanted with chronic cortical EEG and temporalis muscle EMG recording electrodes and with permanent cannulae in the external jugular vein. In non-tolerant rats, 10 mg/kg (i.v.) injections of morphine and of ethylketocyclazocine produced biphasic EEG and behavioral profiles lasting for 3 and 2 hr , respectively. In both cases, a stuporous phase, associated with high-voltage cortical EEG bursts, was followed by a hyperactive phase, associated with low-voltage desynchronized EEG. However, power spectra derived from epochs of EEG bursting produced by morphine and ethylketocyclazocine were qualitatively different. One group of rats was then given a series of automatic, intravenous injections of morphine, while a second group received ethylketocyclazocine. Following chronic treatment, the duration of the biphasic EEG and behavioral profiles induced by morphine and ethylketocyclazocine were both significantly reduced. In both cases, the intensity of EEG bursting was also reduced as reflected by significant quantitative reductions in EEG power spectral densities. In assessments of cross-tolerance, ethylketocyclazocine tolerant rats were found to be cross-tolerant to the effects of morphine. However, no cross-tolerance to the effects of ethylketocyclazocine in morphine-tolerant rats was observed. These data contribute to a further understanding of the relative heterogeneity of mu and kappa receptor populations and to the differential pharmacodynamics of morphine and ethylketocyclazocine.

Self-administration of ketocyclazocine and ethylketocyclazocine by the rat

The purpose of the study was to assess possible substitution of either ketocyclazocine or ethylketocyclazocine for morphine in rats maintaining their own dependence by self-administration. Rats were prepared with indwelling IV cannulae, made tolerant to and physically dependent on morphine, then trained to lever press for morphine self-injections on a fixed ratio (FR) schedule of reinforcement. When either ketocyclazocine or ethylketocyclazocine was substituted for morphine, rats self-administered single injections of these kappa opioid agonists at relatively evenly spaced intervals over a 24-hr period. These self-injection patterns continued for up to at least 15 consecutive days. Substitution of saline for the kappa opioid agonists did not result in the emergence of a morphine-like abstinence syndrome. Differences in extent and intensity of withdrawal between morphine and these kappa opioid agonists indicate the involvement of separate receptor populations in the process of dependence on morphine and these kappa opioid agonists.

Electromyographic power spectral changes associated with the sleep-awake cycle and with diazepam treatment in the rat

Power spectral analysis was used to study temporalis muscle EMG activities during the sleep-awake cycle in the rat. EMG spectra derived from EMG during the states of slow-wave sleep. REM sleep and wakefulness demonstrated qualitative and quantitative differences. Diazepam treatment produced reductions in EMG spectral power during wakefulness. Thus, our experimental model allows qualitative and quantitative delineation of EMG activity associated with behavioral changes or drug treatments.

Self-administration of dynorphin-[1-13] and D-ala2-dynorphin-[1-11] (kappa opioid agonists) in morphine (mu opioid agonist)-dependent rats

Adult female Sprague-Dawley rats were prepared with permanent cortical EEG and temporalis EMG electrodes and i.v. cannulae. They were made tolerant to and physically dependent on morphine by automatic, hourly injections. These physically dependent rats were then trained to lever press for 10 mg/kg injections of morphine on a fixed ratio (FR) schedule of reinforcement. Upon stabilization of morphine self-administration at a FR-10, dynorphin-[1-13] (DYN) or D-ala2-dynorphin-[1-11] (D-ala2-DYN) at doses of 125 or 250 micrograms/kg/inj was substituted for morphine. Rats self-administered these opioid-like peptides at both dose levels. As expected, self-injections were more numerous at the lower dose. No signs of morphine withdrawal were seen during the peptide substitutions. Following DYN or D-ala2-DYN abstinence, no withdrawal symptoms were noted. The question is raised as to whether DYN or D-ala2-DYN and morphine are producing their reinforcing effects in sustaining self-administration via the same receptor populations. Since morphine abstinence is associated with severe withdrawal symptoms and the peptides studied are not, the involvement of separate receptor populations in the process of dependence on morphine and these opioid-like peptides is indicated. In conclusion, both a mu and two kappa agonists exhibited an analogous reinforcing property in the rat. However, the degree of physical dependence and the intensity of withdrawal differed; being higher with the mu agonist and lower with the kappa agonists.

Effects of acute delta 9-THC administration on EEG and EEG power spectra in the rat

This study was designed to determine the acute effects of delta 9-THC on the cortical EEG with the spectral analysis technique. Adult female Sprague-Dawley rats were implanted with chronic cortical and temporalis muscle electrodes. Intraperitoneally administered delta 9-THC (5 and 10 mg/kg) produced a reduction in peak-to-peak voltage of the desynchronized cortical EEG during wakefulness. Associated spectral power was reduced to about 50% of control during the first hour after injection of delta 9-THC and gradually returned toward the control value over an 8-hr period. Occurrences of delta 9-THC-induced high-voltage EEG bursts, overriding the reduced EEG tracing, were associated with an EEG spectral peak at 6 Hz. The first few slow-wave sleep (SWS) episodes appearing after delta 9-THC administration were associated with more slow-frequency waveforms and more slow-frequency spectral power than with control slow-wave sleep episodes. During control rapid eye movement (REM) sleep episodes, an EEG theta wave pattern, with an associated spectral peak at about 8 Hz, was characteristic. Conversely, the first few REM sleep episodes emerging after delta 9-THC administration contained overriding high-voltage bursts, the related power spectra of which had two peaks at about 7 and 11 Hz.

Relationships between blood ethanol levels and ethanol-induced changes in cortical EEG power spectra in the rat

Adult female Sprague-Dawley rats were implanted with chronic cortical and temporalis muscle electrodes and/or intravenous cannulas. After acute ethanol administration, dose-dependent linear declines in blood ethanol concentration were found. Ethanol-induced increases in EEG spectral power in the 0 - 4 Hz band persisted long after blood ethanol levels and declined to zero; therefore, we found no correlation. Acute ethanol administration also produced an initial drop in 8 - 13 Hz spectral power. Then, as blood ethanol levels declined, 8 - 13 Hz spectral power increased toward normal; a significant negative linear correlation was found.

Self-administration of nalbuphine, butorphanol and pentazocine by morphine post-addict rats

The purpose of the study was to define possible self-administration of nalbuphine, butorphanol and pentazocine by morphine post-addict rats. Rats were prepared with permanent EEG and EMG electrodes and indwelling IV cannulae, made tolerant to and physically dependent on morphine, then trained to lever press for morphine IV self-injections on a fixed ratio (FR) 20 schedule of reinforcement. Rats were then spontaneously withdrawn from morphine. When these morphine post-addict rats were returned to the experimental cages three to four weeks later, they were found to reestablish self-administration of morphine as well as to establish self-administration of nalbuphine, butorphanol and pentazocine. Suppression of REM sleep for at least 30 min was apparent following self-injections of these agents. After the stabilization of self-injection patterns, withdrawal from nalbuphine and pentazocine was found to be associated with intense abstinence symptoms. However, withdrawal from morphine and butorphanol was not. It can be concluded that while drug-seeking behavior for the above narcotics in morphine post-addict rats was analogous as measured by self-administration, nalbuphine and butorphanol appeared to produce lower levels of physical dependence.

Effects of levo-alpha-acetylmethadol (LAAM) on morphine self-administration in the rat

Rats bearing cerebrocortical electrodes for recording the electroencephalogram (EEG) were rendered tolerant to and physically dependent on morphine and subsequently trained to self-administer morphine (10 mg/kg injection) through a chronic intravenous cannula. Morphine was available for self-administration 24 h/day. Once morphine intake had stabilized (10-12 injections/day), levo-alpha-acetylmethadol (LAAM) was administered noncontingently via a chronic intragastric (IG) cannula as a single daily dose of either 1 or 4 mg/kg. These morphine self-administering rats were maintained on daily LAAM treatment for 12 consecutive days. Analysis of the patterns of lever pressing, morphine self-injections, and sleep-awake behavior revealed that daily IG administration of LAAM effectively suppressed morphine self-administration. The 1 mg/kg dose of LAAM reduced morphine intake by 30%-50%, while 4 mg/kg produced an 80%-90% decrease. The reduction in morphine self-administration occurred in the absence of overt signs of narcotic withdrawal, behavioral toxicity, or disruption of sleep-awake behavior in these rats. Termination of LAAM maintenance resulted in a gradual return of level pressing and morphine intake to pre-LAAM levels.

Narcotic abstinence in dependent rats: EEG and behavioral correlates

The purpose of the study was to assess and compare EEG and behavioral correlates of abstinence from morphine, methadone, LAAM, NLAAM, and DNLAAM in dependent rats. Rats were initially trained to lever press for self-injections on a FR-20 schedule of reinforcement. Following substitution of saline for each of the narcotic agonists. REM sleep was significantly suppressed during morphine, methadone, and NLAAM abstinence, but not during LAAM and DNLAAM abstinence. Significant increases in lever pressing for saline during abstinence from morphine, methadone, and NLAAM emerged earlier than with LAAM and DNLAAM. Significant increases in head-shake behavior occurred during morphine, methadone, NLAAM, and DNLAAM abstinence, but not during LAAM abstinence. These results demonstrated further pharmacodynamic differences between the five narcotics studied. Our findings suggested that in dependent rats abstinence from LAAM was the least severe when compared with abstinence from any of the other four narcotic studied.

Diurnal variations in REM and NREM sleep EEG power spectra in the rat

Diurnal variations were observed in the EEG power spectra of REM sleep and non-REM (NREM) sleep in the rat. Diurnal variations occurred in peak EEG frequency and spectral power (0-27 Hz and 5-9 Hz bands) during REM sleep. During NREM sleep diurnal variations were observed in spectral power in the 0-27 Hz and 0-4 Hz bands. The significance of these findings is discussed in terms of correlative data involving diurnal variations in neurotransmitters and hormones, all of which have been implicated in the induction or maintenance of sleep states.

Electroencephalographic and behavioral tolerance to and cross-tolerance between D-Ala2-methionine-enkephalinamide and morphine in the rat

Rats were given repeated intraventricular (i.vt.) injections of D-enkephalin (20 microgram/4 hr) or morphine (20 microgram/4 hr) for 72 to 96 hr during electroencephalograman(EEG) recording. Initial epileptiform EEG and associated wet-dog shakes occurred following D-enkephalin but not morphine. The epileptoid EEG progressed to a continous high-voltage EEG synchrony similar to morphine and was associated with behavioral stupor. Rapid eye movement sleep was also suppressed. Repeated administration of D-enkephalin or morphine produced tolerance to their effects. When challenged with i.vt. morphine, D-enkephalin-tolerant rats were cross-tolerant to morphine. Likewise, morphine-tolerant rats were cross-tolerant to D-enkephalin. While the morphine-tolerant rats demonstrated a marked abstinence syndrome when challenged with naloxone (10 mg/kg i.p.), no abstinence signs were observed in the D-enkephalin-tolerant rats. The demonstration of tolerance and cross-tolerance between morphine and D-enkephalin suggests a similar mechanism of action, but the differential development of physical dependence may entail different mechanisms or receptor sensitivities for this effect. These findings of similarities and differences in the acute and chronic effects of D-enkephalin and morphine support the contention that heterogenous opiate receptors may mediate their pharmacologic actions.

Spontaneous vs. naloxone-induced abstinence in dependent rats self-administering L-alpha-acetylmethadol (LAAM) or morphine

Rats maintained dependence by the self-administration of LAAM or morphine. Following the substitution of saline for LAAM, REM sleep was not disrupted, and the frequency of lever pressing for saline self-injections peaked at about 24 hr. In contrast, following the substitution of saline for morphine, REM sleep was suppressed for 24 hr while the frequency of lever pressing for saline self-injections peaked within 8 hr. When abstinence was induced by hourly iv naloxone injections, REM sleep occurrences were suppressed to a similar degree and for similar durations during naloxone-induced abstinence from both morphine and LAAM. These results suggest that the level of physical dependence maintained during self-administration of LAAM and morphine was similar. The relatively mild abstinence syndrome that was seen during saline substitution in LAAM-dependent rats was most likely related to the long plasma half-lives of the pharmacologically active N-demethylated metabolites of LAAM.

Morphine self-administration and EEG power spectra in the rat

Power spectral analyses were used to study changes in cortical EEG during morphine self-administration in freely-moving dependent rats prepared with chronic cortical and muscle electrodes and with permanent indwelling IV cannulae. As time progressed from a morphine self-injection toward another injection, a significant spectral shift of the EEG to lower frequencies occurred during successive REM sleep episodes. Each morphine self-injection reinstated the predominance of higher frequencies in the EEG spectra. These EEG changes which preceded lever pressing may reflect changes in morphine plasma levels and in the state of the CNS that precede drug-seeking behavior.