Distinguishing between haloperidol's and decamethonium's disruptive effects on operant behavior in rats: use of measurements that complement response rate

HNF4A-AS1-encoded small peptide promotes self-renewal and aggressiveness of neuroblastoma stem cells via eEF1A1-repressed SMAD4 transactivation

Cancer stem cells play crucial roles in tumorigenesis and aggressiveness, while regulatory mechanisms in neuroblastoma (NB), a pediatric extracranial malignancy with highest incidence, are still unknown. Herein, a small 51-amino acid peptide (sPEP1) encoded by hepatocyte nuclear factor 4 alpha antisense RNA 1 (HNF4A-AS1) was identified in tumor tissues and cells, which facilitated self-renewal and aggressiveness of NB stem cells. MiRNA-409-5p interacted with HNF4A-AS1 to facilitate sPEP1 translation via recruiting eukaryotic translation initiation factor 3 subunit G, while sPEP1 repressed serum deprivation-induced senescence and promoted sphere formation, growth, or metastasis of NB stem cells. Mechanistically, sPEP1 directly interacted with eukaryotic translation elongation factor 1 alpha 1 (eEF1A1) to facilitate its binding to SMAD family member 4 (SMAD4), resulting in repression of SMAD4 transactivation and transcriptional upregulation of stem cell genes associated with tumor progression. Rescue experiments revealed that sPEP1 exerted oncogenic roles via facilitating physical interaction between eEF1A1 and SMAD4. Notably, knockdown of sPEP1 significantly repressed the self-renewal and metastasis of NB stem cells in vivo. High sPEP1 or eEF1A1 levels in clinical NB tissues were linked to poor patients' survival. These findings suggest that HNF4A-AS1-encoded sPEP1 promotes self-renewal and aggressive features of NB stem cells by eEF1A1-repressed SMAD4 transactivation.

CB1 antagonism produces behaviors more consistent with satiety than reduced reward value in food-maintained responding in rats

Cannabinoid CB1 antagonists are widely known to reduce motivation for food, but it is not known whether they induce satiety or reduce reward value of food. It may therefore be necessary to compare effects of altered satiety and reward food value in the same appetitive task, and determine whether CB1 antagonism produces a behavior pattern similar to either, both, or neither. A fine-grained analysis of fixed-ratio 10 (FR10) responding for palatable food initially included number and duration of, and between, all lever presses and food tray entries in order to differentiate the pattern of suppression of prefeeding from that caused by reducing the reward value of the pellets with quinine. Discriminant function analysis then determined that these manipulations were best differentiated by effects on tray entries, pellet retrieval latencies, and time of the first response. At 0.5 mg/kg, AM 6527 produced similar effects to reducing reward value, but at 1.0 and 4.0 mg/kg, effects were more similar to those when animals were satiated. We conclude that AM 6527 both reduced reward value and enhanced satiety, but as dose increased, effects on satiety became much more prominent. These findings contribute to knowledge about the behavioral processes affected by CB1 antagonism.

A review of the discovery, pharmacological characterization, and behavioral effects of the dopamine D2-like receptor antagonist eticlopride

Eticlopride is a substituted benzamide analog with high affinity and selectivity for dopamine (DA) D2-like receptors that was initially developed as a potential antipsychotic agent. A great deal of research has utilized this drug to better understand central DA receptor function, the role of D2-like receptors in behavior, and the influence of blockade of these receptors on several preclinical animal models. This review highlights research utilizing this drug and compares it to typical and atypical antipsychotics used clinically. First, we describe structure-activity relationships as it relates to binding at DA receptors and the consequences on behavior. This is followed by a discussion of several imaging strategies including the use of eticlopride for in vivo, in vitro, and ex vivo examination of DA D2-like receptor densities and function. Finally, we discuss the use of eticlopride in several behavioral models predictive of antipsychotic activity, extrapyramidal side effects (EPS), and learning and memory. While eticlopride is not used clinically, it remains a viable research tool for understanding DA receptor function and behavior.

Unlike haloperidol, clozapine slows and dampens rats' forelimb force oscillations and decreases force output in a press-while-licking behavioral task

In order to detect putative differences in the behavioral effects of clozapine and haloperidol, rats were trained to use a single forelimb to exert continuous pressure on a force-sensing operandum. Behavior was maintained by presenting a water-filled dipper for consumption only as long as the force remained above a specified level (the water fountain task). Effects of clozapine (2.0, 4.0, 8.0 mg/kg) and haloperidol (0.02, 0.04, 0.08, 0.12 mg/kg) on the forelimb force oscillations manifested during the operandum pressing episodes were analyzed with power spectral analysis and other quantitative methods. All rats exhibited force oscillations with a fundamental frequency near 7 Hz. Clozapine shifted the frequency to lower values (i.e., oscillation slowing), while haloperidol shifted oscilations to slightly higher frequencies. Moreover, clozapine reduced power in the region of the spectrum above 5 Hz. In contrast, haloperidol tended to increase power in these regions. Time domain analyses of the force-time waveforms indicated that haloperidol increased force emission during the hold phase of the forelimb response, and clozapine decreased this measure. The results are congruent with the high extrapyramidal side effects of haloperidol and the lack of such effects of clozapine in the clinic. In addition, clozapine may have antitremor effects in rats as it does in humans.

Microcatalepsy and disruption of forelimb usage during operant behavior: differences between dopamine D1 (SCH-23390) and D2 (raclopride) antagonists

In an experiment designed to distinguish between the behavioral consequences of treatment with SCH-23390, a D1 dopamine receptor blocker, and raclopride, a D2 antagonist, rats were trained to perform a water-reinforced forelimb operant response. Response rate and the duration of each forelimb contact with the operandum were recorded. In addition, the durations of the rat's visits to the reward well were detected by a photobeam which was blocked by the rat's muzzle as it remained at the reward well. In a between-groups dosing design, separate groups of rats (11-13 rats/group) received SCH-23390 (0, 0.01, 0.02, 0.04, 0.08, 0.12 mg/kg, IP, 30 min) or raclopride (0. 0.05, 0.1, 0.2, 0.4, 0.8 mg/kg, IP, 30 min) for 21 consecutive days. Quantitative analyses indicated that for comparable amounts of operant rate reduction, raclopride had a significantly greater tendency than SCH-23390 to increase the duration of operant responses and to increase the maximum muzzle entry duration (i.e., to induce microcatalepsy). The results support the idea that at relatively low doses D2 antagonism is more likely than D1 antagonism to produce effects identified preclinically with extrapyramidal side effects.