Loss of GABA co-transmission from cholinergic neurons impairs behaviors related to hippocampal, striatal, and medial prefrontal cortex functions

Introduction: Altered signaling or function of acetylcholine (ACh) has been reported in various neurological diseases, including Alzheimer's disease, Tourette syndrome, epilepsy among others. Many neurons that release ACh also co-transmit the neurotransmitter gamma-aminobutyrate (GABA) at synapses in the hippocampus, striatum, substantia nigra, and medial prefrontal cortex (mPFC). Although ACh transmission is crucial for higher brain functions such as learning and memory, the role of co-transmitted GABA from ACh neurons in brain function remains unknown. Thus, the overarching goal of this study was to investigate how a systemic loss of GABA co-transmission from ACh neurons affected the behavioral performance of mice. Methods: To do this, we used a conditional knock-out mouse of the vesicular GABA transporter (vGAT) crossed with the ChAT-Cre driver line to selectively ablate GABA co-transmission at ACh synapses. In a comprehensive series of standardized behavioral assays, we compared Cre-negative control mice with Cre-positive vGAT knock-out mice of both sexes. Results: Loss of GABA co-transmission from ACh neurons did not disrupt the animal's sociability, motor skills or sensation. However, in the absence of GABA co-transmission, we found significant alterations in social, spatial and fear memory as well as a reduced reliance on striatum-dependent response strategies in a T-maze. In addition, male conditional knockout (CKO) mice showed increased locomotion. Discussion: Taken together, the loss of GABA co-transmission leads to deficits in higher brain functions and behaviors. Therefore, we propose that ACh/GABA co-transmission modulates neural circuitry involved in the affected behaviors.

Assessing the importance of sex in a hippocampus-dependent behavioral test battery in C57BL/6NTac mice

Inclusion of male and female subjects in behavioral neuroscience research requires a concerted effort to characterize sex differences in standardized behavioral assays. Sex differences in hippocampus-dependent assays have been widely reported but are still poorly characterized. In the present study, we conducted a parametric analysis of spontaneous alternation, object recognition, and fear conditioning in a commonly used control strain, C57BL/6NTac. Our findings show largely similar performance between males and females across the majority of behavioral end points. However, we identified an important difference in nonassociative fear sensitization, whereby females showed an enhanced fear response to the 75-dB tone that is used as the conditional stimulus. In addition, we observed an impairment in object location performance in females that was ameliorated by more extensive habituation to handling. Together, these findings argue that sex differences in nonassociative fear responses to both novel auditory cues and novel objects need to be considered when designing and interpreting cognitive assays in C57BL/6 mice. Furthermore, this elevated fear sensitization could serve as a novel approach to model the increased incidence of anxiety disorders in women.

Measuring Behavior in the Home Cage: Study Design, Applications, Challenges, and Perspectives

The reproducibility crisis (or replication crisis) in biomedical research is a particularly existential and under-addressed issue in the field of behavioral neuroscience, where, in spite of efforts to standardize testing and assay protocols, several known and unknown sources of confounding environmental factors add to variance. Human interference is a major contributor to variability both within and across laboratories, as well as novelty-induced anxiety. Attempts to reduce human interference and to measure more "natural" behaviors in subjects has led to the development of automated home-cage monitoring systems. These systems enable prolonged and longitudinal recordings, and provide large continuous measures of spontaneous behavior that can be analyzed across multiple time scales. In this review, a diverse team of neuroscientists and product developers share their experiences using such an automated monitoring system that combines Noldus PhenoTyper® home-cages and the video-based tracking software, EthoVision® XT, to extract digital biomarkers of motor, emotional, social and cognitive behavior. After presenting our working definition of a "home-cage", we compare home-cage testing with more conventional out-of-cage tests (e.g., the open field) and outline the various advantages of the former, including opportunities for within-subject analyses and assessments of circadian and ultradian activity. Next, we address technical issues pertaining to the acquisition of behavioral data, such as the fine-tuning of the tracking software and the potential for integration with biotelemetry and optogenetics. Finally, we provide guidance on which behavioral measures to emphasize, how to filter, segment, and analyze behavior, and how to use analysis scripts. We summarize how the PhenoTyper has applications to study neuropharmacology as well as animal models of neurodegenerative and neuropsychiatric illness. Looking forward, we examine current challenges and the impact of new developments. Examples include the automated recognition of specific behaviors, unambiguous tracking of individuals in a social context, the development of more animal-centered measures of behavior and ways of dealing with large datasets. Together, we advocate that by embracing standardized home-cage monitoring platforms like the PhenoTyper, we are poised to directly assess issues pertaining to reproducibility, and more importantly, measure features of rodent behavior under more ethologically relevant scenarios.

Differential signalling induced by α7 nicotinic acetylcholine receptors in hippocampal dentate gyrus in vitro and in vivo

The activation of α7 nicotinic acetylcholine receptors (nAChRs) has been shown to improve hippocampus-dependent learning and memory. α7 nAChRs are densely expressed among several different cell types in the hippocampus, with high Ca²⁺  permeability, although it is unclear if α7 nAChRs mobilize differential signalling mechanisms among distinct neuronal populations. To address this question, we compared α7 nAChR agonist-induced responses (i.e. calcium and cAMP changes) between granule cells and GABAergic neurons in the hippocampal dentate gyrus both in vitro and in vivo. In cultured organotypic hippocampal slices, we observed robust intracellular calcium and cAMP increases in dentate granule cells upon activation of α7 nAChRs. In contrast, GABAergic interneurons displayed little change in either calcium or cAMP concentration after α7 nAChR activation, even though they displayed much larger α7 nAChR current responses than those of dentate granule cells. We found that this was due to smaller α7 nAChR-induced Ca²⁺ rises in GABAergic interneurons. Thus, the regulation of the Ca²⁺ transients in different cell types resulted in differential subsequent intracellular signalling cascades and likely the ultimate outcome of α7 nAChR activation. Furthermore, we monitored neuronal activities of dentate granule cells and GABAergic interneurons in vivo via optic fibre photometry. We observed enhancement of neuronal activities after nicotine administration in dentate granule cells, but not in GABAergic neurons, which was absent in α7 nAChR-deficient granule cells. In summary, we reveal a mechanism for α7 nAChR-mediated increase of neuronal activity via cell type-specific intracellular signalling pathways. KEY POINTS: α7 nicotinic acetylcholine receptors (nAChRs) are widely distributed throughout the central nervous system and regulate a variety of brain functions including learning and memory. Understanding the cellular signalling mechanisms of their activations among different neuronal populations is important for delineating their actions in cognitive function, and developing effective treatment strategies for cognitive deficits. We report that α7 nAChR activation leads to Ca²⁺ and cAMP increases in granule cells (but not in GABAergic interneurons) in hippocampal dentate gyrus in vitro, a key region for pattern separation during learning. We also found that nicotine enhanced granule cell (but not in GABAergic interneurons) activity in an α7 nAChR-dependent manner via in vivo fibre photometry recording. Based on our findings, we propose that differential responses to α7 nAChR activation between granule cells and GABAergic interneurons is responsible for the increase of excitation by α7 nAChR agonists in hippocampal circuits synergistically.

Prevalence of complementary and alternative medicine use in cancer patients

Interest in complementary and alternative medicine (CAM) has grown dramatically over the past several years. Cancer patients are always looking for new hope, and many have turned to nontraditional means. This study was conducted to determine the prevalence of complementary and alternative medicine use in cancer patients and what if any agents are being used. Approximately, 100 adult cancer patients in a private nonprofit South Florida hospital completed a descriptive cross-sectional survey questionnaire. The mean age of participants was 59 years; 42 patients were male and 58, female. According to survey results, 80% of patients reported using some type of CAM; 81% took vitamins, 54% took herbal products, 30% used relaxation techniques, 20% received massages, and 10% used home remedies. Among patients who took vitamins, 65% said they took a multivitamin, 39% took vitamin C, and 31%, vitamin E. The most common herbal remedies used were green tea, echinacea, shark cartilage, grape seed extract, and milk thistle. Meditation and deep breathing were the two most common relaxation techniques practiced. A large majority of cancer patients are using CAM. In light of the growing interest in CAM, health-care professionals need to be educated about the most common therapies used.

Docetaxel as an alternative to paclitaxel after acute hypersensitivity reactions

OBJECTIVE

To review the mechanism involved in paclitaxel-induced hypersensitivity reactions and to evaluate the potential use of docetaxel after acute hypersensitivity reactions (HSRs) to paclitaxel.

DATA SOURCES

Literature identified through a MEDLINE search (1966-September 2000) and through secondary sources.

DATA SYNTHESIS

HSRs to paclitaxel can be life-threatening. The exact etiology involved in paclitaxel-induced HSRs has not been fully elucidated; the reactions may be due to the Cremophor EL vehicle or to paclitaxel itself. Options for treatment following HSRs are limited. A rechallenge attempt can be made, but is not always successful. Docetaxel, a semisynthetic taxane, may have a role in therapy for patients unable to tolerate paclitaxel therapy. This review examines the etiology of paclitaxel-induced HSRs and the potential role of docetaxel following these acute reactions.

CONCLUSIONS

Docetaxel may be a viable alternative for patients who experience HSRs to paclitaxel.

Successful rechallenge with etoposide phosphate after an acute hypersensitivity reaction to etoposide

Hypersensitivity reactions to etoposide are reported infrequently and consist of hypotension, hypertension, flushing, diaphoresis, dyspnea, bronchospasm, and loss of consciousness. A 23-year-old woman experienced acute bronchospasm, tachycardia, hypoxia, and moderate hypertension minutes after an infusion of etoposide was begun. Symptoms resolved within an hour after administration of intravenous fluids, methylprednisolone, diphenhydramine, and oxygen. Subsequently, the patient was given etoposide phosphate without incident. To our knowledge, this is the first report of successful rechallenge with etoposide phosphate after an acute hypersensitivity reaction to etoposide.

Economic and clinical impact of a pharmacy-based filgrastim protocol in oncology patients

The effects of a clinical protocol for filgrastim use in oncology patients were studied. A chart review was conducted for every fourth oncology inpatient who received filgrastim at a community hospital between January and June 1996 to determine how filgrastim was being used in the hospital's oncology patients. The results were presented to the oncology committee, and a filgrastim protocol was implemented. The protocol stated that filgrastim would be discontinued when the absolute neutrophil count (ANC) was > or =1500 cells/mm3 for two days after the neutrophil nadir. Six months after the protocol was implemented, a follow-up evaluation was conducted by reviewing the chart for every fourth oncology patient who received filgrastim between November 1996 and April 1997. Twenty-one patient charts were reviewed before the protocol was implemented, and 34 charts were reviewed after implementation. The results showed there was compliance with the protocol for 19 (76%) of the 25 patients evaluable for compliance. Sixty-seven percent of patients were febrile before the protocol was implemented, and 56% were febrile afterward. Ten percent of patients had documented infections before implementation, compared with 12% afterward. The average ANC at which filgrastim was discontinued before and after the protocol was implemented was 6839 and 5538 cells/mm3, respectively. Filgrastim was discontinued by a pharmacist in 32% of cases. A $22,416 cost saving was achieved in the first six months after protocol implementation, with no compromise in clinical efficacy. A pharmacy-based protocol for discontinuing filgrastim therapy in oncology patients saved a community hospital more than $22,000 in the first six months withno adverse impact on the drug's effectiveness.