Justin L. LaPorte

Analyzing grooming microstructure in neurobehavioral experiments

Grooming is a commonplace, robust behavior in rodent species. It has been shown to be highly sensitive to a number of experimental factors, making it an ideal target for manipulation. The complex patterning of grooming in rodents, which usually proceeds in a cephalo-caudal direction and involves several distinct stages, can be dissected into its constituent parts and microstructures. Several grooming patterning analysis methods are described in the protocol that allow for an assessment of this behavior based on measurements of grooming activity and its sequencing. Additionally, grooming can be evaluated in reference to the regional distribution and syntax in which it occurs. Owing to the ever-increasing number of rodent models that have strong grooming phenotypes, this high-throughput in-depth analysis is becoming crucial for biomedical research.

Experimental Models of Anxiety for Drug Discovery and Brain Research

Animal models have been vital to recent advances in experimental neuroscience, including the modeling of common human brain disorders such as anxiety, depression, and schizophrenia. As mice express robust anxiety-like behaviors when exposed to stressors (e.g., novelty, bright light, or social confrontation), these phenotypes have clear utility in testing the effects of psychotropic drugs. Of specific interest is the extent to which mouse models can be used for the screening of new anxiolytic drugs and verification of their possible applications in humans. To address this problem, the present chapter will review different experimental models of mouse anxiety and discuss their utility for testing anxiolytic and anxiogenic drugs. Detailed protocols will be provided for these paradigms, and possible confounds will be addressed accordingly.

Altered 5-HT2C receptor agonist-induced responses and 5-HT2C receptor RNA editing in the amygdala of serotonin transporter knockout mice

BackgroundThe serotonin 5-HT2C receptor (5-HT2CR) is expressed in amygdala, a region involved in anxiety and fear responses and implicated in the pathogenesis of several psychiatric disorders such as acute anxiety and post traumatic stress disorder. In humans and in rodent models, there is evidence of both anxiogenic and anxiolytic actions of 5-HT2C ligands. In this study, we determined the responsiveness of 5-HT2CR in serotonin transporter (SERT) knockout (-/-) mice, a model characterized by increased anxiety-like and stress-responsive behaviors.ResultsIn the three-chamber social interaction test, the 5-HT2B/2C agonist mCPP decreased sociability and sniffing in SERT wildtype (+/+) mice, both indicative of the well-documented anxiogenic effect of mCPP. This 5-HT2C-mediated response was absent in SERT -/- mice. Likewise, in the open field test, the selective 5-HT2C agonist RO 60-0175 induced an anxiogenic response in SERT +/+ mice, but not in SERT -/- mice. Since 5-HT2CR pre-mRNA is adenosine-to-inosine (A-to-I) edited, we also evaluated the 5-HT2CR RNA editing profiles of SERT +/+ and SERT -/- mice in amygdala. Compared to SERT +/+ mice, SERT-/- mice showed a decrease in less edited, highly functional 5-HT2C isoforms, and an increase in more edited isoforms with reduced signaling efficiency.ConclusionsThese results indicate that the 5-HT2CR in the amygdala of SERT -/- mice has increased RNA editing, which could explain, at least in part, the decreased behavioral responses to 5-HT2C agonists in SERT -/- mice. These alterations in 5-HT2CR in amygdala may be relevant to humans with SERT polymorphisms that alter SERT expression, function, and emotional behaviors.

Analysis of Grooming Behavior and Its Utility in Studying Animal Stress, Anxiety, and Depression

In rodents, grooming is a complex and ethologically rich behavior, sensitive to stress and various genetic and pharmacological manipulations, all of which may alter its gross activity and patterning. Observational analysis of grooming activity and its microstructure may serve as a useful measure of stress and anxiety in both wild and laboratory animals. Few studies have looked at grooming behavior more than cursorily, though in-depth analysis of the behavior would immensely benefit fields utilizing rodent research. Here, we present a qualitative approach to grooming activity and patterning analysis in mice, which provides insight into the effects of stress, anxiety, and depression on this behavioral domain. The method involves quantification of the transitions between different stages of grooming, the percentages of incorrect or incomplete grooming bouts, as well as the regional distribution of grooming activity. Using grooming patterning as a behavioral endpoint, this approach permits assessment of stress levels of individual animals, allows identification of grooming phenotypes in various mouse strains, and has vast implications in biological psychiatry, including psychopharmacology, genetics, neurophysiology, and experimental modeling of affective disorders.

Perspectives on genetic animal models of serotonin toxicity

Serotonin syndrome, or serotonin toxicity, is a serious disorder attributable to exaggerated serotonergic function in the brain, most commonly after antidepressant overdose or after combining several psychotropic medications. Similar condition (serotonin syndrome-like behavior) can be evoked in animals experimentally, following administration of serotonergic drugs. In addition to pharmacological stimulation, some genetic and other factors may contribute to serotonin toxicity, prompting the need for new experimental genetic models relevant to this disorder. Here we discuss current problems and perspectives regarding genetic animal models of serotonin-related syndromes, and outline the potential utility of these models in experimental neurochemistry and clinical research.

The regular and light–dark Suok tests of anxiety and sensorimotor integration: utility for behavioral characterization in laboratory rodents

Animal behavioral models are crucial for neurobiological research, allowing for the thorough investigation of brain pathogenesis to be performed. In both animals and humans, anxiety has long been linked to vestibular disorders. However, although there are many tests of anxiety and vestibular deficits, there are few protocols that address the interplay between these two domains. The Suok test and its light–dark modification presented here appear to be suitable for testing this pathogenetic link in laboratory rodents. This protocol adds a new dimension to previously used tests by assessing animal anxiety and balancing simultaneously, resulting in efficient, high-throughput screens for testing psychotropic drugs, phenotyping genetically modified animals, and modeling clusters of human disorders related to stress/anxiety and balancing.

Refining psychiatric genetics: from ‘mouse psychiatry’ to understanding complex human disorders

Investigating the pathogenesis of psychiatric disorders is a complicated and rigorous task for psychiatric geneticists, as the disorders often involve combinations of genetic, behavioral, personality, and environmental factors. To nurture further progress in this field, a new set of conceptual tools is needed in addition to the currently accepted approaches. Concepts that consider cross-species trait genetics and the interplay between the domains of disorders, as well as the full spectrum of potential symptoms and their place along the pathogenetic continuum, are particularly important to address these needs. Here, we outline recent concepts and approaches that can help refine the field and enable more precise dissection of the genetic mechanisms contributing to psychiatric disorders.

Mouse Models for Studying Depression-Like States and Antidepressant Drugs

Depression is a common psychiatric disorder, with diverse symptoms and high comorbidity with other brain dysfunctions. Due to this complexity, little is known about the neural and genetic mechanisms involved in depression pathogenesis. In a large proportion of patients, current antidepressant treatments are often ineffective and/or have undesirable side effects, fueling the search for more effective drugs. Animal models mimicking various symptoms of depression are indispensable in studying the biological mechanisms of this disease. Here, we summarize several popular methods for assessing depression-like symptoms in mice and their utility in screening antidepressant drugs.

Experimental Models in Serotonin Transporter Research

The serotonin transporter is a key brain protein that modulates the reuptake of the neurotransmitter serotonin from synaptic spaces back into the presynaptic neuron. In this book, an international team of top experts introduce and explicate the role of serotonin and the serotonin transporter in both human and animal brains. They demonstrate the relevance of the transporter and the serotonergic system to substrates of neuropsychiatric disorders, and explain how this knowledge is translated into valid animal models that will help foster new discoveries in human neurobiology. Writing for graduate students and academic researchers, they provide a comprehensive coverage of a wide spectrum of data from animal experimentation to clinical psychiatry, creating the only book exclusively dedicated to this exciting new avenue of brain research.

The serotonin transporter knock-out rat: a review

This chapter dicusses the most recent data on the serotonin transporter knock-out rat, a unique rat model that has been generated by target-selected N-ethyl-N-nitrosourea (ENU) driven mutagenesis. The knock-out rat is the result of a premature stopcodon in the serotonin transporter gene, and the absence of the serotonin transporter has been confirmed at mRNA, protein, and functional levels. The serotonin transporter (SERT) plays a crucial role in serotonin reuptake and its absence has a huge effect on serotonin neurotransmission – exemplified by increased extracellular serotonin levels, reduced serotonin tissue/platelet/blood levels, and reduced evoked serotonin release – yet the animals appear normal and do not differ from wildtype littermates in respect to breeding and health. Behavioral phenotypes are only apparent when the animals are exposed to certain stimuli. For instance, the serotonin transporter knock-out rat displays increased stress sensitivity in a variety of anxiety- and depression-like tests, such as the elevated plus maze test and the forced swim test. Also remarkable, while general activity is not changed, the knock-out rats show a “neurotic-like” exploratory pattern. In line with the serotonin hypothesis of impulsivity, which argues that there is an inverse relationship between the two, serotonin transporter knock-out rats show reduced motor impulsivity in the five-choice serial reaction time task, and a reduction in social interaction during play and aggressive encounters. Interestingly, abdominal fat seems to be increased in the knock-out rat, despite normal body weight. Pharmacological compounds also elicit genotype-dependent responses in the knock-out rats.