Home | About the Smale Lab | Take a virtual tour | Contact information
Smale Lab Virtual Tour: Research Strategies and Techniques
(Page 1 of 4)
Virtual Tour: Research Strategies | Grass Rat Colony | Laboratory Space | Nuñez Lab
Research in the Smale Lab is conducted using a variety of techniques. Previous work in our laboratory has ranged from field and laboratory studies of behavior to molecular biology experiments aimed at examining the expression of specific genes or marker proteins in the rodent brain.
Field work
Live trapping in Kenya.
Trapping data (black bars = Arvicanthis)
Field studies have included both direct observation and live trapping (left) to study the circadian organization of foraging behavior in the grass rat. Grass rats restrict their foraging to daytime hours and are rarely trapped during the night (right).
Behavior
Our lab uses the VitalView automated data collection system to record behavioral and physiological data using running wheels and motion detectors or implanted transmitters. We have also used time-lapse video recording to monitor behavior. All rooms used for behavioral studies have timed lighting controls, and our care facility is kept light-tight with constant dim red lighting for safe entry during the dark phase.
A rack of animals housed with running wheels. We also use motion detectors and implanted transmitters to monitor behavior.
Each wheel is connected to an automatic recording system for behavioral analysis. Animals are housed individually when given access to wheels.
Behavioral analyses are conducted using direct observation of behavior using time-lapse video (left), or by examining the output of our data collection system (right).
Still image from time lapse video screen capture showing mating behavior in the grass rat.
Actograms depicting wheel running records from a day-active grass rat (top) and a night-active one (bottom). Each horizontal line depicts one 48 hour period.
Some behavioral work has focused on individual differences in activity patterns in our study animals. Although all grass rats are diurnal animals, approximately 30% of grass rats in our colony are capable of spontaneously switching to a night-active pattern of behavior when given continuous access to a running wheel (above right). The day- and night-active grass rats differ with respect to overall organization of locomotor activity (below left) and the organization of behavioral sleep throughout the day (below right).
Activity patterns in day-active (open circles) and night-active grass rats (closed circles) over a 24 hour period.
Behavioral sleep in day-active and night-active grass rats.
Immunohistochemistry
One method used to examine the neural substrates underlying behaviors in our lab is immunohistochemistry. Antibodies raised against specific proteins and peptides are used to label tissue with a chromagen, typically resulting in a brown or black stain where the target protein is present.
A coronal view of tissue from a grass rat brain that has been stained using immunohistochemical procedures to reveal cells and fibers containing the peptide vasopressin.
A high magnification photograph of cells that have been double labeled for the detection of a peptide called orexin, and a nuclear protein called c-Fos. The presence of c-Fos in a cell indicates a high level of activity, and it changes in predictable ways over the course of a day.
Tract-tracing
In addition to labeling tissue for peptides that are present, our lab uses stereotaxic techniques to inject chemical tracers that allow us to examine the connections between different populations of neurons in the brain. The stereotaxic apparatus (left) allows us to precisely target specific brain regions for injections of tracer (right).
A stereotaxic surgical apparatus used to inject tracers. This apparatus enables precise targeting of specific brain regions.
Tissue labeled for cholera toxin beta, a retrograde tract tracer. This injection is centered on the suprachiasmatic nucleus.
Typical chemical tracers used in our laboratory include biotinylated dextran amine (BDA) and cholera toxin beta (CTb). By combining immunohistochemical and stereotaxic techniques we can examine neural connections between cells expressing specific proteins. Current projects include the use of light or confocal microscopy to study contacts between tracer-labeled fibers and cells labeled using standard immunohistochemistry.
Fluorescent labeling for the tracer CTb (green) and the peptide orexin (red). The CTb injection was centered on the intergeniculate leaflet in the thalamus.
Fluorescent labeling for gonadotropin hormone-releasing hormone (GnRH) cells (red) and the tracer BDA (green). The BDA injection was centered on the lower subparaventricular zone of the hypothalamus.
Other Techniques
Other techniques used in our laboratory include in situ hybridization for examination of circadian gene expression patterns, cannulation to allow infusions of substances into the brain (left), and hormone treatments to examine the effects of hormonal state on reproductive behavior. Studies in collaboration with Dr. David Weaver (University of Massachusetts) seek to characterize circadian gene expression rhythms in the grass rat (right).
Ink injection used to mark the cannula placement site in a grass rat. This cannula was used to infuse peptides into the suprachiasmatic nucleus.
Circadian expression profiles of PK2, Per1, and Per2 mRNA in the grass rat suprachiasmatic nucleus. This study was performed in collaboration with Dr. David Weaver at the University of Massachussetts.
Research Strategies | Next: Grass Rat Colony »