Sleep & Circadian Physiology

Overview

Research interests in the Zhdanova laboratory center around the role of endogenous factors secreted into the cerebrospinal fluid in regulating behavior and physiological functions. We are specifically interested in two secretory organs, the pineal gland and the subcommissural organ (SCO), both of which secrete into the third brain ventricle, as well as into the blood stream.

sleepThe pineal gland is a well-characterized secretory gland, the most well known product of which is melatonin. Melatonin is secreted in a precise circadian fashion and its circulating levels are high at night and low during the day in the majority of species studied. Our data show that in diurnal species, including humans, melatonin is involved in daily sleep regulation, promoting sleep and adjusting its circadian timing. We are now addressing the mechanisms of melatonin effects on sleep and cognitive performance by using two animal models, diurnal primates (rhesus monkeys) and diurnal fish (zebrafish). Such combination of phylogenetically distant animal models allows us to broaden the methodological approaches, ranging from continuous recordings of primate sleep and cognitive performance to gene analysis in a genetically well-characterized zebrafish.

Little is known about the physiological role of another circumventricular gland we are studying, the SCO. This is an interesting brain structure, which secretes large glycoproteins into the lumen of the third ventricle. Some of these secretory proteins can aggregate and, in many species, form a mysterious Reissner’s fiber, spanning through the entire central canal of the spinal cord. We are focusing on the role the SCO might play in development, circadian rhythmicity and behavior.

Age-related decline in pineal and SCO activity or alterations induced by drugs of abuse may contribute to insomnia, cognitive alterations, reduced thresholds for anxiety or depression. We are addressing these issues by comparing secretory functions, sleep and behavior in old and young zebrafish and primates and in ‘drug abusing’ zebrafish.

Several collaborative projects add to the methodological approaches and the range of questions addressed by the laboratory:

  1. Role of the circadian rhythms and melatonin in human age-related insomnia with Drs. Friedman and Yesavage; Stanford University.
  2. Age-related changes in zebrafish behavior and circadian rhythms with Dr. Kishi; Dana Farber Cancer Institute, Harvard University.
  3. Neuronal activity in behaving zebrafish with Dr. O’Malley; Northeastern University.
  4. Pharmacokinetic analysis of melatonin in rhesus monkey CSF with Dr. Balis and McCully; NIH/NCI.

Signaling pathways involved in melatonin effects on sleep and cognition with Dr. Slack, Boston University School of Medicine, Department of Pathology.

Methodology

Primates

Telemetric polysomnographic (EEG, EOG, EMG) recordings of sleep patterns and core body temperature are conducted inspecially designed primate sleep lab, which includes six sound and light insulated ‘sleep chambers’.

Continuous recordings of locomotor activity, food intake and cognitive performance in monkeys that receive their food by operating individual touch screen computer monitors build into their home cages.

Zebrafish

High throughput locomotor activity assay, using image analysis system allows us to study the sleep-like state andcircadian rhythms in this diurnal vertebrate. Each of our four systems allows to record up to 160 larval or 30 adult fish at a time.

High speed video camera recordings (1000 frames per second) document detailed locomotor patterns in larval and adult zebrafish.

Confocal calcium imaging of neuronal activity in behaving zebrafish helps in our search of the specific neuronal structures involved in the behaviors of interest (collaboration with Dr. O’Malley; Northeastern University)

Construction of reporter genes using the Green Fluosrescent Protein (GFP) helps to record their temporal/spatial expression and regulation in the zebrafish

In vivo inhibition of protein expression by anti-sense RNAs allows to manipulate genes of interest and to study their contribution to development and behavior.

General Methods

Immunoassays for melatonin, cortisol, cAMP and cGMP in human and animal body fluids and tissues.

Analysis of protein expression by Western analysis.

People

Irina V. Zhdanova, MD, PhD
Dr. Zhdanova is the director of the laboratory. Her clinical and experimental research has contributed to a better understanding of the role the pineal hormone melatonin plays in normal sleep regulation in diurnal species and its clinical use in treating insomnia of different origin. Her studies have also showed that melatonin might modulate the effects of drugs of abuse, on both behavioral and molecular level. She is now focusing on the role the endogenous factors secreted into the third brain ventricle might play in regulating sleep, circadian rhytms, cognitive functions and emotional states.

Emmanuel Guélin, PhD
Emmanuel is a molecular biologist studying the physiological roles of melatonin receptors and f-spondin in zebrafish.

Ken Masuda, PhD
Ken is studying the role of melatonin and circadian rhytms in sleep and cognitive performance in young and aged rhesus monkeys.

Christina Quasarano, BS, Research Assistant
Christina received her Bachelor of Science in Marine Biology from the University of Massachusetts at Dartmouth. She is studying sleep and behavior in rhesus monkeys and zebrafish and is running the radio- and enzyme immunoassays for melatonin, cortisol and cyclic nucleotides. Christina is also managing the everyday life in the lab, ordering lab supplies, keeping an eye on our chemical hygiene and helping the new lab members adapting to the new environment.