THE ORGANIZATION OF THE SUPRACHIASMATIC CIRCADIAN PACEMAKER OF THE RAT AND ITS REGULATION BY NEUROTRANSMITTERS AND MODULATORS

The long-term goal of our research is to understand how cells of the s uprachiasmatic nucleus (SCN) are organized to form a 24-hr biological clock, and what roles specific neurotransmitters and modulators play i n timekeeping and resetting processes. We have been addressing these q uestions by assessing the pattern of spontaneous neuronal activity, us ing extracellular and whole-cell patch recording techniques in long-li ved SCN brain slices from rats. We have observed that a robust pacemak er persists in the ventrolateral region of microdissected SCN, and hav e begun to define the electrophysiological properties of neurons in th is region. Furthermore, we are investigating changing sensitivities of the SCN to resetting by exogenous neurotransmitters, such as glutamat e, serotonin, and neuropeptide Y, across the circadian cycle. Our find ings emphasize the complexity of organization and control of mammalian circadian timing.