Intracellular Physiology of the Rat Suprachiasmatic Nucleus: ElectricalProperties, Neurotransmission, and Effects of Neuromodulators

摘要

Our primary aim has been to study the electrophysiology of suprachiasmaticnucleus (SCN) neurons, with a focus on the interplay between intrinsic electrophysiological properties, amino-acid-mediated synaptic transmission, and neuromodulation. We have continued to study the role of excitatory and inhibitory amino acids (i.e., glutamate and GABA) in fast synaptic transmission in the SCN. Our work has provided strong evidence that these transmitters mediate all, or nearly all, of the fast synaptic potentials in virtually all SCN neurons. Preliminary experiments, however, suggest that a circadian rhythm of electrical activity persists after post-synaptic pharmacological blockade of these transmitter systems. Intracellular and whole-cell patch-clamp studies are being undertaken on intrinsic membrane properties, which we have found to be heterogeneous across the SCN. Particularly interesting is our recent observation that synchronous bursts of action potentials can occur in the SCN after chemical synapses have been blocked with low-calcium solutions and amino-acid-transmitter antagonists. Finally, we have continued several lines of experimentation partially supported by this grant on the supraoptic and paraventricular nuclei and the preoptic area of the hypothalamus, thus allowing a direct comparison between the SCN and other major regulatory areas of the hypothalamus. Our experiments continue to be aimed at providing a rigorous understanding of how transmitters and neuromodulators interact with intrinsic membrane properties to regulate the electrical activity of neurons in the SCN and other areas of the hypothalamus.