Intracellular Physiology of the Rat Suprachiasmatic Nucleus: Electrical Properties, Neurotransmission, and Effects of Neuromodulators.
Final rept. 1 Nov 1989-30 Jun 1992,
CALIFORNIA UNIV LOS ANGELES MENTAL RETARDATION RESEARCH CENTER
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The aim of this research has been to gain an understanding of the neurophysiology of the suprachiasmatic nucleus SCN, with emphasis on intrinsic electrical properties, synaptic and non-synaptic transmission, and neuromodulation. We have studied the role of excitatory and inhibitory amino acids i.e., glutamate and GABA in fast synaptic transmission. Our work has provided strong evidence that these transmitters mediate most, if not all, of the synaptic potentials in SCN neurons. Experiments with extracellular recordings indicate that a circadian rhythm of electrical activity persists after pharmacological blockade of these transmitter systems. Intracellular recordings showed that the intrinsic membrane properties are not homogeneous across the SCN, that some neurons have low-threshold Ca2 spikes and inward rectification, and that the firing pattern depends on firing rate. We have recently found 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 to study the supraoptic and paraventricular nuclei and the preoptic area of the hypothalamus, thus allowing a direct comparison between the SCN and other areas of the hypothalamus. Our experiments should provide a rigorous understanding of how neurotransmitters, local neuronal circuits and intrinsic membrane properties regulate the electrical activity of neurons in the SCN and other hypothalamic areas. Hypothalamus, GABA, suprachiasmatic nucleus, excitatory amino acids, glutamate, electrophysiology.
- Anatomy and Physiology