Intracellular Physiology of the Rat Suprachiasmatic Nucleus: Electrical properties, Neurotransmission & Effects of Neuromodulators
Abstract
Knowledge of the neuronal membrane properties and synaptic physiology of the suprachiasmatic nucleus (SCN) is critical for an understanding of the cellular basis of circadian rhythms in mammals. The hypothalamic slice preparation from rodents and a combination of electrophysiological techniques (i.e., extracellular single- and multiple-unit recording, intracellular recording, and whole-cell patch clamp) were used to study (1) the role of excitatory and inhibitory amino acids (i.e., glutamate and GABA) in synaptic transmission, (2) the membrane properties of SCN neurons, and (3) the mechanisms of neuronal synchronization. Antagonists for N-methyl-D-aspartate (NMDA) and non-NMDA receptors blocked excitatory postsynaptic potentials (EPSPs) evoked by stimulation of the optic nerve other sites when SCN cells were depolarized or at rest, respectively. Bicuculline blocked inhibitory postsynaptic potentials (IPSPs) that were evoked by local stimulation or that occurred spontaneously. The IPSP reversal potential was near the Cl(-) equilibrium potential, and was shifted to depolarized levels by raising intracellular (Cl(-)). Thus, glutamate and GABA appear to mediate fast excitatory inhibitory synaptic transmission in the SCN. Some SCN neurons, but not all of them, has low-threshold Ca(2+) spikes and time-dependent inward rectification, thus indicating that the electrical properties of SCN neurons are not homogenous. Neurons with a firing rate >6 Hz had a regular pattern, and neurons with a rate <4 Hz had an irregular pattern; since both the firing rate and pattern could be modified with injected currents, SCN neurons with different firing patterns are unlikely to represent distinct classes of cells.
Document Details
- Document Type
- Technical Report
- Publication Date
- Apr 30, 1993
- Accession Number
- ADA268829
Entities
People
- F. E. Dudek
Organizations
- Colorado State University