Tracer and electrical coupling of rat suprachiasmatic nucleus neurons

• Published in: Neuroscience 1997-04, Vol.77 (4), p.1059-1066
• Main Authors: Jiang, Z.-G, Yang, Y.-Q, Allen, C.N
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Biotin - analogs & derivatives; Chronobiology; circadian rhythm; Circadian Rhythm - physiology; Coloring Agents; dye coupling; Electric Conductivity; electrical transmission; Fundamental and applied biological sciences. Psychology; neurobiotin; Neurons - physiology; Patch-Clamp Techniques; Periodicity; Rats; Rats, Sprague-Dawley; suprachiasmatic nucleus; Suprachiasmatic Nucleus - cytology; Suprachiasmatic Nucleus - physiology; Vertebrates: anatomy and physiology, studies on body, several organs or systems
• ISSN: 0306-4522; 1873-7544
• DOI: 10.1016/S0306-4522(96)00539-8

Whole-cell recording from single neurons of the suprachiasmatic nucleus with an electrode containing the tracer neurobiotin resulted in the staining of multiple neurons in 30% of the cases. Typically, one neuron was darkly stained with dendritic processes and an axon clearly visible while other neurons were lightly stained. The darkly-stained cells were identified as the recorded neuron and tracer-coupled to one to five lightly stained neurons. The resting membrane potential, input membrane conductance, membrane capacitance, the decay time constant and the maximum H-current amplitude of the recorded neurons with tracer-coupled cells were not significantly different from those of neurons not showing tracer coupling. Stimulation of the preoptic area activated an antidromic action potential or an all-or-none small slow inward current in some neurons when the synaptic transmission was blocked by a calcium-free/Mn 2+ solution. The small slow inward current did not “collide” with an orthodromically activated action spike suggesting that the current represents the signal from an electrotonically-coupled neuron. In addition, the frequency of biphasic field currents from a neighbouring cell firing were increased by depolarization and decreased by hyperpolarization of the recorded cell. These data demonstrate a chemical and electrical low-resistance coupling of suprachiasmatic nucleus neurons, which could be important in synthesizing the suprachiasmatic nucleus circadian rhythm.