Cellular bases of hippocampal EEG in the behaving rat.

Spreading depression (SD) and the related hypoxic SD-like depolarization (HSD) are characterized by rapid and nearly complete depolarization of a sizable population of brain cells with massive redi...

https://www.physiology.org/doi/pdf/10.1152/physrev.2001.81.3.1065

Mechanisms of Spreading Depression and Hypoxic Spreading Depression-Like Depolarization

The physiology and pharmacology of hippocampal formation theta rhythms

A versatile means of intracellular labeling: injection of biocytin and its detection with avidin conjugates

The thalamus as a neuronal oscillator.

Intracellular recordings from pairs of neurons in slices of rat hippocampus directly demonstrated electronic coupling between CA3 pyramidal cells. When two neurons were impaled simultaneously (as verified by subsequent double staining with horseradish peroxidase), current pulses injected into one cell caused voltage changes in other cells. These interactions were bidirectional. Fast prepotentials, historically thought to represent spike activity in dendrites, resulted from action potentials in other electronically coupled pyramidal cells. These data directly demonstrate electrotonic coupling between neurons in the mammalian brain and indicate that some fast prepotentials are coupling potentials. Coupling between pyramidal cells could mediate synchronization of normal rhythmic activity and of burst discharges during seizures.

https://science.sciencemag.org/content/sci/213/4509/782.full.pdf

Electrotonic coupling between pyramidal cells: a direct demonstration in rat hippocampal slices

Intracellular recordings from mammalian neuroendocrine cells showed that steady, injected currents can modify and block periodic spike bursts previously associated with increased neurohormone release. Spike afterpotentials could sum to form plateau potentials, which generated bursts and did not depend on axonal conduction or chemical synapses. Therefore, bursting involves a spike-dependent, positive-feedback mechanism endogenous to single neuroendocrine cells.

Burst discharge in mammalian neuroendocrine cells involves an intrinsic regenerative mechanism

Most magnocellular neurosecretory cells that terminate in the posterior pituitary secrete either vasopressin, oxytocin, or enkephalin. Intracellular injection of the fluorescent dye Lucifer Yellow into single magnocellular neurons in slices of rat hypothalamus resulted in dye transfer between these cells. Freeze-fracture replicas of these cells occasionally revealed gap junctions, which presumably contain channels that mediate the dye coupling. These two independent techniques strongly suggest that some mammalian neuropeptidergic cells are electrotonically coupled, providing a possible means for recruitment and synchronization of their electrical activity.

https://science.sciencemag.org/content/sci/211/4487/1187.full.pdf

Dye transfer through gap junctions between neuroendocrine cells of rat hypothalamus

Cholinergic excitation of supraoptic neurons in hypothalamic slices of rat.

The magnocellular neuropeptidergic cells (MNCs) of the paraventricular and supraoptic nuclei have been a model for biochemical and physiological studies of peptidergic neurons in the mammalian brain, but nearly all the electrophysiological studies of these vasopressinergic and oxytocinergic neuroendocrine cells are based on extracellular recordings. This paper reviews recent literature on electrophysiological properties of neurons in the magnocellular nuclei in which the rat in vitro slice preparation and intracellular recording were used. Spontaneously occurring action potentials and synaptic potentials (excitatory and inhibitory) have been observed in hypothalamic slices. The spike patterns have included slow and irregular firing, short rapid bursts of inactivating spikes, and slow phasic discharge with prolonged active and silent periods. Some studies have shown that increased osmolality causes neuronal firing, but this area is controversial. Intracellular injections of lucifer yellow have shown that some MNCs are dye-coupled and electron microscopic observations with the freeze-fracture technique have revealed occasional gap junctions, thus suggesting that some MNCs are electrotonically coupled. Both excitatory and inhibitory postsynaptic potentials have been evoked with extracellular stimulation. Therefore, action potentials, synaptic potentials, burst discharges, and probably electrotonic coupling have been found with intracellular recording in mammalian neuroendocrine cells. Future studies with intracellular recording and staining followed by immunohistochemical identification of cells should provide significant new information on the membrane physiology and synaptic pharmacology of vasopressinergic and oxytocinergic cells.

FE Dudek

Papers

Electrotonic coupling between pyramidal cells: a direct demonstration in rat hippocampal slices

Burst discharge in mammalian neuroendocrine cells involves an intrinsic regenerative mechanism

Dye transfer through gap junctions between neuroendocrine cells of rat hypothalamus

Cholinergic excitation of supraoptic neurons in hypothalamic slices of rat.

Intracellular electrophysiology of mammalian peptidergic neurons in rat hypothalamic slices.