In pyramidal neurons from the CA1 region of the rat hippocampus, Na+-dependent action potentials backpropagate over the dendrites in an activity-dependent manner. Consequently, later spikes in a train have smaller amplitudes when recorded in the apical arbors. We studied the effect of the cholinergic agonist carbachol (CCh) on this pattern of activity when spikes were evoked synaptically or ant...

The effects of tetrodotoxin (TTX) and saxitoxin (STX) on the action potentials recorded in Ca2+-free solution in the absence of Ca2+ and K+ currents were investigated in the Retzius cell of three hirudinid leech species (Hirudo medicinalis, Macrobdella decora and Poecilobdella granulosa) and in the glossiphoniid leech Haementeria ghilianii. In the four leech species, stimulation of the Retzius ...

Although substantial knowledge has been accumulated on cerebellar granule cell voltage-dependent currents, their role in regulating electroresponsiveness has remained speculative. In this paper, we have used patch-clamp recording techniques in acute slice preparations to investigate the ionic basis of electroresponsiveness of rat cerebellar granule cells at a mature developmental stage. The gra...

The influence of voltage-dependent conductances on the receptor potential of Limulus ventral photoreceptors was investigated. During prolonged, bright illumination, the receptor potential consists of an initial transient phase followed by a smaller plateau phase. Generally, a spike appears on the rising edge of the transient phase, and often a dip occurs between the transient and plateau. Block...

Increases in postsynaptic [Ca2+]i can result from Ca2+ entry through ligand-gated channels or voltage-gated Ca2+ channels, or through release from intracellular stores. Most attention has focused on entry through the N-methyl-D-aspartate (NMDA) receptor in causing [Ca2+]i increases since this pathway requires both presynaptic stimulation and postsynaptic depolarization, making it a central comp...

The effect of serotonin (5-HT) on somatic and dendritic properties was analyzed in pyramidal neurons from the CA1 region in slices from the rat hippocampus. Bath-applied 5-HT (10 microM) hyperpolarized the soma and apical dendrites and caused a conductance increase at both locations. In the dendrites (200-300 microm from the soma) trains of antidromically activated, backpropagating action poten...

Glial-neuronal communication was studied by monitoring the effect of intercellular glial Ca2+ waves on the electrical activity of neighboring neurons in the eyecup preparation of the rat. Calcium waves in astrocytes and Müller cells were initiated with a mechanical stimulus applied to the retinal surface. Changes in the light-evoked spike activity of neurons within the ganglion cell layer occur...

We have shown that calmidazolium (R24571) causes a transient increase in the cytosolic free Ca2+ concentration ([Ca2+]i) in Dictyostelium discoideum [Schlatterer and Schaloske (1996) Biochem. J. 313, 661-667]. Here we have used R24571 to artifically increase [Ca2+]i during light-scattering oscillations and have found that, depending on the time of addition during the oscillatory cycle, R24571 s...

The events that occur during chemotaxis of sperm are only partly known. As an essential step toward determining the underlying mechanism, we have recorded Ca2+ dynamics in swimming sperm of marine invertebrates. Stimulation of the sea urchin Arbacia punctulata by the chemoattractant or by intracellular cGMP evokes Ca2+ spikes in the flagellum. A Ca2+ spike elicits a turn in the trajectory follo...

The effect of the nonsteroidal antiestrogen tamoxifen on carbachol (CCh)-triggered intracellular Ca2+ surges was determined in granulosa cells from the two largest preovulatory follicles of laying hens. The intracellular calcium ion concentration ([Ca2+]i) was measured in cells loaded with the Ca(2+)-responsive fluorescent dye fura-2. Resting [Ca2+]i was 96 +/- 5 nM (n = 20), and CCh (1 mM) tri...