Depolarization of presynaptic terminals that arises from activation of presynaptic ionotropic receptors, or somatic depolarization, can enhance neurotransmitter release; however, the molecular mechanisms mediating this plasticity are not known. Here we investigate the mechanism of this enhancement at the calyx of Held synapse, in which presynaptic glycine receptors depolarize presynaptic termin...

Fluorometric calcium measurements have revealed presynaptic residual calcium (Ca(res)) to be an important regulator of synaptic strength. However, in the mammalian brain, it has not been possible to monitor Ca(res) in fibers that project from one brain region to another. Here, we label neuronal projections by injecting dextran-conjugated calcium indicators into brain nuclei in vivo. Currently a...

A-type potassium current generated by the K(V)4 family of channels is an important factor regulating the frequency, latency and dendritic backpropagation of spike discharge. The K(V)4.2 complex of K(V)4.2-KChIP3-DPP10c was recently shown to form a novel signaling complex through its association with T-type Ca(V)3.2 or Ca(V)3.3 calcium channel isoforms. Ca(V)3-mediated calcium entry was shown to...

The intracellular distribution of calcium has been studied in the mucosa of the avian shell gland, a tissue which transports large quantities of calcium during discrete time intervals. Ca(45) was administered to hens either in a single dose followed by sacrifice 5 min later or in repeated doses over an extended period followed by sacrifice 2 hr or 24 hr after the last injection. Subcellular fra...

We have studied the developmental changes of glutamate-induced calcium (Ca²⁺) response in primary cultured hippocampal neurons at three different stages of cultures, 3, 7-8, and 14-16 days in vitro (DIV), using fura-2 single-cell digital micro-fluorimetry. We found that glutamate-induced Ca²⁺ signaling was altered during development, and that two different ionotropic glutamate receptors, α-amin...

Fifteen actively growing lambs were divided into 3 groups and fed diets similar in all respects except for their calcium (Ca) and phosphorus (P) levels. The diets (Group 1; 1,47% Ca, 0,36% P: Group 2; 0,85% Ca, 0,47% P: Group 3; 0,37% Ca, 0,64% P) were fed to the animals for 98 days, when rib biopsy specimens were removed and analysed for Ca and P (Group 1; 21,20% Ca, 10,49% P: Group 2; 19,54% ...

Because the activity of the sodium pump (Na-K-ATPase) influences the secretion of aldosterone, we determined how extracellular potassium (K(o)) and calcium affect sodium pump activity in rat adrenal glomerulosa cells. Sodium pump activity was measured as ouabain-sensitive (86)Rb uptake in freshly dispersed cells containing 20 mM sodium as measured with sodium-binding benzofluran isophthalate. I...

An experimental model that allowed differentiation between endogenously and exogenously derived urinary oxalate was used to assess the effect of different forms and doses of ingested calcium on oxalate absorption and excretion. In replication 1 (R-1), subjects participated in three oxalate load (OL) tests: baseline (OL alone), calcium carbonate (OL with concomitant calcium carbonate ingestion),...

Secretion of the neuropeptide arginine vasopressin (AVP) from the neurohypophysis is optimized by short phasic bursts of action potentials with a mean intraburst frequency around 10 Hz. Several hypotheses, most prominently action-potential broadening and buildup of residual calcium, have been proposed to explain this frequency dependence of AVP release. However, how either of these mechanisms w...