0000000000525826
AUTHOR
J. Schäfer
Differential effects of potassium channel blockers on neurohypophysial release of oxytocin and vasopressin. Evidence for frequency-dependent interaction with the endogenous opioid inhibition of oxytocin release.
Isolated rat neurohypophyses were fixed by their stalks to a platinum wire electrode and superfused with Krebs-HEPES solution. Vasopressin and oxytocin released into the medium were determined by specific radioimmunoassays. Hormone secretion was increased by electrical stimulation of the pituitary stalk at different frequencies. The effects of several potassium channel blockers, tetraethylammonium (TEA) ions, 4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP) were tested. The release of vasopressin and oxytocin evoked by electrical stimulation with 900 pulses at 15 Hz (about 900 and 1,000 μU, respectively) was about 10 times higher than that evoked by 900 pulses at 3 Hz. Both 10 and 3…
Electronic structure of the spin-12quantum magnet TiOCl
We have studied the electronic structure of the spin-$1∕2$ quantum magnet TiOCl by polarization-dependent momentum-resolved photoelectron spectroscopy. From that, we confirm the quasi-one-dimensional nature of the electronic structure along the crystallographic $b$ axis and find no evidence for sizable phonon-induced orbital fluctuations as the origin for the noncanonical phenomenology of the spin-Peierls transition in this compound. A comparison of the experimental data to our own $\mathrm{LDA}+\mathrm{U}$ and Hubbard model calculations reveals a striking lack of understanding regarding the quasi-one-dimensional electron dispersions in the normal state of this compound.