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Effects of 5-hydroxytryptamine (serotonin; 5-HT) on the anterior aorta and ventricle muscle of the marine gastropod Aplysia are characterized. Bath-applied 5-HT depolarizes muscle fibers and causes tension increases in both the anterior aorta and ventricle above ca. 10(-9) M. Iontophoretically applied 5-HT caused localized depolarizations of anterior aorta muscle fibers. 5-HT increases the levels of adenosine-3',5'-cyclic monophosphate (cAMP) markedly in the anterior aorta of A. kurodai and A. californica and in the ventricle of A. kurodai. Effects of 5-HT on the contractility of and cAMP synthesis in the anterior aorta and ventricle are both blocked by methysergide. 5-HT and cAMP analogs stimulate 45Ca2+ efflux from the ventricle, implying that the effects of cAMP on contractility involve intracellular Ca2+ movements.

SUMMARY1. The effects of catechol on various ionic channels of isolated primary afferent neurones of the bull-frog were examined by a single-suction-electrode clamp system, which combined internal perfusion and current or voltage clamp using an electronic switching circuit.2. Catechol was found to inhibit rather specifically the fast K+ current as does 4-aminopyridine (4-AP). Ca2+, Na+ and slow K+ currents were not affected.3. Although both 4-AP and catechol were inhibitors of the fast K+ channels, their sites of action were quite different. Catechol was effective when applied on the external surface of the cell membrane whereas 4-AP acted preferably internally.4. We assumed that a single fast K+ channel has two distinct sites for blockers: the catechol site is exposed to the external medium or situated at the outer orifice of the pore, and the 4-AP site is located within the same channel but is more easily accessible from inside the nerve cell than outside.5. The 4-AP and catechol sites were not, however, completely separate and independent of each other since a synergistic interaction was observed between catechol and 4-AP.

We investigated the effects of estriol (E3) on endothelial function and bone mineral density (BMD) in very elderly women. Twenty-four very elderly women (80 +/- 3.5 years old) were administered CaCl2 with or without estriol treatment (2 mg/day) for 30 weeks (hormone replacement treatment [HRT] group vs control group). Endothelium-dependent flow-mediated dilatation (FMD), endothelium-independent dilatation by nitroglycerin of the brachial artery, and BMD were assessed. Levels of plasma lipids and apoproteins were not changed; however, both plasma E3 and E2 were substantially increased (E2, 4.6 to 31.3 +/- 8.1; E3, <5 to 45.3 +/- 7.9 pg/mL) by HRT. The FMD value was also increased by HRT, as were the plasma nitrite/nitrate and cGMP values. The response to nitroglycerin was not changed. The BMD was increased by HRT, but decreased in the control group. There were significant differences between the HRT group and control group after 30 weeks' treatment in the levels of osteocalcin, P1CP, and urinary deoxypiridinoridine. E3 significantly improved BMD by inhibiting bone resorption. Endothelial function was improved in line with the antiatherosclerotic effects. E3 might be effective for use in HRT in elderly patients.