Impact of Marine Drugs on Animal Reproductive Processes

The discovery and description of bioactive substances from natural sources has been a research topic for the last 50 years. In this respect, marine animals have been used to extract many new compounds exerting different actions. Reproduction is a complex process whose main steps are the production and maturation of gametes, their activation, the fertilisation and the beginning of development. In the literature it has been shown that many substances extracted from marine organisms may have profound influence on the reproductive behaviour, function and reproductive strategies and survival of species. However, despite the central importance of reproduction and thus the maintenance of species, there are still few studies on how reproductive mechanisms are impacted by marine bioactive drugs. At present, studies in either marine and terrestrial animals have been particularly important in identifying what specific fine reproductive mechanisms are affected by marine-derived substances. In this review we describe the main steps of the biology of reproduction and the impact of substances from marine environment and organisms on the reproductive processes

A slowly inactivating sodium current (INa2) in the plateau range in canine cardiac purkinje single cells.

The action potential of Purkinje fibres is markedly shortened by tetrodotoxin, suggesting the possibility that a slowly inactivating sodium current might flow during the plateau. The aim of the present experiments was to investigate, in canine cardiac Purkinje single cells by means of a whole cell patch clamp technique, whether a sodium current slowly inactivates at less negative potentials and (if so) some of its distinctive characteristics. The results showed that a 500 ms depolarizing step from a holding potential of −90 mV to −50 mV induced the fast inward current INa (labelled here INa1).With steps to−40 mV or less negative values, a slowly decaying component (tentatively labelled here INa2) appeared, which peaked at −30 to −20 mV and decayed slowly and incompletely during the 500 ms steps. The INa2 was present also during steps to −10 mV, but then the transient outward current (Ito) appeared.When the holding potential (Vh) was decreased to−60 to−50 mV, INa2 disappeared even if a small INa1 might still be present. Tetrodotoxin (30 μM), lignocaine (100 μM) and cadmium (0.2mM; but not manganese, 1mM) blocked INa2. During fast depolarizing ramps, the rapid inactivation of INa1 was followed by a negative slope region. During repolarizing ramps, a region of positive slope was present,whereas INa1 was absent. At less negative values of Vh, the amplitude of the negative and positive slopes became gradually smaller.Gradually faster ramps increased the magnitude of the negative slope, and tetrodotoxin (30 μM) reduced or abolished it. Thus, Purkinje cells have a slowly decaying inward current owing to Na+ entry (INa2) that is different in several ways from the fast INa1 and that appears important for the duration of the plateau