Effect of capsaicin on voltage-gated currents of trigeminal neurones in cell culture and slice preparations

Effects of capsaicin on voltage-gated currents were examinedin vitro by whole-cell patch-clamp recordings from small neurones of rat trigeminal ganglia either in slice preparations or in different cell cultures. Cells were classified as sensitive to capsaicin if they responded with inward current and/or conductance change to the agent in nanomolar concentration. Capsaicin (150 to 330 nM) in sensitive cells reduced the mixed inward current evoked by depolarizing step or ramp commands in all preparations. In cultured cells, the inward current was depressed to 32.78±26.42% (n = 27) of the control. Both the tetrodotoxin-sensitive and -resistant inward currents were affected. The data support the concept that capsaicin besides acting on VR-1 receptors inhibits also some voltage gated channels. In 34 cultured cells, capsaicin increased the slope conductance to 170.5±68%. Percentage of capsaicin sensitive cells observed in nerve growth factor-treated cultured cell populations was higher (77.8%) than in the two other preparations (14.3 or 38.8%). It is concluded that 1) depression of the voltage-gated currents may play an important role in the functional desensitization of the sensory receptors and in the analgesic effect induced by the agent and 2) cell body of sensory neurones under native condition seems less sensitive to capsaicin then that of cells cultured in the presence of nerve growth factor

A comparative methodical study of the faecal steroid analysis on birds: looking for a valid method of testosterone determination

In a comparative study, a relatively simple and high sensitivity method was developed for analysis of testosterone-equivalent(s) in the faeces of different bird species. To determine the recovery of extractions and purifications, tritium-labelled testosterone was added to the wet samples. Then the samples were treated with sodium dodecil sulphate (SDS), an emulsificator to “open-up” the complex, lipid-coated particles of faecal samples. This emulsification resulted in the decrease of the quantity of interfering substances after diethyl-ether extraction and the linearity of the measured testosterone equivalents from aliquots in the range of 2 and 10 mg of faeces. In the RIA, we applied a group specific polyclonal testosterone antibody which cross-reacted with reduced metabolites and at a certain level with sulphate conjugates as well. The use of Helix enzymes did not modified significantly the results of the analysis relating to a low level of conjugated androgens in the faecal extracts. The biological validity of the method was tested on domestic cockerels, where between the plasma and faecal testosterone values a four hours phase shift was observed, with a correlation of 0.6355. This method is suitable for “non invasive”, behavioural-ethological studies

Seasonal changes in plasma dehydro-epiandrosterone (DHEA) levels of domestic geese

Changes in plasma DHEA, testosterone (T) and 17-B-oestradiol (E2) levels were examined in domestic geese of both sexes in the fall and winter. The levels of steroid hormones were determined in blood plasma by means of radio-immunoassay (RIA). A so-called second (autumn) cycle was induced in geese via a dark-room preparation and natural keeping conditions. The plasma levels of DHEA showed a minor peak at onset of the autumn breeding and a major one prior to the more intense spring reproduction in both sexes. The seasonal curves of plasma DHEA appeared fairly similar in ganders and layers and without considerable differences between the absolute values. In ganders, plasma DHEA peaks preceded the elevations in T levels in the fall and spring alike. With layers, in turn, the autumn and spring peaks of plasma DHEA appeared after the peaks in E2 levels. With ganders, the concentration of plasma T seemed to predominate between the two androgens throughout the experimental period. With layers, in turn, the concentration of DHEA surpassed the level of plasma E2 at the time of the peak periods and other times during the study, as well. In domestic geese, DHEA is probably involved in the autumn physiological processes and the induction of reproduction during fall and early spring periods, alike

Attempts on artificial induction of sexual maturation of sterlet (Acipenser ruthenus) and identification of late spermatogenesis stage in hermaphroditic fish

Abstract Most of the 27 species of sturgeons are endangered or close to extinction which is connected to habitat degradation, water pollution and overfishing. Conservation programmes are facing the problem of late maturation which can be reached between 5 and 11 years depending on the species and gender. The aim of our study was to investigate the possibility of shortening the sexual maturation using hormonal administration, and measure the blood serum hormone content to distinguish different genders and maturation stages. There was no effect of a 20-week-long hormonal treatment (10 mg carp pituitary/bodyweight kg/week) on the sexual maturation. The number of females was relatively high (67.6% n = 23) and the number of males was relatively low (11.8%, n = 4). Moreover, the number of hermaphroditic fish was surprisingly high (20.6%, n = 7) and appeared independently from hormone administration. Hermaphroditic fish had fully developed spermatozoa and could be distinguished by the increased level of testosterone hormone in blood serum