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Characterization of serotonergic receptors in frog, rat and human adrenocortical cells
Sl9 s12-5
Symposium 13: Integrated control of brain-pituitary-peripheral axis. PolzoneM’ (Italy)
Chair: H. Habibi (Canada) and A.
Sugar-gated transduction ion channels localized in sensory processes of the insect taste cells Muraka and Kijima H Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
We examined the activities of sugar-gated transduction ion channels on the sensory processes of taste receptor cells of the fleshfly, Boettcherisca prregr:rina, by the patch-clamp technique. Sensory processes of taste cells grew out from the cut end of the taste hair on a labellum isolated from a pupa in the fly Ringer solution. They were swollen into small spheres after Ca” was removed from the incubation solution. We could patch clamp these spheres and recorded sugar-induced responses in the whole-cell and outside-out configurations. In the whole-cell voltage-clamp condition, sugar-induced inward currents were observed in about l/3 of the sensory processes. The current amplitudes and their fluctuations were increased in a dose-dependent manner. The conductance showed about 0 mV
of the reversal potential, and was depressed by the external Ca”. Outside-out patches also contirmcd thcsc properties. WC could record single channel currents responding sucrose in some outside-out patches. The single channel conductance was about 40 pS, and their mean open time was less than 1 ms. These results indicate that the existence of a novel receptorchannel complex type transduction channel on the sensory process membrane of the sugar receptor cell, which is activated directly by sucrose without mediation by second messengers.
s13-1 Characterization of serotonergic and human adrenocortical cells.
receptors in frog, rat
Contesse V, Lenglet S, Lefebvre H, Kuhn JM, Delarue C and Vaudry H Eur. Inst. Pept. Res. (IFRMP 23), Lab. Cell. Mol. Neuroendocr., INSERM U413, UA CNRS, Univ. Rouen, 76821 Mt-St-Aignan, France. Serotonin (5-HT) is produced by different types of cells within the adrenal gland of various vertebrate species. In vitro studies have shown that 5-HT is a potent stimulator of corticosteroid secretion in frog, rat and human. The aim of the present study was to investigate the type of receptors mediating the corticotropic effect of S-HT in these three representative species. In both frog and human, .5-HT4 receptor agonists mimic the stimulatory effect of 5-HT while 5-HT4 receptor antagonists totally block the effect of 5-HT on corticosteroid secretion. In contrast, in the rat adrenal gland, the effect of 5-HT is clearly mediated through activation of 5HT7 receptors. RT-PCR amplification and molecular cloning of the PCR product demonstrated the presence of 5-HT, mRNA in the rat adrenal gland. The occurrence of the 5-HT, protein in the rat adrenal cortex was demonstrated by Western blotting. Although S-HT is a potent stimulator of aldosterone secretion in various vertebrate species, the effects of 5-HT appear to be mediated by different receptor subtypes.
P12-3
Supported by INSERhf U413 and the Conseil Rbgional de HauteNormandie.
Membrane potential responses controlling K-induced backward swimming in Paramecium caudatum
S13-2
Oami K. and Takahashi M. Institute of Biological Sciences, University of Tsukuba, Tsukuba 305-8572, Japan. Paramecium
caudatum exhibits backward swimming in response to various external stimuli. To understand the mechanisms underlying the K-induced backward swimming in P. caudutum, we examined the membrane potential responses of the cells to an application of K-rich solution. Wild type and CNR mutant which does not show backward swimming were used in the experiments. In response to a rapid application of K-rich solution, wild type exhibited an initial action potential and a subsequent sustained membrane depolarization. CNR showed sustained depolarization but not action potentials. After termination of the application, CNR showed rapid repolarization while wild type showed prolongation of the depolarization persisting several seconds (depolarizing after potential). Ciliaxy reversal continued during the K-induced prolonged depolarization. Duration of the depolarizing after potential decreased as the duration of the application of the K-rich solution increased. It is concluded that the depolarizing after potential following the application of the K-rich solution represents the Ca conductance responsible for the K-induced backward swimming in Paramecium. The Ca conductance is activated by the K-rich solution and inactivated during the application.
GONADOTROPIN-RELEASING HORMONE: ARCHETYPE AND EVOLUTION Nancv M. Sherwood Department of Biology, University of Victoria, Victoria, B.C. Canada V8W 2Y2 Theprimarystructureof 14distinctformsofGnRHisknown Two of these forms have been isolated from a tunicate proving that invertebrates also have members of the GnRH family and showing the framework of the archetypical GnRH molecule. The original fun&m of G&H was apparently not the release of gonadotxopins from the pituitary gland as tuoicates predate the origin of the pituitary. A direct action of G&H UI the gonad both during early develcpment and in the adult tunicate have been suggested by initial studies.
During evolution GnRH is found as at least two distinct forms in individual brains not only in a single spies of tunicate, but also in most vertebrates including monkey and human
However, three forms of GnRH within a single brain arises in the earliest teleosts, the bony tongued fish Of the 14 GnRH peptides for which primary &ucture has been determined, the in& highly co&ed fo& of GnRH to date is a form first identified in c&kens and termed chicken Cc\G&H-II. This form of GnRH arose in the stem line that diverged to cartilaginous fish, bony fish and tetrapods. The structure and location of the neuron of cG&H-II synthesis in the midbrain
have not changed in evolution, &bough the ontological ori@
of the neuron& not clear. Some mar&A also appear to Gave t.hreefoxmsofGnRHinthebrain Inmonkevs.theseformsare mammalian GIN-I (LHRI-I), cGnRI-I-II and i third form in the lateral forebrain The distinct location of the three forms of GnRH in primate and fish brains suggests distinct funetiorx.
Symposium 13: Integrated control of brain-pituitary-peripheral axis. PolzoneM’ (Italy)
Chair: H. Habibi (Canada) and A.
Sugar-gated transduction ion channels localized in sensory processes of the insect taste cells Muraka and Kijima H Department of Physics, Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
We examined the activities of sugar-gated transduction ion channels on the sensory processes of taste receptor cells of the fleshfly, Boettcherisca prregr:rina, by the patch-clamp technique. Sensory processes of taste cells grew out from the cut end of the taste hair on a labellum isolated from a pupa in the fly Ringer solution. They were swollen into small spheres after Ca” was removed from the incubation solution. We could patch clamp these spheres and recorded sugar-induced responses in the whole-cell and outside-out configurations. In the whole-cell voltage-clamp condition, sugar-induced inward currents were observed in about l/3 of the sensory processes. The current amplitudes and their fluctuations were increased in a dose-dependent manner. The conductance showed about 0 mV
of the reversal potential, and was depressed by the external Ca”. Outside-out patches also contirmcd thcsc properties. WC could record single channel currents responding sucrose in some outside-out patches. The single channel conductance was about 40 pS, and their mean open time was less than 1 ms. These results indicate that the existence of a novel receptorchannel complex type transduction channel on the sensory process membrane of the sugar receptor cell, which is activated directly by sucrose without mediation by second messengers.
s13-1 Characterization of serotonergic and human adrenocortical cells.
receptors in frog, rat
Contesse V, Lenglet S, Lefebvre H, Kuhn JM, Delarue C and Vaudry H Eur. Inst. Pept. Res. (IFRMP 23), Lab. Cell. Mol. Neuroendocr., INSERM U413, UA CNRS, Univ. Rouen, 76821 Mt-St-Aignan, France. Serotonin (5-HT) is produced by different types of cells within the adrenal gland of various vertebrate species. In vitro studies have shown that 5-HT is a potent stimulator of corticosteroid secretion in frog, rat and human. The aim of the present study was to investigate the type of receptors mediating the corticotropic effect of S-HT in these three representative species. In both frog and human, .5-HT4 receptor agonists mimic the stimulatory effect of 5-HT while 5-HT4 receptor antagonists totally block the effect of 5-HT on corticosteroid secretion. In contrast, in the rat adrenal gland, the effect of 5-HT is clearly mediated through activation of 5HT7 receptors. RT-PCR amplification and molecular cloning of the PCR product demonstrated the presence of 5-HT, mRNA in the rat adrenal gland. The occurrence of the 5-HT, protein in the rat adrenal cortex was demonstrated by Western blotting. Although S-HT is a potent stimulator of aldosterone secretion in various vertebrate species, the effects of 5-HT appear to be mediated by different receptor subtypes.
P12-3
Supported by INSERhf U413 and the Conseil Rbgional de HauteNormandie.
Membrane potential responses controlling K-induced backward swimming in Paramecium caudatum
S13-2
Oami K. and Takahashi M. Institute of Biological Sciences, University of Tsukuba, Tsukuba 305-8572, Japan. Paramecium
caudatum exhibits backward swimming in response to various external stimuli. To understand the mechanisms underlying the K-induced backward swimming in P. caudutum, we examined the membrane potential responses of the cells to an application of K-rich solution. Wild type and CNR mutant which does not show backward swimming were used in the experiments. In response to a rapid application of K-rich solution, wild type exhibited an initial action potential and a subsequent sustained membrane depolarization. CNR showed sustained depolarization but not action potentials. After termination of the application, CNR showed rapid repolarization while wild type showed prolongation of the depolarization persisting several seconds (depolarizing after potential). Ciliaxy reversal continued during the K-induced prolonged depolarization. Duration of the depolarizing after potential decreased as the duration of the application of the K-rich solution increased. It is concluded that the depolarizing after potential following the application of the K-rich solution represents the Ca conductance responsible for the K-induced backward swimming in Paramecium. The Ca conductance is activated by the K-rich solution and inactivated during the application.
GONADOTROPIN-RELEASING HORMONE: ARCHETYPE AND EVOLUTION Nancv M. Sherwood Department of Biology, University of Victoria, Victoria, B.C. Canada V8W 2Y2 Theprimarystructureof 14distinctformsofGnRHisknown Two of these forms have been isolated from a tunicate proving that invertebrates also have members of the GnRH family and showing the framework of the archetypical GnRH molecule. The original fun&m of G&H was apparently not the release of gonadotxopins from the pituitary gland as tuoicates predate the origin of the pituitary. A direct action of G&H UI the gonad both during early develcpment and in the adult tunicate have been suggested by initial studies.
During evolution GnRH is found as at least two distinct forms in individual brains not only in a single spies of tunicate, but also in most vertebrates including monkey and human
However, three forms of GnRH within a single brain arises in the earliest teleosts, the bony tongued fish Of the 14 GnRH peptides for which primary &ucture has been determined, the in& highly co&ed fo& of GnRH to date is a form first identified in c&kens and termed chicken Cc\G&H-II. This form of GnRH arose in the stem line that diverged to cartilaginous fish, bony fish and tetrapods. The structure and location of the neuron of cG&H-II synthesis in the midbrain
have not changed in evolution, &bough the ontological ori@
of the neuron& not clear. Some mar&A also appear to Gave t.hreefoxmsofGnRHinthebrain Inmonkevs.theseformsare mammalian GIN-I (LHRI-I), cGnRI-I-II and i third form in the lateral forebrain The distinct location of the three forms of GnRH in primate and fish brains suggests distinct funetiorx.