Mating-induced transient inhibition of responses to sex pheromone in a male moth is not mediated by octopamine or serotonin

In the male moth, Agrotis ipsilon, mating induces a transient inhibition of behavioural and central nervous responses to sex pheromone. Newly mated males are not attracted to sex pheromone, and the sensitivity of their antennal lobe (AL) neurons is lower than in virgin males. This rapid transient olfactory inhibition prevents them from re-mating unsuccessfully until they have refilled their sex glands. We hypothesized that this olfactory ‘switch off’ might be controlled by neuromodulators such as biogenic amines. To test our hypothesis, we studied the effects of octopamine (OA) and serotonin (5-hydroxytryptamine, 5-HT) on the coding properties of pheromone-sensitive AL neurons in virgin and newly mated males. We show that AL neuron sensitivity increased in newly mated males after injection of OA or 5-HT, but only OA treatment affected certain response characteristics of AL neurons in virgin males. Whereas all measured AL neuron response characteristics were different between virgin and newly mated males, amine treatment in newly mated males restored only the latency and spike frequency, but not the duration of excitatory and inhibitory phases, which were initially found in virgin males. Additionally, we investigated the behavioural effects of OA and 5-HT treatments in virgin and mated males. Although OA and 5-HT enhanced the general flight activity of newly mated males, amine treatments did not restore the behavioural pheromone response of mated moths. Altogether, these results show that, although biogenic amines modulate the olfactory system in moths, OA and 5-HT are probably not involved in the post-mating inhibition of responses to sex pheromone in A. ipsilon males.Fil: Barrozo, Romina. Institut National de la Recherche Agronomique; Francia. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Jarriault, David. Institut National de la Recherche Agronomique; FranciaFil: Simeone, Xenia. Institut National de la Recherche Agronomique; FranciaFil: Gaertner, Cyril. Institut National de la Recherche Agronomique; FranciaFil: Gadenne, Christophe. Institut National de la Recherche Agronomique; FranciaFil: Anton, Sylvia. Institut National de la Recherche Agronomique; Franci

α subunits in GABAA receptors are dispensable for GABA and diazepam action.

The major isoform of the GABAA receptor is α1β2γ2. The binding sites for the agonist GABA are located at the β2+/α1- subunit interfaces and the modulatory site for benzodiazepines at α1+/γ2-. In the absence of α1 subunits, a receptor was formed that was gated by GABA and modulated by diazepam similarly. This indicates that alternative subunits can take over the role of the α1 subunits. Point mutations were introduced in β2 or γ2 subunits at positions homologous to α1- benzodiazepine binding and GABA binding positions, respectively. From this mutation work we conclude that the site for GABA is located at a β2+/β2- subunit interface and that the diazepam site is located at the β2+/γ2- subunit interface. Computational docking leads to a structural hypothesis attributing this non-canonical interaction to a binding mode nearly identical with the one at the α1+/γ2- interface. Thus, the β2 subunit can take over the role of the α1 subunit for the formation of both sites, its minus side for the GABA binding site and its plus side for the diazepam binding site

The role of the nAChR subunits α5, β2, and β4 on synaptic transmission in the mouse superior cervical ganglion

Abstract Our previous immunoprecipitation analysis of nicotinic acetylcholine receptors (nAChRs) in the mouse superior cervical ganglion (SCG) revealed that approximately 55%, 24%, and 21% of receptors are comprised of α3β4, α3β4α5, and α3β4β2 subunits, respectively. Moreover, mice lacking β4 subunits do not express α5‐containing receptors but still express a small number of α3β2 receptors. Here, we investigated how synaptic transmission is affected in the SCG of α5β4‐KO and α5β2‐KO mice. Using an ex vivo SCG preparation, we stimulated the preganglionic cervical sympathetic trunk and measured compound action potentials (CAPs) in the postganglionic internal carotid nerve. We found that CAP amplitude was unaffected in α5β4‐KO and α5β2‐KO ganglia, whereas the stimulation threshold for eliciting CAPs was significantly higher in α5β4‐KO ganglia. Moreover, intracellular recordings in SCG neurons revealed no difference in EPSP amplitude. We also found that the ganglionic blocking agent hexamethonium was the most potent in α5β4‐KO ganglia (IC50: 22.1 μmol/L), followed by α5β2‐KO (IC50: 126.7 μmol/L) and WT ganglia (IC50: 389.2 μmol/L). Based on these data, we estimated an IC50 of 568.6 μmol/L for a receptor population consisting solely of α3β4α5 receptors; and we estimated that α3β4α5 receptors comprise 72% of nAChRs expressed in the mouse SCG. Similarly, by measuring the effects of hexamethonium on ACh‐induced currents in cultured SCG neurons, we found that α3β4α5 receptors comprise 63% of nAChRs. Thus, in contrast to our results obtained using immunoprecipitation, these data indicate that the majority of receptors at the cell surface of SCG neurons consist of α3β4α5

Scientific Reports / Molecular tools for GABAA receptors : High affinity ligands for 1-containing subtypes

-Aminobutyric acid type A (GABAA) receptors are pentameric GABA-gated chloride channels that are, in mammalians, drawn from a repertoire of 19 different genes, namely 1-6, 1-3, 1-3, , , , and 1-3. The existence of this wide variety of subunits as well as their diverse assembly into different subunit compositions result in miscellaneous receptor subtypes. In combination with the large number of known and putative allosteric binding sites, this leads to a highly complex pharmacology. Recently, a novel binding site at extracellular +/ interfaces was described as the site of modulatory action of several pyrazoloquinolinones. In this study we report a highly potent ligand from this class of compounds with pronounced 1-selectivity that mainly lacks -subunit selectivity. It constitutes the most potent 1-selective positive allosteric modulatory ligand with known binding site. In addition, a proof of concept pyrazoloquinolinone ligand lacking the additional high affinity interaction with the benzodiazepine binding site is presented. Ultimately, such ligands can be used as invaluable molecular tools for the detection of 1-containing receptor subtypes and the investigation of their abundance and distribution.(VLID)460736