Search

Restrained honeybees can easily associate a sucrose reward to a metal plate. To study the role of nicotinic receptors in this learning, nicotinic antagonists (mecamylamine, MLA or α-bungarotoxin) or a NO-synthase inhibitor (L-NAME) were injected in haemolymph using doses leaving intact perception or motor functions. Mecamylamine impaired memory retrieval and single-trial learning without affecting long-term memory (LTM) formation that specifically occurs during multiple-trial learning. On the other hand, L-NAME, α- bungarotoxin and MLA only blocked LTM formation. This pharmacological dissociation indicates the existence of various functional types of nicotinic receptors. Those sensible to MLA and α-bungarotoxin could be coupled to NO-synthase., L'abeille en contention peut associer une récompense sucrée au scan antennaire d'une plaque métallique. Pour étudier le rôle des récepteurs nicotiniques dans cet apprentissage, des antagonistes nicotiniques (mécamylamine, MLA ou α-bungarotoxine) ou un inhibiteur de la NO-synthase (le L-NAME) ont été injectés dans l'hémolymphe à des doses sans effet sur la perception ou la motricité. La mécamylamine a bloqué le rappel de la trace mnésique et l'apprentissage en un essai sans affecter la formation de la mémoire à long terme (MLT) qui se produit spécifiquement durant l'apprentissage en plusieurs essais. Par contre, le L-NAME, l'α- bungarotoxine et le MLA ne bloquent que la formation de la MLT. Cette dissociation pharmacologique indique l'existence de plusieurs types fonctionnels de récepteurs nicotiniques. Ceux qui sont sensibles au MLA et à l'α-bungarotoxine seraient couplés à la NO-synthase.

The postsynaptic scaffolding A-kinase anchoring protein 79/150 (AKAP79/150) signaling complex regulates excitatory synaptic transmission and strength through tethering protein kinase A (PKA), PKC, and calcineurin (CaN) to the postsynaptic densities of neurons (Sanderson and Dell'Acqua, 2011), but its role in inhibitory synaptictransmission and plasticity is unknown. Using immunofluorescence and whole-cell patch-clamp recording in rat midbrain slices, we show that activation of postsynaptic D2 -like family of dopamine (DA) receptor in the ventral tegmental area (VTA) induces long-term depression (LTD) of GABAergic synapses on DA neurons through an inositol triphosphate receptor-mediated local rise in postsynaptic Ca2 and CaN activation accompanied by PKA inhibition, which requires AKAP150 as a bridging signaling molecule. Our data also illuminate a requirement for a clathrin-mediated internalization of GABAA receptors in expression of LTDGABA. Moreover, disruption of AKAP-PKA anchoring does not affect glutamatergic synapses onto DA neurons, suggesting that the PKA-AKAP-CaN complex is uniquely situated at GABAA receptor synapses in VTA DA neurons to regulate plasticity associated with GABAA receptors. Drug-induced modulation of GABAergic plasticity in the VTA through such novel signaling mechanisms has the potential to persistently alter the output of individual DA neurons and of the VTA, which may contribute to the reinforcing or addictive properties of drugs of abuse.

International audience; Invertebrate Physiology, a section of the journal Frontiers in Physiology Adult moths need energy and nutrients for reproducing and obtain them mainly by consuming flower nectar (a solution of sugars and other compounds). Gustatory perception gives them information on the plants they feed on. Feeding and food perception are integrated in the proboscis extension response, which occurs when their antennae touch a sugar solution. We took advantage of this reflex to explore moth sugar responsiveness depending on different parameters (i.e., sex, age, satiety, site of presentation, and composition of the solution). We observed that starvation but not age induced higher response rates to sucrose. Presentation of sucrose solutions in a randomized order confirmed that repeated sugar stimulations did not affect the response rate; however, animals were sometimes sensitized to water, indicating sucrose presentation might induce non-associative plasticity. Leg stimulation was much less efficient than antennal stimulation to elicit a response. Quinine prevented and terminated sucrose-elicited proboscis extension. Males but not females responded slightly more to sucrose than to fructose. Animals of either sex rarely reacted to glucose, but curiously, mixtures in which half sucrose or fructose were replaced by glucose elicited the same response rate than sucrose or fructose alone. Fructose synergized the response when mixed with sucrose in male but not female moths. This is consistent with the fact that nectars consumed by moths in nature are mixtures of these three sugars, which suggests an adaptation to nectar perception.