Key points• Dopamine D 1 receptors activate the cAMP/protein kinase A (PKA) pathway in both cortex and striatum, with different types of signalling enzymes being involved in cAMP/PKA signal integration. We investigated the functional implications of such differences.• Biosensor imaging in mouse brain slice preparations revealed that the cAMP/PKA signal increases faster, reaches higher levels and lasts longer in striatal neurones than in cortical neurones.• These differences result from faster cAMP production and lower degradation by type 4 phosphodiesterase activities in the striatum than in the cortex. In addition, DARPP-32 in the striatum prolongs the PKA response by inhibiting phosphatases.• These molecular features confers on striatal neurones a particular ability to temporally decode sub-second dopamine signals associated with reward and learning.Abstract The cAMP/protein kinase A (PKA) signalling cascade is ubiquitous, and each step in this cascade involves enzymes that are expressed in multiple isoforms. We investigated the effects of this diversity on the integration of the pathway in the target cell by comparing prefrontal cortical neurones with striatal neurones which express a very specific set of signalling proteins. The prefrontal cortex and striatum both receive dopaminergic inputs and we analysed the dynamics of the cAMP/PKA signal triggered by dopamine D 1 receptors in these two brain structures. Biosensor imaging in mouse brain slice preparations showed profound differences in the D 1 response between pyramidal cortical neurones and striatal medium spiny neurones: the cAMP/PKA response was much stronger, faster and longer lasting in striatal neurones than in pyramidal cortical neurones. We identified three molecular determinants underlying these differences: different activities of phosphodiesterases, particularly those of type 4, which strongly damp the cAMP signal in the cortex but not in the striatum; stronger adenylyl cyclase activity in the striatum, generating responses with a faster onset than in the cortex; and DARPP-32, a phosphatase inhibitor which prolongs PKA action in the striatum. Striatal neurones were also highly responsive in terms of gene expression since a single sub-second dopamine stimulation is sufficient to trigger c-Fos expression in the striatum, but not in the cortex. Our data show how L. R. V. Castro and M. Brito contributed equally to this work and are joint first authors.

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We investigate the effectiveness and safety of a novel magnetic hyperthermia (MHT) protocol, whereby a pretreatment with nontargeted magnetic nanoparticles (MNPs) is used to boost the subsequent iron loading of cancer cells by the targeted immuno-modified MNPs. As a model example, LN229 cancer cells express specific cell-surface receptors (CXCR4) at levels sufficient for diagnostic identification but insufficient for achieving 100% effective monotherapeutic MHT based on CXCR4-targeted MNPs. The nontargeted boost of the iron content overcomes this limitation of the targeted loading and is positively correlated with the maximum temperature reached during MHT treatment of LN229 cells. The effectiveness of the dual-population MHT strategy is validated by achieving a 100% lethal outcome for LN229 cancer cells 72 h after the treatment, while its safety is confirmed by the minimal cytotoxicity observed in control experiments with normal HK-2 cells or with an isotype-control targeting antibody. Systematic in vitro measurements thus demonstrate that the magnetic loading by targeted MNPs can be significantly increased by the nontargeted boost, even to double the iron concentration, while improving the effectiveness and maintaining the safety of MHT. This validation of the dual-population MHT strategy opens a novel materials-based pathway, unassisted by highly and nonselectively cytotoxic chemotherapeutic agents, to overcome the limited effectiveness of MHT for treating cancer cells that express only moderate levels of cell-surface receptors.

We demonstrate for the first time that an ultra-broadband 7 femtosecond (fs) fewcycle laser can be used for multicolor nonlinear imaging in a single channel detection geometry, when employing a time-resolved fluorescence detection scheme. On a multichromophore-labelled cell sample we show that the few-cycle laser can efficiently excite the multiple chromophores over a >400 nm two-photon absorption range. By combining the fewcycle laser excitation with time-correlated single-photon counting (TCSPC) detection to record two-photon fluorescence lifetime imaging microscopy (FLIM) images, the localization of different chromophores in the cell can be identified based on their fluorescence decay properties. The novel SyncRGB-FLIM multi-color bioimaging technique opens the possibility of real-time protein-protein interaction studies, where its single-scan operation translates into reduced laser exposure of the sample, resulting in more photoprotective conditions for biological specimens.