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Aquatic insect species that leave the water after larval development, such as mayflies, have to deal with extremely different visual environments in their different life stages. Measuring the spectral sensitivity of the compound eyes of the virgin mayfly (Ephoron virgo) resulted in differences between the sensitivity of adults and larvae. Larvae were primarily green-, while adults were mostly UV-sensitive. The sensitivity of adults and larvae was the same in the UV, but in the green spectral range, adults were 3.3 times less sensitive than larvae. Transmittance spectrum measurements of larval skins covering the eye showed that the removal of exuvium during emergence cannot explain the spectral sensitivity change of the eyes. Taking numerous sky spectra from the literature, the ratio of UV and green photons in the skylight was shown to be maximal for θ ≈ −13° solar elevation, which is in the θmax = −14.7° and θmin = −7.1° typical range of swarming that was established from webcam images of real swarmings. We suggest that the spectral sensitivity of both the larval and adult eyes are adapted to the optical environment of the corresponding life stages.

Proper functioning of the nervous system is largely dependent on the precise regulation of the neuronal environment. By shielding the central nervous system (CNS) from potentially harmful substances, the blood-brain barrier (BBB) has an indispensable role in this process. The BBB is a specialized system of endothelial cells lining brain microvessels, which – supported by pericytes and glial cells – form a selective barrier between the blood and the neural tissue. Under abnormal conditions, permeability of the BBB may increase, which may either trigger or aggravate the disease. Since CNS disorders – at least in their initial phase – usually do not involve the whole brain and spinal cord, but are localized to a certain region, our aim was to understand whether the BBB is regionally heterogeneous at the molecular level. By using bioinformatics tools, we analyzed expression levels of genes specific to cerebral endothelial cells, pericytes or astrocytes in different brain territories. Our results revealed regional heterogeneities in the expression of BBB-associated genes in both human and mouse. Expression pattern of efflux transporters – which have a major role in blocking passage of therapeutic agents through the BBB – proved to be diverse both among brain regions and between mouse and human. Our results indicate that: (1) in silico database analyses are suitable for group-based studies on gene functions, overcoming the limitations of single-gene analyses; (2) high-throughput tests should always be validated using other methods; (3) when using animal models, inter-species differences have to be always considered; (4) when comparing different brain regions, the BBB is heterogeneous at the molecular level, and this might have clinical significance.

Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels and the Ih current they generate contribute to the pathophysiological mechanisms of absence seizures (ASs), but their precise role in neocortical and thalamic neuronal populations, the main components of the network underlying AS generation remains controversial. In diverse genetic AS models, Ih amplitude is smaller in neocortical neurons and either larger or unchanged in thalamocortical (TC) neurons compared to non-epileptic strains. A lower expression of neocortical HCN subtype 1 channels is present in genetic AS-prone rats and HCN2 Knock-Out mice exhibit ASs. Furthermore, whereas many studies have characterized Ih contribution to “absence-like” paroxysmal activity in vitro, no data is available on the specific role of cortical and thalamic HCN channels in behavioural seizures. Here, we show that the pharmacological block of HCN channels with the antagonist ZD7288 applied via reverse microdialysis in the ventrobasal thalamus (VB) of freely moving male Genetic Absence Epilepsy Rats from Strasbourg decreases TC neuron firing and abolishes spontaneous ASs. A similar effect is observed on γ-hydroxybutyric acid-elicited ASs in normal male Wistar rats. Moreover, thalamic knockdown of HCN channels via virally-delivered shRNA into the VB of male Stargazer mice, another genetic AS model, decreases spontaneous ASs and Ih-dependent electrophysiological properties of VB TC neurons. These findings provide the first evidence that block of TC neuron HCN channels prevents ASs and suggest that any potential anti-absence therapy that targets HCN channels should carefully consider the opposite role for cortical and thalamic Ih in the modulation of absence seizures., peer-reviewed