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The osmolarity of the extracellular space (ECS) compartment is an important factor determining the excitability of neuronal tissue. In the adult hippocampus an important role of osmolarity and ECS diffusion parameters on the susceptibility to epileptic events is well established, but the influence of hypo- and hyperosmolar conditions on the immature hippocampus remains elusive. To investigate the influence of osmolarity on epileptiform activity, extracellular field potentials were recorded in the CA3 region of hippocampal slices of immature (postnatal days 4-7) Wistar rats. The ECS diffusion parameters were determined by the real-time tetramethylammonium (TMA+) iontophoretic method with ion-selective microelectrodes in immature hippocampal slices and showed a lack of diffusion anisotropy; a tortuosity of about 1.39; and a volume fraction, alpha, of 0.41 +/- 0.01 (n = 10 slices). A reduction in osmolarity of -90 mOsm induced a decrease in alpha to 0.17 +/- 0.02 (n = 4 slices). The frequency of epileptiform activity elicited in 10-50 microM 4-AP-containing low-Mg2+ solution was increased under -90 mOsm and -40 mOsm hypoosmolar conditions by 39.9% +/- 8.1% (n = 16) and 24.1% +/- 4.8% (n = 10), respectively, whereas hyperosmolar solutions decreased the frequency. A -90-mOsm reduction in the osmolarity of low-Mg2+ solution induced epileptiform activity in nine of 19 slices. In summary, these results demonstrate that hypoosmolar conditions increased excitability and susceptibility to epileptiform activity in immature hippocampal slices, suggesting a functional role of the larger alpha in suppression of seizures.

In recent environmental research, relational values (RVs) have emerged as a new group of values to explain environmental behavior. Although this new concept is attracting attention, empirical studies on the subject are still rare. On this basis, we have conducted three studies to analyze an existing measurement tool for RVs and compared the construct with the concept of connection to nature. In study 1, we confirmed convergent and discriminant validity of the RV scale by comparing it with the Two Factor Model of Environmental Values (2-MEV) model using a sample of n = 350 university students. Additionally, study 1 verified reliability using test-retest reliability on three different groups of students (n 1 = 53; n 2 = 37; n 3 = 48). In study 2, principal component analyses were performed to examine the structure of RVs and to compare it to the concept of connection to nature by reusing the sample 350 university students from study 1. The results show that RVs and connection to nature are not fundamentally distinct constructs, but overlap. However, if the structure of the RV measurement is forced to a single factor, no perfect fit is found, making a multidimensional solution more likely. A third study was conducted to review the results from study 2 using confirmatory factor analysis on a new sample of 878 university and high school students. Study 3 confirmed RVs as a multidimensional construct with three factors: care, community, and connection. It also proved the overlap of the connection to nature and RV concepts to some extent. Keywords: relational values, connectedness to nature, connectedness to nature scale, scale validation, environmental behavior, two factor model of environmental values model Frontiers in Psychology | www.frontiersin.org Frontiers in Psychology | www.frontiersin.org

SUMMARYPurpose: Despite the consistent observation that c-aminobutyric acid A (GABA A ) receptors mediate excitatory responses at perinatal stages, the role of the GABAergic system in the generation of neonatal epileptiform activity remains controversial. Therefore, we analyzed whether tonic and phasic GABAergic transmission had differential effects on neuronal excitability during early development. Methods: We performed whole cell patch-clamp and field potential recordings in the CA3 region of hippocampal slices from immature (postnatal day 4-7) rats to analyze the effect of specific antagonists and modulators of tonic and phasic GABAergic components on neuronal excitability. Key Findings: The GABAergic antagonists gabazine (3 lM) and picrotoxin (100 lM) induced epileptiform discharges, whereas activation of GABA A receptors attenuated epileptiform discharges. Under low-Mg 2+ conditions, 100 nM gabazine and 1 lM picrotoxin were sufficient to provoke epileptiform activity in 63.2% (n = 19) and 53.8% (n = 26) of the slices, respectively. Whole-cell patchclamp experiments revealed that these concentrations significantly reduced the amplitude of phasic GABAergic postsynaptic currents but had no effect on tonic currents. In contrast, 1-lM 4,5,6,7-tetrahydroisoxaz-olo[5,4-c]-pyridin-3-ol (THIP) induced a tonic current of )12 ± 2.5 pA (n = 6) and provoked epileptiform discharges in 57% (n = 21) of the slices. Significance: We conclude from these results that in the early postnatal rat hippocampus a constant phasic synaptic activity is required to control excitability and prevent epileptiform activity, whereas tonic GABAergic currents can mediate excitatory responses. Pharmacologic intervention at comparable human developmental stages should consider these ambivalent GABAergic actions.