Residual effects of focal brain ischaemia upon cannabinoid CB(1) receptor density and functionality in female rats

Adverse Social Experiences in Adolescent Rats Result in Enduring Effects on Social Competence, Pain Sensitivity and Endocannabinoid Signaling

Social affiliation is essential for many species and gains significant importance during adolescence. Disturbances in social affiliation, in particular social rejection experiences during adolescence, affect an individual’s well-being and are involved in the emergence of psychiatric disorders. The underlying mechanisms are still unknown, partly because of a lack of valid animal models. By using a novel animal model for social peer-rejection, which compromises adolescent rats in their ability to appropriately engage in playful activities, here we report on persistent impairments in social behavior and dysregulations in the endocannabinoid (eCB) system. From postnatal day (pd) 21 to pd 50 adolescent female Wistar rats were either reared with same-strain partners (control) or within a group of Fischer 344 rats (inadequate social rearing, ISR), previously shown to serve as inadequate play partners for the Wistar strain. Adult ISR animals showed pronounced deficits in social interaction, social memory, processing of socially transmitted information, and decreased pain sensitivity. Molecular analysis revealed increased CB1 receptor (CB1R) protein levels and CP55, 940 stimulated [³⁵S]GTPγS binding activity specifically in the amygdala and thalamus in previously peer-rejected rats. Along with these changes, increased levels of the eCB anandamide (AEA) and a corresponding decrease of its degrading enzyme fatty acid amide hydrolase (FAAH) were seen in the amygdala. Our data indicate lasting consequences in social behavior and pain sensitivity following peer-rejection in adolescent female rats. These behavioral impairments are accompanied by persistent alterations in CB1R signaling. Finally, we provide a novel translational approach to characterize neurobiological processes underlying social peer-rejection in adolescence.

Sex differences in brain proteomes of neuron-specific STAT3-null mice after cerebral ischemia/reperfusion

Signal transduction and activator of transcription-3 (STAT3) plays an important role in neuronal survival, regeneration and repair after brain injury. We previously demonstrated that STAT3 is activated in brain after cerebral ischemia specifically in neurons. The effect was sex-specific and modulated by sex steroids, with higher activation in females than males. In the current study, we used a proteomics approach to identify downstream proteins affected by ischemia in male and female wild-type (WT) and neuron-specific STAT3 knockout (KO) mice. We established four comparison groups based on the transgenic condition and the hemisphere analyzed, respectively. Moreover, the sexual variable was taken into account and male and female animals were analyzed independently. Results support a role for STAT3 in metabolic, synaptic, structural and transcriptional responses to cerebral ischemia, indeed the adaptive response to ischemia/reperfusion injury is delayed in neuronal-specific STAT3 KO mice. The differences observed between males and females emphasize the importance of sex-specific neuronal survival and repair mechanisms, especially those involving antioxidant and energy-related activities, often caused by sex hormones.

Lysophosphatidylinositol stimulates [³⁵S]GTPγS binding in the rat prefrontal cortex and hippocampus

Lysophosphatidylinositol (LPI) is a biologically active lipid that produces a number of responses in cultured cells, and has been suggested to have neuroprotective properties in vivo. Some of the actions of LPI are mediated by G-protein coupled receptors, but it is not known whether G-protein coupled receptor-mediated responses can be seen in intact brain tissue. In consequence, in the present study, we investigated autoradiographically whether LPI increased the [(35)S]GTPγS binding level in brain tissue slices. In standard assay conditions, where as a positive control a robust response to cannabinoid receptor activation by the agonist ligand CP55,940 was seen, there was no increase in the autoradiographic density over basal produced by LPI. However, when the conditions were modified (incubation at 4°C rather than at 25°C, incubation time increased to 3 h, GDP concentration reduced from 2 to 0.1 mM), a significant increase in [(35)S]GTPγS autoradiographic density in response to 10 μM LPI was seen in the prefrontal cortex, hippocampus, and cortex at the level of the hippocampus, although the degree of increase was small and very variable. No significant increases were seen in the hypothalamus or cerebellum. It is concluded that LPI, in the right conditions, can activate a sufficient number of G-proteins in the rat prefrontal cortex and hippocampus to produce a response in the [(35)S]GTPγS autoradiographic assay of G-protein coupled receptor function.