The effect of P2X7 antagonism on subcortical spread of optogenetically-triggered cortical spreading depression and neuroinflammation.

Migraine is a neurological disorder characterized by episodes of severe headache. Cortical spreading depression (CSD), the electrophysiological equivalent of migraine aura, results in opening of pannexin 1 megachannels that release ATP and triggers parenchymal neuroinflammatory signaling cascade in the cortex. Migraine symptoms suggesting subcortical dysfunction bring subcortical spread of CSD under the light. Here, we investigated the role of purinergic P2X7 receptors on the subcortical spread of CSD and its consequent neuroinflammation using a potent and selective P2X7R antagonist, JNJ-47965567. P2X7R antagonism had no effect on the CSD threshold and characteristics but increased the latency to hypothalamic voltage deflection following CSD suggesting that ATP acts as a mediator in the subcortical spread. P2X7R antagonism also prevented cortical and subcortical neuronal activation following CSD, revealed by bilateral decrease in c-fos positive neuron count, and halted CSD-induced neuroinflammation revealed by decreased neuronal HMGB1 release and decreased nuclear translocation of NF-kappa B-p65 in astrocytes. In conclusion, our data suggest that P2X7R plays a role in CSD-induced neuroinflammation, subcortical spread of CSD and CSD-induced neuronal activation hence can be a potential target.

The Effect of Inhibition of Perisynaptic Astrocyte Glycogen Utilization on Depression-Like Behavior. / Sinaptik Enerji Kaynagi Glikojenin Kullaniminin Engellenmesinin Depresyon-benzeri Davranislara Etkisi.

OBJECTIVE: Under physiological conditions, astrocytes produce lactate to meet the increased synaptic energy demand due to neuronal activity. In the light of the findings showing that this process is disrupted in the pathophysiology of major depression, the aim of this study is to investigate the effect of pharmacological inhibition of perisynaptic astrocyte glycogen utilization on anxiety-like behavior and depression-like behavior in female and male mice. METHODS: In this study, DAB (1,4-dideoxy-1,4-imino-D-arabinitol), which is an inhibitor of glycogen breaking enzyme glycogen phosphorylase, was intrahippocampally administered to 15 female and 14 male Swiss albino mice, while 15 female and 12 male Swiss albino mice received intrahippocampal saline injections. Three and five days after the injections, the anxiety-like and depression-like behaviors of the mice were assessed by locomotor activity, open-field test, light-dark box test, tail suspension test and sucrose preference test. RESULTS: Three days after injection, neither depression-like nor anxietylike significant behavioral changes were detected in the male experimental group mice compared to the control group; but an increase in locomotor activity (p=0.05) and time spent in the open-field (p=0.01) were observed on the fifth day. In evaluations of the female experimental group mice on the third and fifth days, depression-like and anxiety-like behaviors were found similar to the control group, as seen in the male mice. The only significant difference in the experimental group female mice was found in the sucrose preference test, which revealed an increased tendency to prefer sucrose (p=0.003) compared to the control group. CONCLUSION: The inhibition of glycogen use in the hippocampus by DAB did not affect anxiety-like and depression-like behaviors 3 and 5 days after injection in both female and male mice. The increase in the time spent in the open-field by male experimental group mice was associated not with anxiety, but with increase in the locomotor activity. The fact that no significant difference was observed in the light-dark box test, which is another test used to evaluate anxiety, supported this opinion. The increase seen in the sucrose preference test in female experimental group mice was not interpreted as an increase in hedonic behavior because prevention of glycogen breakdown in the hypothalamus might have homeostatically increased sugar-craving and therefore resulted in an increase in sucrose preference. Different set of tests better targeting the energy and glucose metabolism and applied at farther time points than surgery are recommended for future studies.

Repeated Collection of Vaginal Smear Causes Stress in Mice.

Introduction: Women are more likely to be misdiagnosed in many neuropsychiatric disorders than men. One of the possible underlying reasons for this disparity may be more frequent use of male mice than female mice in neuroscience studies. With the increasing realization of the shortcomings of this approach in understanding the neurobiological basis of these disorders, many funding agencies mandate the inclusion of both male and female subjects in study design. As the behaviors vary with the stage of the estrous cycle, the collection of vaginal smears to identify the estrous stage becomes a widely used procedure. Here we tested whether vaginal smear collection causes similar effects to that of stress by evaluating an increase in depression-like behavior and impairment in memory. Method: Vaginal smear was collected from Swiss albino mice twice a day for 10 days. In order to test depression-like behavior tail suspension, sucrose preference and splash tests were conducted. Novel object recognition and novel object location tests were performed 1 hour and 24 hours after training to evaluate short-and long-term memory respectively. Results: The female mice whose vaginal smears were collected demonstrated increased behavioral despair and anhedonia. Vaginal smear group showed deficits in both short-term and long-term memory when compared to the control group. Conclusion: Our results indicate that the collection of vaginal smear not only increased depression-like behaviors in mice, but also impaired short-term and long-term memory, indicating that the procedure of vaginal smear collection was stressful. We recommend to consider other ways of estrous cycle staging when studying behavior.

Striatal Neurotransmitter Release-related Presynaptic Proteins in L-dopa Induced Dyskinesia in a Model of Parkinsonism.

INTRODUCTION: In Parkinson's disease, L-dopa-induced dyskinesia (LID) and motor fluctuations incapacitate patients as much as the disease itself. Many studies demonstrated that postsynaptic alterations and striatal synaptic plasticity changes play a role in LID development. Here, we aimed to study the role of striatal presynaptic proteins in LID pathogenesis. METHODS: For this purpose, 6-hydroxydopamine model of parkinsonism was used. To induce LID, these rats were treated with intraperitoneal injections of L-dopa 25 mg/kg with benserazide 6.25 mg/kg b.i.d for 21 days. Rats with parkinsonism treated with saline and control rats treated with saline or L-dopa/ benserazide were also included. Behaviors of rats were videotaped and scored according to dyskinesia scale. Striatal tissue was analysed with immunofluorescence staining and immunoblotting to confirm loss of tyrosine hydroxylase (TH) expression due to dopaminergic denervation and to explore the alterations in the expression of presynaptic proteins, secretogranin 2 (SG2), synaptophysin (Syp) and synaptotagmin 7 (Syt7). RESULT: LID developed only in rats with parkinsonism treated with chronic L-dopa. Immunofluorescence and immunoblotting studies for TH confirmed depletion of dopaminergic neurons, which was also strongly and negatively correlated with severity of LID. Striatal SG2 and Syp levels were found increased in parkinsonian rats. Chronic L-dopa treatment further increased SG2 levels in denervated striatum. Striatal SG 2 level showed a significant moderate, positive correlation with LID severity. Immunofluorescence studies also demonstrated increased expression of these presynaptic proteins in the denervated striatum. CONCLUSION: As, severity of LID was clearly correlated with striatal SG2 expression; there is supposedly a functional relationship between striatal SG2 and LID. Further studies are needed to find out molecular mechanisms linking increased SG2 expression and LID.