Effects of dormant vs. growing season burns on small mammal captures at Cooper Farm in Muncie, Indiana

Prescribed burning is an important method for maintaining tall-grass prairies. Done in the growing season (late summer) or the dormant season (late fall or early spring), burning alters nutrient cycling and clears dead plant material from the prairie. Due to the different plant types promoted by each burn type, growing and dormant season burns have different effects on small mammal species composition This objective of this study was to determine differences in small mammal captures in prairie plots subjected to growing season burns and prairie plots subjected to dormant season burns. Small mammals were captured at Cooper Farm from September 2nd until November 6th, 2014 in 10 three-day trapping sessions with a total of 2,000 trap nights. Fifty Sherman traps were set in grid formations in two systematically selected prairie plots per trapping session. A two-sample t-test revealed that there was no difference in number of captures between growing and dormant season burn plots. This is the beginning of a long-term study; future studies may better see the long-term effects of the burns. The long-term effects of the burns may change number of captures, better reflecting importance of burn type on small mammal communities. Also any changes in study design that would increase trap success, such as lengthening the trapping season and number of trap nights would improve the accuracy of the results and better reflect the effects of burn type on small mammals.Honors CollegeThesis (B.?

Neuroprotective effects of the cannabinoid agonist HU210 on retinal degeneration

Cannabinoids have been demonstrated to exert neuroprotective effects on different types of neuronal insults. Here we have addressed the therapeutic potential of the synthetic cannabinoid HU210 on photoreceptor degeneration, synaptic connectivity and functional activity of the retina in the transgenic P23H rat, an animal model for autosomal dominant retinitis pigmentosa (RP). In P23H rats administered with HU210 (100 μg/kg, i.p.) from P24 to P90, ERG recordings showed an amelioration of vision loss, as compared to vehicle-administered animals. Under scotopic conditions, the maximum a-wave amplitudes recorded at P60 and P90 were higher in HU210-treated animals, as compared to the values obtained in untreated animals. The scotopic b-waves were significantly higher in treated animals than in untreated rats at P30, P60 and P90. This attenuation of visual deterioration correlated with a delay in photoreceptor degeneration and the preservation of retinal cytoarchitecture. HU210-treated animals had 40% more photoreceptors than untreated animals. Presynaptic and postsynaptic elements, as well as the synaptic contacts between photoreceptors and bipolar or horizontal cells, were also preserved in HU210-treated P23H rats. These results indicate that HU210 preserves cone and rod structure and function, together with their contacts with postsynaptic neurons, in P23H rats. These data suggest that cannabinoids are potentially useful to delay retinal degeneration in RP patients.This research was supported by grants from the Spanish Ministry of Economy and Competitiveness (BFU2012-36845-FEDER), Instituto de Salud Carlos III (RETICS RD12/0034/0010), Universidad de Alicante (UA2010-48536273), and the Organización Nacional de Ciegos Españoles (ONCE)

A biophysical model of endocannabinoid-mediated short term depression in hippocampal inhibition

Memories are believed to be represented in the synaptic pathways of vastly interconnected networks of neurons. The plasticity of synapses, that is, their strengthening and weakening depending on neuronal activity, is believed to be the basis of learning and establishing memories. An increasing number of studies indicate that endocannabinoids have a widespread action on brain function through modulation of synap–tic transmission and plasticity. Recent experimental studies have characterised the role of endocannabinoids in mediating both short- and long-term synaptic plasticity in various brain regions including the hippocampus, a brain region strongly associated with cognitive functions, such as learning and memory. Here, we present a biophysically plausible model of cannabinoid retrograde signalling at the synaptic level and investigate how this signalling mediates depolarisation induced suppression of inhibition (DSI), a prominent form of shortterm synaptic depression in inhibitory transmission in hippocampus. The model successfully captures many of the key characteristics of DSI in the hippocampus, as observed experimentally, with a minimal yet sufficient mathematical description of the major signalling molecules and cascades involved. More specifically, this model serves as a framework to test hypotheses on the factors determining the variability of DSI and investigate under which conditions it can be evoked. The model reveals the frequency and duration bands in which the post-synaptic cell can be sufficiently stimulated to elicit DSI. Moreover, the model provides key insights on how the state of the inhibitory cell modulates DSI according to its firing rate and relative timing to the post-synaptic activation. Thus, it provides concrete suggestions to further investigate experimentally how DSI modulates and is modulated by neuronal activity in the brain. Importantly, this model serves as a stepping stone for future deciphering of the role of endocannabinoids in synaptic transmission as a feedback mechanism both at synaptic and network level

Cannabinoid-mediated short-term plasticity in hippocampus

Endocannabinoids modulate both excitatory and inhibitory neurotransmission in hippocampus via activation of pre-synaptic cannabinoid receptors. Here, we present a model for cannabinoid mediated short-term depression of excitation (DSE) based on our recently developed model for the equivalent phenomenon of suppressing inhibition (DSI). Furthermore, we derive a simplified formulation of the calcium-mediated endocannabinoid synthesis that underlies short-term modulation of neurotransmission in hippocampus. The simplified model describes cannabinoid-mediated short-term modulation of both hippocampal inhibition and excitation and is ideally suited for large network studies. Moreover, the implementation of the simplified DSI/DSE model provides predictions on how both phenomena are modulated by the magnitude of the pre-synaptic cell's activity. In addition we demonstrate the role of DSE in shaping the post-synaptic cell's firing behaviour qualitatively and quantitatively in dependence on eCB availability and the pre-synaptic cell's activity. Finally, we explore under which conditions the combination of DSI and DSE can temporarily shift the fine balance between excitation and inhibition. This highlights a mechanism by which eCBs might act in a neuro-protective manner during high neural activity

CB1 Receptor Negative Allosteric Modulators as a Potential Tool to Reverse Cannabinoid Toxicity

Peer reviewe

Cannabinoid CB2R receptors are upregulated with corneal injury and regulate the course of corneal wound healing

CB2R receptors have demonstrated beneficial effects in wound healing in several models. We therefore investigated a potential role of CB2R receptors in corneal wound healing. We examined the functional contribution of CB2R receptors to the course of wound closure in an in vivo murine model. We additionally examined corneal expression of CB2R receptors in mouse and the consequences of their activation on cellular signaling, migration and proliferation in cultured bovine corneal epithelial cells (CECs). Using a novel mouse model, we provide evidence that corneal injury increases CB2R receptor expression in cornea. The CB2R agonist JWH133 induces chemorepulsion in cultured bovine CECs but does not alter CEC proliferation. The signaling profile of CB2R activation is activating MAPK and increasing cAMP accumulation, the latter perhaps due to Gs -coupling. Lipidomic analysis in bovine cornea shows a rise in acylethanolamines including the endocannabinoid anandamide 1 hour after injury. In vivo, CB2R deletion and pharmacological block result in a delayed course of wound closure. In summary, we find evidence that CB2R receptor promoter activity is increased by corneal injury and that these receptors are required for the normal course of wound closure, possibly via chemorepulsion.post-print1,81 M

Revisiting cannabinoid receptor 2 expression and function in murine retina.

The cannabinoid receptor CB2 plays a significant role in the regulation of immune function whereas neuronal expression remains a subject of contention. Multiple studies have described CB2 in retina and a recent study showed that CB2 deletion altered retinal visual processing. We revisited CB2 expression using immunohistochemistry and a recently developed CB2-eGFP reporter mouse. We examined the consequence of acute vs. prolonged CB2 deactivation on the electroretinogram (ERG) responses. We also examined lipidomics in CB2 knockout mice and potential changes in microglia using Scholl analysis. Consistent with a published report, in CB2 receptor knockout mice see an increased ERG scotopic a-wave, as well as stronger responses in dark adapted cone-driven ON bipolar cells and, to a lesser extent cone-driven ON bipolar cells early in light adaptation. Significantly, however, acute block with CB2 antagonist, AM630, did not mimic the results observed in the CB2 knockout mice whereas chronic (7 days) block did. Immunohistochemical studies show no CB2 in retina under non-pathological conditions, even with published antibodies. Retinal CB2–eGFP reporter signal is minimal under baseline conditions but upregulated by intraocular injection of either LPS or carrageenan. CB2 knockout mice see modest declines in a broad spectrum of cannabinoid-related lipids. The numbers and morphology of microglia were unaltered. In summary minimal CB2 expression is seen in healthy retina. CB2 appears to be upregulated under pathological conditions. Previously reported functional consequences of CB2 deletion are an adaptive response to prolonged blockade of these receptors. CB2 therefore impacts retinal signaling but perhaps in an indirect, potentially extra-ocular fashion.post-print8285 K

Evidence that cannabinoid CB1 receptors regulate intraocular pressure via two opposing mechanisms

The cannabinoid signaling system regulates intraocular pressure (IOP) in the mouse via a complex system that includes three receptors: CB1, GPR18 and GPR119. In each case, activating the receptor lowers IOP, but CB1 receptors are found both at sites of aqueous humor inflow and outflow. As such, knockout mice for any of these receptors would be expected to have higher-than average, or at least unchanged, intraocular pressure. The current study investigates the unexpected observation that CB1 knockout mice have lower pressure than wild type counterparts by testing various regulators of cannabinoid signaling in murine models of IOP. We now report that a CB1 antagonist has differential effects on IOP: SR141716 raises IOP in standard light cycle (SLC) but lowers IOP in reverse light cycle (RLC). This is mimicked by ABD1085, a negative allosteric modulator of CB1. CB1 inhibitors lower IOP in both normotensive and hypertensive mouse eyes. The pressure-lowering effect is absent in CB1 knockout mice. IOP rebounds after the end of treatment but shows no sign of desensitization with daily treatment for a week. Unlike the positive cannabinoid effect, antagonist effects are not sex-dependent. We propose that there are two mechanisms of action for CB1, one that lowers IOP upon activation and a second with inverse sign that lowers IOP when CB1 is antagonized. The relatively lower pressure in CB1 knockout mouse eyes suggests that this second negative regulation of IOP is dominant

Discovery of Prostamide F2α and Its Role in Inflammatory Pain and Dorsal Horn Nociceptive Neuron Hyperexcitability

It was suggested that endocannabinoids are metabolized by cyclooxygenase (COX)-2 in the spinal cord of rats with kaolin/λ-carrageenan-induced knee inflammation, and that this mechanism contributes to the analgesic effects of COX-2 inhibitors in this experimental model. We report the development of a specific method for the identification of endocannabinoid COX-2 metabolites, its application to measure the levels of these compounds in tissues, and the finding of prostamide F2α (PMF2α) in mice with knee inflammation. Whereas the levels of spinal endocannabinoids were not significantly altered by kaolin/λ-carrageenan-induced knee inflammation, those of the COX-2 metabolite of AEA, PMF2α, were strongly elevated. The formation of PMF2α was reduced by indomethacin (a non-selective COX inhibitor), NS-398 (a selective COX-2 inhibitor) and SC-560 (a selective COX-1 inhibitor). In healthy mice, spinal application of PMF2α increased the firing of nociceptive (NS) neurons, and correspondingly reduced the threshold of paw withdrawal latency (PWL). These effects were attenuated by the PMF2α receptor antagonist AGN211336, but not by the FP receptor antagonist AL8810. Also prostaglandin F2α increased NS neuron firing and reduced the threshold of PWL in healthy mice, and these effects were antagonized by AL8810, and not by AGN211336. In mice with kaolin/λ-carrageenan-induced knee inflammation, AGN211336, but not AL8810, reduced the inflammation-induced NS neuron firing and reduction of PWL. These findings suggest that inflammation-induced, and prostanoid-mediated, enhancement of dorsal horn NS neuron firing stimulates the production of spinal PMF2α, which in turn contributes to further NS neuron firing and pain transmission by activating specific receptors