Monosynaptic retrograde tracing of neurons expressing the G-protein coupled receptor Gpr151 in the mouse brain.

GPR151 is a G-protein coupled receptor for which the endogenous ligand remains unknown. In the nervous system of vertebrates, its expression is enriched in specific diencephalic structures, where the highest levels are observed in the habenular area. The habenula has been implicated in a range of different functions including behavioral flexibility, decision making, inhibitory control, and pain processing, which makes it a promising target for treating psychiatric and neurological disease. This study aimed to further characterize neurons expressing the Gpr151 gene, by tracing the afferent connectivity of this diencephalic cell population. Using pseudotyped rabies virus in a transgenic Gpr151-Cre mouse line, monosynaptic afferents of habenular and thalamic Gpr151-expressing neuronal populations could be visualized. The habenular and thalamic Gpr151 systems displayed both shared and distinct connectivity patterns. The habenular neurons primarily received input from basal forebrain structures, the bed nucleus of stria terminalis, the lateral preoptic area, the entopeduncular nucleus, and the lateral hypothalamic area. The Gpr151-expressing neurons in the paraventricular nucleus of the thalamus was primarily contacted by medial hypothalamic areas as well as the zona incerta and projected to specific forebrain areas such as the prelimbic cortex and the accumbens nucleus. Gpr151 mRNA was also detected at low levels in the lateral posterior thalamic nucleus which received input from areas associated with visual processing, including the superior colliculus, zona incerta, and the visual and retrosplenial cortices. Knowledge about the connectivity of Gpr151-expressing neurons will facilitate the interpretation of future functional studies of this receptor.

Systematic evaluation of skeletal fractures caused by induction of electroconvulsive seizures in rat state a need for attention and refinement of the procedure.

OBJECTIVE: Electroconvulsive therapy (ECT) is one of the most efficient treatments for major depression. Electroconvulsive seizures (ECS), the animal model of ECT, is widely used to study both mechanisms of action and adverse effects of ECT. As the treatment itself serves as an instant anaesthetic and anaesthetic agents may affect memory functions and behaviour, ECS is traditionally administered without muscle relaxation and anaesthesia. A major problem of unmodified ECS, which has only been addressed peripherally in the literature, is that some animals sustain spinal fractures and subsequent hind leg paralysis (paraplegia). This phenomenon leads to a higher degree of suffering and these animals need to be excluded from the studies. To reach sufficient statistical power, the group sizes are therefore often increased and this may lead to a pre-selected study group in risk of skewing the results. Moreover, the study design of the experiments do not comply with the 3R principles, which advocate for both refinement and reduction of animal experiments. The objective of this study is to systematically evaluate injuries caused by ECS. METHODS: We summarise the incidence of spinal fractures from 24 studies conducted during 2009-2015 in six different rat strains and report preliminary findings on scapular fractures following auricular ECS. RESULTS: In total, 12.8% of all tested animals suffered from spinal fractures and we find an increase in spinal fracture incidence over time. Furthermore, X-ray analyses revealed that some animals displayed scapular fractures. CONCLUSION: We discuss consequences of and possible explanations for ECS-induced fractures. Modifications of the method are highly warranted and we furthermore suggest that all animals are thoroughly examined for discrete fractures.

Effect of electroconvulsive seizures on cognitive flexibility.

Electroconvulsive seizures (ECS), an animal model of electroconvulsive therapy, strongly stimulate hippocampal neurogenesis, but it is not known how this relates to the therapeutic effect or to the unwanted cognitive side effects. Recent findings suggest that neurogenesis might be important for flexible learning in changing environments. We hypothesize that animals receiving ECS treatment, which induces hippocampal neurogenesis, will show enhanced cognitive flexibility compared with controls. We have utilized a touch screen-based cognitive test (location discrimination (LD) task) to assess how five consecutive ECS treatments affect cognitive flexibility (measured as reversal of cognitive strategy) as well as spatial pattern separation ability. ECS-treated animals performed more reversals in the LD task earlier than controls over the 9 experimental weeks irrespective of spatial separation of visual stimuli, indicating an enhanced cognitive flexibility but unaffected pattern separation ability after ECS. We observed no correlation between hippocampal neurogenesis and the number of performed reversals during the last experimental week. This is the first study to elucidate the effect of ECS on cognitive flexibility. Our results indicate that ECS improves cognitive flexibility without affecting spatial pattern separation ability. Whether cognitive flexibility is enhanced via neurogenesis or other ECS-modulated processes, remains unknown. © 2016 Wiley Periodicals, Inc.

Effect of electroconvulsive seizures on pattern separation.

Strategies employing different techniques to inhibit or stimulate neurogenesis have implicated a role for adult-born neurons in the therapeutic effect of antidepressant drugs, as well as a role in memory formation. Electroconvulsive seizures (ECS), an animal model of electroconvulsive therapy, robustly stimulate hippocampal neurogenesis, but it is not known how this relates to either therapeutic efficacy or unwanted cognitive side effects. We hypothesized that the ECS-derived increase in adult-born neurons would manifest in improved pattern separation ability, a memory function that is believed to be both hippocampus-dependent and coupled to neurogenesis. To test this hypothesis, we stimulated neurogenesis in adult rats by treating them with a series of ECS and compared their performances in a trial-unique delayed nonmatching-to-location task (TUNL) to a control group. TUNL performance was analyzed over a 12-week period, during which newly formed neurons differentiate and become functionally integrated in the hippocampal neurocircuitry. Task difficulty was manipulated by modifying the delay between sample and choice, and by varying the spatial similarity between target and distracter location. Although animals learned the task and improved the number of correct responses over time, ECS did not influence spatial pattern separation ability.