Involvement of nicotinergic mechanisms in thyrotropin-releasing hormone-induced neurologic recovery after concussive head injury in the mouse

A Systematic Review of Closed Head Injury Models of Mild Traumatic Brain Injury in Mice and Rats

Mild TBI (mTBI) is a significant health concern. Animal models of mTBI are essential for understanding mechanisms, and pathological outcomes, as well as to test therapeutic interventions. A variety of closed head models of mTBI that incorporate different aspects (i.e., biomechanics) of the mTBI have been reported. The aim of the current review was to compile a comprehensive list of the closed head mTBI rodent models, along with the common data elements, and outcomes, with the goal to summarize the current state of the field. Publications were identified from a search of PubMed and Web of Science and screened for eligibility following PRISMA guidelines. Articles were included that were closed head injuries in which the authors classified the injury as mild in rats or mice. Injury model and animal-specific common data elements, as well as behavioral and histological outcomes, were collected and compiled from a total of 402 articles. Our results outline the wide variety of methods used to model mTBI. We also discovered that female rodents and both young and aged animals are under-represented in experimental mTBI studies. Our findings will aid in providing context comparing the injury models and provide a starting point for the selection of the most appropriate model of mTBI to address a specific hypothesis. We believe this review will be a useful starting place for determining what has been done and what knowledge is missing in the field to reduce the burden of mTBI.

S 17092: a prolyl endopeptidase inhibitor as a potential therapeutic drug for memory impairment. Preclinical and clinical studies

Any treatment that could positively modulate central neuropeptides levels would provide a promising therapeutic approach to the treatment of cognitive deficits associated with aging and/or neurodegenerative diseases. Therefore, based on the activity in rodents, S 17092 (2S,3aS,7aS)-1][(R,R)-2-phenylcyclopropyl]carbonyl]-2-[(thiazolidin-3-yl)carbonyl]octahydro-1H-indole) has been selected as a potent inhibitor of cerebral prolyl-endopeptidase (PEP). By retarding the degradation of neuroactive peptides, S 17092 was successfully used in a variety of memory tasks. These tasks explored short-term, long-term, reference and working memory in aged mice, as well as in rodents and monkeys with chemically induced amnesia or spontaneous memory deficits. S 17092 has also been safely administered to humans, and showed a clear peripheral expression of its mechanism of action through its inhibitory effect upon PEP activity in plasma. S 17092 exhibited central effects, as evidenced by EEG recording in healthy volunteers, and could improve a delayed verbal memory task. Collectively, the preclinical and clinical effects of S 17092 have suggested a promising role for this compound as an agent for the treatment of cognitive disorders associated with cerebral aging.

Further evidence for a dissociation between different forms of mnemonic expressions in a mouse model of age-related cognitive decline: effects of tacrine and S 17092, a novel prolyl endopeptidase inhibitor

It has been demonstrated previously on the radial maze that the emergence of an age-related mnemonic impairment is critically dependent on the form which the discrimination problems took. Hence, when the arms were presented one by one (i.e., successive go-no-go discrimination), both adult and aged mice learned to distinguish between positive (baited) and negative (unbaited) arms readily, as evidenced by their increased readiness to enter positive relative to negative arms (i.e., by a differential in arm-entry latencies). A selective impairment in the aged mice was seen when these arms were presented subsequently as pairs, such that the mice were confronted with an explicit choice (i.e., simultaneous 2-choice discrimination). When discriminative performance was measured by the differential run speed between positive and negative arms, aged mice were also impaired. This was particularly pronounced in the 2-choice discrimination condition. We examined the effects of tacrine (3mg/kg, subcutaneously) or S 17092 (10mg/kg, orally) in aged mice on the three behavioral indices of this 2-stage spatial discrimination paradigm. The results indicated that: (1) Tacrine, but not S 17092, enhanced the acquisition of go-no-go discrimination as reflected in arm-entry latencies; (2) both drugs improved choice accuracy in simultaneous discrimination, although the effect of tacrine was less striking and, in particular, far from statistical significance in the very first 2-choice responses; and (3) neither drugs significantly affected run-speed performance. We conclude further that the specific patterns of drug effects on the three indices of discriminative performance might suggest that each index is associated with a distinct form of mnemonic expression relying on separate neural systems.