Prenatal kynurenine exposure in rats: age-dependent changes in NMDA receptor expression and conditioned fear responding

Rationale: Levels of kynurenic acid (KYNA), an endogenous negative modulator of alpha 7 nicotinic acetylcholine receptors (α7nAChRs) and antagonist at glutamatergic N-methyl-d-aspartate receptors (NMDARs), are elevated in the brain of patients with schizophrenia (SZ). In rats, dietary exposure to KYNA’s immediate precursor kynurenine during the last week of gestation produces neurochemical and cognitive deficits in adulthood that resemble those seen in patients with SZ. Objectives: The present experiments examined whether prenatal kynurenine exposure results in age-dependent changes in the kynurenine pathway (KP), expression of selected receptors, and cognitive function. Methods: Pregnant dams were fed unadulterated mash (progeny = ECON) or mash containing kynurenine (100 mg/day; progeny = EKYN) from embryonic day (ED) 15 to 22. Male offspring were assessed as juveniles, i.e., prior to puberty (postnatal day [PD] 32), or as adults (PD70) for brain KYNA levels, α7nAChR and NMDAR gene expression, and performance on a trace fear conditioning (TFC) task. Results: KYNA levels were comparable between juvenile ECON and EKYN rats, whereas EKYN adults exhibited a ~3-fold increase in brain KYNA relative to ECONs. NR2A expression was persistently reduced (30–40 %) in EKYN rats at both ages. Compared to ECON adults, there was a 50 % reduction in NR1, and a trend toward decreased α7nAChR expression, in adult EKYN rats. Surprisingly, juvenile EKYN rats performed significantly better in the TFC paradigm than controls, whereas adult EKYN animals showed the predicted deficits. Conclusions: Collectively, our results provide evidence that KP changes in the fetal brain alter neuronal development and cause age-dependent effects on neurochemistry and cognitive performance

Transient inactivation of the neonatal ventral hippocampus impairs attentional set-shifting behavior:reversal with an α7 nicotinic agonist

Cognitive deficits represent a core symptom cluster in schizophrenia that are thought to reflect developmental dysregulations within a neural system involving the ventral hippocampus (VH), nucleus accumbens (NAC), and prefrontal cortex (PFC). The present experiments determined the cognitive effects of transiently inactivating VH in rats during a sensitive period of development. Neonatal (postnatal day 7, PD7) and adolescent (PD32) male rats received a single bilateral infusion of saline or tetrodotoxin (TTX) within the VH to transiently inactivate local circuitry and efferent outflow. Rats were tested as adults on an attentional set-shifting task. Performance in this task depends upon the integrity of the PFC and NAC. TTX infusions did not affect the initial acquisition or ability to learn an intra-dimensional shift. However, TTX rats required a greater number of trials than did controls to acquire the first reversal and extra-dimensional shift (ED) stages. These impairments were age and region-specific as rats infused with TTX into the VH at PD32, or into the dorsal hippocampus at PD7, exhibited performance in the task similar to that of controls. Finally, acute systemic administration of the partial α7 nicotinic acetylcholine receptor (nAChR) agonist SSR 180711 (3.0 mg/kg) eliminated the TTX-induced performance deficits. Given that patients with schizophrenia exhibit hippocampal pathophysiology and deficits in the ED stages of set-shifting tasks, our results support the significance of transient hippocampal inactivation as an animal model for studying the cognitive impairments in schizophrenia as well as the pro-cognitive therapeutic potential of α7 nAChR agonists

A Comparison of Complications and Reoperations Between Open Reduction and Internal Fixation Versus Primary Arthrodesis Following Lisfranc Injury.

There is a lack of consensus in the literature regarding optimal treatment methods for Lisfranc injuries, and recent literature has emphasized the need to compare open reduction and internal fixation (ORIF) with primary arthrodesis (PA). The purpose of the current study is to compare reoperation and complication rates between ORIF and PA following Lisfranc injury in a private, outpatient, orthopaedic practice. A retrospective chart review was performed on patients undergoing operative intervention for Lisfranc injury between January 2009 and September 2015. A total of 196 patients met the inclusion criteria (130 ORIF, 66 PA), with a mean follow-up of 61.3 and 81.7 weeks, respectively. The ORIF group had a higher reoperation rate than the PA group, due to hardware removal. When hardware removals were excluded, the reoperation rate was similar. Postsurgical complications were compared between the 2 groups with no significant difference. In conclusion, ORIF and PA had similar complication rates. When hardware removals were excluded, the reoperation rates were similar, although hardware removals were more common in the ORIF group compared with the PA group