NMDA receptors subserve persistent neuronal firing during working memory in dorsolateral prefrontal cortex.

Neurons in the primate dorsolateral prefrontal cortex (dlPFC) generate persistent firing in the absence of sensory stimulation, the foundation of mental representation. Persistent firing arises from recurrent excitation within a network of pyramidal Delay cells. Here, we examined glutamate receptor influences underlying persistent firing in primate dlPFC during a spatial working memory task. Computational models predicted dependence on NMDA receptor (NMDAR) NR2B stimulation, and Delay cell persistent firing was abolished by local NR2B NMDAR blockade or by systemic ketamine administration. AMPA receptors (AMPARs) contributed background depolarization to sustain network firing. In contrast, many Response cells were sensitive to AMPAR blockade and increased firing after systemic ketamine, indicating that models of ketamine actions should be refined to reflect neuronal heterogeneity. The reliance of Delay cells on NMDAR may explain why insults to NMDARs in schizophrenia or Alzheimer's disease profoundly impair cognition.

Comprehensive dental treatment under general anesthesia in healthy and disabled children.

BACKGROUND: Differences in dental treatment under general anesthesia (GA) in healthy and disabled children are rarely reported. This retrospective study evaluated the characteristics and treatment modalities performed under general anesthesia in pediatric dental patients at Taipei Chang Gung Memorial Hospital between 2004 and 2005, and compared the different treatment patterns performed in healthy children and children with special health care needs. METHODS: The data were reviewed in pediatric patients from 1 to 18 years old who underwent dental treatment performed under general anesthesia from January 2004 to December 2005. Patients with special health care needs who had at least one type of mental or physical disability were assigned to the disabled group (Group D) and the other healthy patients were assigned to the healthy group (Group H). The treatment modalities of operative restoration, crowns, pulp therapy, sealant and extracted teeth were compared in the two groups. RESULTS: A total of 185 patients were assigned to group H and 112 to group D. The patients in group D were significantly older than those in group H. There were no significant differences in the mean number of teeth treated between the two groups. However, there was a significantly greater mean total number of teeth extracted in group D patients (p < 0.001). In addition, there were more stainless steel crown reconstructions (p < 0.05) and pulp therapies (p < 0.001) performed in group H patients. In group D, there were no significant differences in the total number of teeth extracted between the 1-3 year old patients and the 3-6 year-old patients (p = 0.99). CONCLUSIONS: For very young children or those with special health care needs, dental treatment performed under general anesthesia is beneficial and efficient. The findings of this study suggest that underlying medical or mental conditions may influence the dental condition and treatment modality provided.

Effects of immobilization stress on neurochemical markers in the motivational system of the male rat.

Mesolimbic regions involved in motivated behavior are altered in animals undergoing repeated exposure to social stress. Here we test the hypothesis that other forms of persistent stress would also influence these same endpoints. Adult male Sprague-Dawley rats were exposed to immobilization stress either once (2 h) or repeatedly (2 hx10 days) and brains were harvested immediately after the last immobilization. A trio of indirect markers associated with dopaminergic activity was measured including dopamine transporter (DAT) and dopamine D2 receptor subtype (D2r) ligand levels as well as mRNA levels of the endogenous opioid enkephalin (ENK-mRNA). A single 2-h session of immobilization stress produced an increase in striatal ENK-mRNA levels and DAT ligand binding compared with group-housed controls. In animals undergoing repeated immobilization stress and singly housed post-stress, we found a significant reversal in the direction of ENK-mRNA levels and DAT binding in the striatum, in addition to an increase in D2r-binding density in the shell of the nucleus accumbens compared with single-stress-exposed rats. In another experiment using the same stress paradigm but allowing pair-housing post-stress, we found no alteration of ENK-mRNA but significant increases in DAT and D2r binding in the dorsal striatum. A major difference between single and group housing is the habituation of the corticosterone (CORT) stress response over 10-day stress in group-housed rats. The present results parallel previous findings by our laboratory that repeated stress results in a relative reduction of ENK-mRNA levels and increased D2r-binding density in the striatum of rats. Furthermore, our data are consistent with the hypothesis that chronic stress induces an allostatic attenuation of the mesolimbic dopaminergic system in animals that do not habituate to the stressor, possibly due in part to persistent CORT elevations.