The activation of these receptors can be achieved by intraperitoneal injection of a biologically inert synthetic compound, CNO. There has been concern regarding the potential retro-reduction of CNO to clozapine, a well-known atypical antipsychotic drug (Löffler et al., 2012). However, for several reasons, our results cannot be explained

by this back metabolism. First, while CNO retro-reduction to clozapine has been observed in humans and guinea pigs (Jann et al., 1994), back metabolism AZD6738 research buy could not be detected in rats and mice (Guettier et al., 2009; Jann et al., 1994). Second, CNO-treated GFP-expressing control mice did not show any alteration in any of the tested behaviors compared to saline groups. This includes behavior that has been shown to be sensitive to clozapine such as locomotor activity (McOmish et al., 2012). Finally, clozapine has been reported to alter MD firing (Lavin and Grace, 1998). While we found a decrease in MD neuronal firing rate in MDhM4D mice injected with CNO (Figures 2B–2D) we did not see any firing rate changes in mice that do not express the hM4D receptor (Figure 2C, inset). AZD2281 A major limitation of clinical studies is that they cannot draw causal relations between observed anatomical/functional deficits and specific symptoms. Using pharmacogenetic tools in combination with in vivo recordings from awake behaving

animals we found that even a subtle decrease L-NAME HCl in MD activity can lead to altered MD-PFC functional connectivity and prefrontal-dependent cognitive deficits. Based on these findings we propose that abnormalities found in the MD of patients with schizophrenia could participate to the pathogenesis of cognitive deficits. All protocols used in the present study were approved by the Institutional Animal Care and Use Committee (IACUC) at Columbia University. Mice were C57/Bl6 males purchased from Jackson Laboratory and housed under a 12 hr, light-dark cycle in a temperature-controlled environment with food and water available ad libitum. For the behavioral experiments (reversal learning and T maze tasks), mice were food restricted

and maintained at 85% of their initial weight. For this, they were limited to 1 hr 30 daily access to food in the home cage. After testing, mice were sacrificed and the expression as well as the location of GFP expression was verified to ensure that we correctly targeted the MD (Figure S5). Mice for which GFP was not visible or in an incorrect location were removed from the final analysis. Clozapine-N-Oxide (CNO) (Sigma) was dissolved in PBS to a final concentration of 0.2 mg/ml. PBS or CNO (2 mg/kg) was administered intraperitoneal to the mice 30 min before behavioral testing or in vivo recording (based on personal observations and Alexander et al. [2009]). For thalamic slice physiology CNO was diluted into 1 μM with artificial cerebrospinal fluid.