Ketamine alters cortical integration of GABAergic interneurons and induces long-term sex-dependent impairments in transgenic Gad67-GFP mice

Abstract

Ketamine, a non-competitive N-methyl-D-aspartate (NMDA) antagonist, widely used as an anesthetic in neonatal pediatrics, is also an illicit drug named Super K or KitKat consumed by teens and young adults. In the immature brain, despite several studies indicating that NMDA antagonists are neuroprotective against excitotoxic injuries, there is more and more evidence indicating that these molecules exert a deleterious effect by suppressing a trophic function of glutamate. In the present study, we show using Gad67-GFP mice that prenatal exposure to ketamine during a time-window in which GABAergic precursors are migrating results in (i) strong apoptotic death in the ganglionic eminences and along the migratory routes of GABAergic interneurons; (ii) long-term deficits in interneuron density, dendrite numbers and spine morphology; (iii) a sex-dependent deregulation of γ-aminobutyric acid (GABA) levels and GABA transporter expression; (iv) sex-dependent changes in the response to glutamate-induced calcium mobilization; and (v) the long-term sex-dependent behavioral impairment of locomotor activity. In conclusion, using a preclinical approach, the present study shows that ketamine exposure during cortical maturation durably affects the integration of GABAergic interneurons by reducing their survival and differentiation. The resulting molecular, morphological and functional modifications are associated with sex-specific behavioral deficits in adults. In light of the present data, it appears that in humans, ketamine could be deleterious for the development of the brain of preterm neonates and fetuses of addicted pregnant women.

The Zona Incerta Regulates Communication between the Superior Colliculus and the Posteromedial Thalamus: Implications for Thalamic Interactions with the Dorsolateral Striatum

“…To visualize neurons in ZI that contained GABA, coronal sections were processed for glutamic acid decarboxylase (GAD) using procedures adapted from previous reports (Oostland et al, 2011;Aligny et al, 2014). The sections were rinsed in 0.1 M PBS for 20 min before being placed in a PBS-based blocking solution that contained 0.3 M glycine, 5% goat serum, 1% bovine serum albumin, and 0.1% Triton X-100, pH 7.4, at room temperature for 1 h. Sections were then incubated overnight with polyclonal rabbit anti-GAD 65/67 antibody (1:250, ab49832, Abcam) diluted in PBS at 4°C.…”

“…By comparison, POm receives inputs from the trigeminal nuclei and sensorimotor cortex (Veinante et al, 2000;Alloway et al, 2003). Synchronous inputs from these sources increase POm responsiveness (Groh et al, 2014), which could contribute to the slow adaptation observed in POm.…”

“…However, no study has demonstrated that activation of the superior colliculus causes excitation of ZI or inhibition of POm. Furthermore, the influence exerted by the superior colliculus on ZI has been questioned by reports asserting that the superior colliculus projects mainly to the subthalamic nucleus (STN), which lies ventral to the ZI (Coizet et al, 2009;Redgrave et al, 2010a).…”

“…This is clinically significant because it could explain why deep brain stimulation of ZI alleviates some symptoms in Parkinson's disease (PD), as well as essential tremor (Plaha et al, 2008;Sun et al, 2008;Blomstedt et al, 2012;Caire et al, 2013). Therefore, we used anatomical tracing along with neuronal recording and stimulation techniques to determine whether collicular activation of ZI can suppress neuronal activity in POm.…”

“…The superior colliculus does not project directly to POm, but it innervates the zona incerta (ZI), which contains GABAergic neurons that project to POm (Barthó et al, 2002;Mitrofanis, 2005). Consistent with this, focal lesions in ZI enhance POm responsiveness to somesthetic stimulation, presumably by destroying the inhibitory projections from ZI (Trageser and Keller, 2004;Lavallée et al, 2005).…”