2007), == Electrophysiological Recordings == Interneurons in layers 23 were visualized using infrared differential interference contrast videomicroscopy and distinguished from pyramidal cells based on their small, round, or oval soma and the absence of an apical dendrite. types experienced short spike period, which is not standard for rodent adapting cells. Neurogliaform cells (NGFCs), which coexpressed calbindin and neuropeptide Y, formed the third class, characterized by strong initial adaptation. They did not exhibit the delayed spikes seen in rodent NGFCs. These results indicate that primate interneurons have some specific properties; consequently, direct translation of classification techniques developed from studies in rodents to primates might be improper. Keywords:cerebral cortex, fast-spiking cells, GABA cells, inhibition, parvalbumin, patch clamp == Intro == Cortical -aminobutyric acid (GABA) interneurons are heterogeneous, with subpopulations distinguished by particular mixtures of morphological, physiological, and molecular attributes (Cauli et al. 1997;Kawaguchi and Kubota 1997;McBain and Fisahn 2001) and with variance in these characteristics within subpopulations (Soltesz 2006). In addition, abnormalities of specific types of cortical interneurons are thought to be critical components of the pathophysiological mechanisms underlying human brain disorders such as epilepsy and schizophrenia (DeFelipe 1999;Lewis et al. 2005). However, relatively few studies characterizing the properties of cortical GABA neurons have been performed in monkeys or humans (e.g.,Krimer et al. 2005;Szabadics et al. 2006); for review of earlier studies, seeAvoli and Williamson (1996). As a result, the proper translation of the considerable and growing database of rodent cortical interneurons to an understanding of these human being disorders requires CCNU the ability to determine related types of interneurons across varieties. Although homologous types of interneurons have been reported in multiple varieties, variations have been observed actually between phylogenetically close varieties. For instance, in rat cortex parvalbumin PYR-41 (PV), somatostatin (SST), and calretinin (CR) interneurons constitute primarily nonoverlapping subpopulations (Gonchar and Burkhalter 1997;Kawaguchi and Kubota 1997), whereas in the mouse cortex, a large subpopulation of interneurons coexpresses CR and SST (Xu et al. 2006). Furthermore, compared with rodent neocortex, in the primate neocortex 1) the percentage of cortical neurons that are GABAergic is definitely larger (Gabbott and Bacon 1996;Gabbott et al. 1997), 2) interneurons characterized by a vertical bundling of axons are much more common (Yanez et al. 2005), 3) the developmental source of at least some interneurons appears to differ (Letinic et al. 2002;Molyneaux et al. 2007), and 4) the relative proportions of chemically recognized subtypes of interneurons are dissimilar (Conde et al. 1994;Kawaguchi and Kubota 1997). Moreover, interneurons with firing properties unusual for rodents have been found in monkey prefrontal cortex (Krimer et al. 2005;Povysheva et al. 2007). Therefore, a strong and reliable classification of different interneuron types in the primate neocortex is definitely critically needed. Recently, we attempted to functionally categorize interneurons in monkey dorsolateral prefrontal cortex (DLPFC) by correlating their electrophysiological properties either with morphological types (Krimer et al. 2005) or with calcium-binding protein (CaBP) content (Zaitsev et al. 2005). By using cluster analysis, we shown that monkey interneurons form unique physiological groupings. However, the physiological-based clusters acquired in these studies appeared to contain heterogeneous morphological and molecular types, and thus a different approach for classification is needed. In order to address this problem, in this study we used morphological criteria like a starting point for identifying subsets of interneurons in monkey DLPFC. Of the 8 morphological types of coating 23 interneurons recognized, the electrophysiological and molecular PYR-41 properties of 4 types have not been previously explained in primates. We found that monkey interneurons of the same morphological type exhibited related electrophysiological and molecular characteristics; at least some morphological types of monkey interneurons shown different membrane properties from those for homologous morphological types explained in rat. We did not observe interneurons, exhibiting late-spiking, stuttering, or bursting firing patterns, which are typical for some types of rodent interneurons, while we recognized some firing patterns that are unusual for rats. These findings show that direct translation of classification techniques developed from studies in rodents to primates might be improper. == Materials and Methods == == Slice Preparation == Seventeen experimentally naive young adult (3.56 kg, 3.54 years old) male long-tailed macaque monkeys (Macaca fascicularis) were used in this study. Animals were treated according to the recommendations layed out in the National Institutes of Health Guideline for the Care and Use of Laboratory Animals, as authorized by the University or college of Pittsburgh Institutional Animal Care and Use Committee. PYR-41 The procedure used to obtain cells from your DLPFC has been previously described in detail (Gonzalez-Burgos et al. 2004). Briefly, animals were treated with ketamine hydrochloride (25 mg/kg, intramuscular [im]), dexamethasone phosphate (0.5 mg/kg, im), and atropine.