title: Layer- and area-specificity of the adrenergic modulation of synaptic transmission in the rat neocortex.
abstract: The mammalian neocortex is a multilayered structure receiving extensive adrenergic projections both in rostral and caudal areas. The cellular mechanisms of norepinephrine (NE) in the neocortex are incompletely understood. We used electrophysiology to determine whether NE modulation of synaptic transmission were similar in rostral versus caudal cortical areas, and in infra- versus supra-granular cortical layers. To address these questions we used bath applications of NE (20 µM) to determine its effects on pharmacologically isolated electrically-evoked 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl) propionic acid receptor (AMPAR)-mediated excitatory synaptic currents (eEPSCs), or γ-amino butyric acid A receptor (GABAAR)-mediated inhibitory synaptic currents (eIPSCs). We monitored synaptic currents in pyramidal neurons using whole-cell patch-clamp recordings from supragranular layer 2/3 (L2/3) and infragranular layer 5 (L5) neurons in a thin-slice preparation of rat medial prefrontal cortex (mPFC). These results were compared with the effects in the temporal cortex (TC) under similar experimental conditions. We found that NE uniformly and transiently depressed eEPSCs from supragranular to infragranular layers in both the PFC and the TC. On the contrary, the effects of NE on eIPSC were area- and layer-dependent, as NE enhanced the mean amplitude in TC L2/3 and PFC L5 eIPSCs (which displayed the largest saturation currents in the areas studied) but depressed PFC L2/3 eIPSCs, without affecting TC L5 eIPSCs. While the precise physiological meaning of these results is still unclear, our data are consistent with the existence of a dense noradrenergic-controlled GABAergic cortical network in the PFC, in which L5 may act as a decisional bottleneck for behavioral inhibition.
authors.affiliation: School of Behavioral and Brain Sciences, University of Texas at Dallas, 800 West Campbell Rd., Richardson, TX, 75080-3021, USA.
authors.forename: Swagata
authors.initials: S
authors.lastname: Roychowdhury
authors.forename: Amy N
authors.initials: AN
authors.lastname: Zwierzchowski
authors.forename: Francisco
authors.initials: F
authors.lastname: Garcia-Oscos
authors.forename: Roberto Cuevas
authors.initials: RC
authors.lastname: Olguin
authors.forename: Roberto Salgado
authors.initials: RS
authors.lastname: Delgado
authors.forename: Marco
authors.initials: M
authors.lastname: Atzori
mesh_terms: D000818:Animals; D019579:Neocortex / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011941:Receptors, Adrenergic / Q000502:physiology*; D009435:Synaptic Transmission
chemical_list: D011941:Receptors, Adrenergic