Tonic inhibition of single nucleus accumbens neurons in the rat: a predominant but not exclusive firing pattern induced by cocaine self-administration sessions

A critical transition in cocaine self-administration: behavioral and neurobiological implications

“…Over the past 15 years, several researchers have suggested that the ideal level of cocaine reward may correspond to a specific level of dopamine signaling in the nucleus accumbens that is considerably higher than those evoked during the consumption of natural rewards (Pettit and Justice 1989;Wise et al 1995;Ranaldi et al 1999;Parsons et al 1995). There are some neurophysiological evidence showing that this selfsustained excessive level of dopamine signaling would filter out cortical excitatory inputs to the nucleus accumbens, thereby silencing most, though not all, accumbal output neurons (Peoples et al 1998). A great challenge for future neurobiological research will be to elucidate the specific functional repercussions of this neural silencing effect.…”

Accumbal Neurons that are Activated during Cocaine Self-Administration are Spared from Inhibitory Effects of Repeated Cocaine Self-Administration

“…Previous studies documented that accumbal neurons exhibit multiple types of firing patterns during the self-administration session (Carelli et al, 1993;Chang et al, 1994;Peoples and West, 1996;Peoples et al, 1998bPeoples et al, , 2004Uzwiak et al, 1997). These firing patterns include the following: (1) changes in firing time-locked to events that occur at the onset of the self-administration session; (2) changes in firing time-locked to the cocaine-reinforced lever press; and (3) changes in average, tonic, firing that occur during the selfadministration session relative to the pre-and postsession baseline periods.…”

“…These firing patterns include the following: (1) changes in firing time-locked to events that occur at the onset of the self-administration session; (2) changes in firing time-locked to the cocaine-reinforced lever press; and (3) changes in average, tonic, firing that occur during the selfadministration session relative to the pre-and postsession baseline periods. These firing patterns were identified in the present study according to previously established statistical criteria (Peoples and West, 1996;Uzwiak et al, 1997;Peoples et al, 1998bPeoples et al, , 2004, which are described below. As a frame of reference for comparisons to investigations that use percent change criteria (eg Hollander and Carelli, 2005;Chang et al, 1994), the statistical criteria used to test for task-related firing responses were moderately more stringent than a percent-change rule of 100%.…”

“…This hypothesis is based on a number of previous observations. Numerous studies have shown that during cocaine selfadministration sessions, only a subset of accumbal neurons show changes in activity related to encoding aspects of the instrumental task (eg Carelli et al, 1993;Peoples et al, 1997Peoples et al, , 1998b. The majority of those neurons show either transient or tonic increases in firing during the period of drug exposure (referred to as Task-Activated neurons).…”

Connaissances précliniques actuelles sur la neurobiologie de la cocaïne

“…Ceci semble se faire essentiellement grâce à la présence de récepteurs D 2 présynaptiques sur la terminaison glutamatergique qui seraient capables d'inhiber la libération de glutamate [12]. Lors de l'administration chronique de cocaïne, ce filtrage dopaminergique pourrait être fortement augmenté, de part la plasticité synaptique engendrée par l'exposition à la drogue et la libération de dopamine, ce qui aura alors pour conséquence d'entraîner une suppression de l'activité neuronale dans le noyau accumbens (qui est GABAergique) [13], et donc une désinhibition de l'hypothalamus latérale. Cette levée d'inhibition pourrait en grande partie être responsable des effets récompensants de la cocaïne (revue dans [14]).…”