Human and preclinical models of addiction demonstrate that gonadal hormones modulate acquisition of drug seeking. Little is known, however, about the effects of these hormones on extinction of drug-seeking behavior. Here, we investigated how 17ß-estradiol (E[subscript 2]) affects expression and extinction of cocaine seeking in female rats. Using a…

Two-way active avoidance (2WAA) involves learning Pavlovian (association of a sound cue with a foot shock) and instrumental (shock avoidance) contingencies. To identify regions where dopamine (DA) is involved in mediating 2WAA, we restored DA signaling in specific brain areas of dopamine-deficient (DD) mice by local reactivation of conditionally…

Mice communicate through visual, vocal, and olfactory cues that influence innate, nonassociative behavior. We here report that exposure to a recently fear-conditioned familiar mouse impairs acquisition of conditioned fear and facilitates fear extinction, effects mimicked by both an olfactory chemosignal emitted by a recently fear-conditioned…

It is known from studies outside the brain that upon binding to its receptor, angiotensin-(1-7) elicits the release of prostanoids and nitric oxide (NO). Cyclooxygenase (COX) is a key enzyme that converts arachidonic acid to prostaglandins. Since there are no data available so far on the role of COX-2 in the amygdala, in a first step we…

Previous reports have shown that overexpression of the growth- and plasticity-associated protein GAP-43 improves memory. However, the relation between the levels of this protein to memory enhancement remains unknown. Here, we studied this issue in transgenic mice (G-Phos) overexpressing native, chick GAP-43. These G-Phos mice could be divided at…

Studies of gene expression following fear conditioning have demonstrated that the inducible transcription factor, "egr-1," is increased in the lateral nucleus of the amygdala shortly following fear conditioning. These studies suggest that "egr-1" and its protein product Egr-1 in the amygdala are important for learning and memory of fear. To…

Stress facilitates memory formation, but only when the stressor is closely linked to the learning context. These effects are, at least in part, mediated by corticosteroid hormones. Here we demonstrate that corticosterone rapidly facilitates synaptic potentiation in the mouse hippocampal CA1 area when high levels of the hormone and high-frequency…

Cocaine produces multiple neuroadaptations with chronic repeated use. Many of these neuroadaptations can be reversed or normalized by extinction training during withdrawal from chronic cocaine self-administration in rats. This article reviews our past and present studies on extinction-induced modulation of the neuroadaptive response to chronic…

Metabotropic glutamate receptors (mGluRs) are known to play a role in synaptic plasticity and learning. We have previously shown that mGluR7 deletion in mice produces a selective working memory (WM) impairment, while other types of memory such as reference memory remain unaffected. Since WM has been associated with Theta activity (6-12 Hz) in…

We investigated whether postextinction administration of methylene blue (MB) could enhance retention of an extinguished conditioned response. MB is a redox compound that at low doses elevates cytochrome oxidase activity, thereby improving brain energy production. Saline or MB (4 mg/kg intraperitoneally) were administered to rats for 5 d following…