Post‐training cocaine exposure facilitates spatial memory consolidation in C57BL/6 mice

Abstract

In the present study, we examined the ability of post-training injections of cocaine to facilitate spatial memory performance using the Morris water maze (MWM). We also investigated the role that hippocampal protein kinase A (PKA) and extracellular signal-regulated kinase 1/2 (ERK) signaling may play in cocaine-mediated spatial memory consolidation processes. Male and female C57BL/6 mice were first trained in a MWM task (eight consecutive trials) then injected with cocaine (0, 1.25, 2.5, 5, or 20 mg/kg), and memory for the platform location was retested after a 24 hr delay. Cocaine had a dose-dependent effect on spatial memory performance because only the mice receiving 2.5 mg/kg cocaine displayed a significant reduction in latency to locate the platform. No sex differences in MWM performance were observed; however, females showed higher hippocampal levels of PKA when compared to males. A second experiment demonstrated that 2.5 mg/kg cocaine enhanced MWM performance only when administered within 2, but not 4 hr after spatial training. We also found that cocaine (2.5 mg/kg) increased ERK2 phosphorylation within the hippocampus and one of its downstream targets (ribosomal S6 kinase), a mechanism that may be responsible, at least in part, for the enhanced cocaine-mediated spatial memory performance. Overall, these data demonstrate that a low dose of cocaine (2.5 mg/kg) administered within 2-hr after training facilitates MWM spatial memory performance in C57BL/6 mice.

Social defeat stress induces depression-like behavior and alters spine morphology in the hippocampus of adolescent male C57BL/6 mice

“…Gels were transferred to nitrocellulose membranes in the IBlot ® Dry Blotting System (Life Technologies; Carlsbad, CA) for 9 min. Nitrocellulose membranes were then incubated in blocking solution containing 5% sucrose in Tris Buffered Saline with Tween-20 (TBST; 0.1% Tween-20 in TBS) for 30 min at room temperature (Iñiguez et al., 2012). Samples were incubated with the following primary antibodies overnight: GluA2 (monoclonal; anti-mouse 1:2000; Chemicon, Temecula, CA), D1 (polyclonal; anti-rabbit 1:1000, AbCam, Cambridge, MA), DAT (polyclonal; anti-rabbit 1:1000, Santa Cruz Biotechnology; Santa Cruz, CA), TH (polyclonal; anti-rabbit 1:2000; EMD Millipore, Billerica, MA), PKMζ/PKCζ (polyclonal; anti-rabbit 1:2000; Santa Cruz Biotechnology, Santa Cruz, CA), and GAPDH: (1:2000, Chemicon, Temecula, CA).…”

Altered Gene Expression and Spine Density in Nucleus Accumbens of Adolescent and Adult Male Mice Exposed to Emotional and Physical Stress

“…Each punch contained tissue from both core and shell. Samples (20 μg; estimated through Bradford assay) were treated with β-mercaptoethanol and subsequently electrophoresed on precast 4%–20% gradient gels (Biorad, Hercules, California), as previously described [47]. Proteins were transferred to a polyvinylidene fluoride membrane, washed in 1X Tris-buffered saline with 0.1% Tween-20 (TBST), and blocked in milk dissolved in TBST (5% weight/volume) for one h at 25°C.…”

Effects of psychotropic drugs on second messenger signaling and preference for nicotine in juvenile male mice

“…Ten micro-grams of protein from each sample was treated with β-mercaptoethanol and subsequently electrophoresed on precast 4–20 % gradient gels (Bio-Rad), as previously described (Iñiguez et al 2012; Warren et al 2011). All antibodies were obtained from Cell Signaling (Beverly, Massachusetts).…”