We have previously shown that in L6-GLUT4myc rat skeletal muscle cells, acute treatment with leptin reduced insulin-stimulated glucose uptake without altering insulin-stimulated GLUT4 translocation. In contrast, we show here that the ability of leptin to increase phosphorylation of its receptor and to reduce insulin-stimulated glucose uptake was lost in cells that were continuously exposed to leptin for 24 h. This desensitization correlated with an increase in expression of suppressor of cytokine signaling-3 (SOCS-3). Time course analysis demonstrated that the transition from acute to chronic effects of leptin occurs after 2 h. The desensitization of leptin action at 24 h was not reversed by 30 min washout period prior to re-exposing cells to leptin. However, despite insulin-stimulated glucose uptake being unaffected upon 24 h preincubation with leptin, a small but significant decrease (37%) in insulin-stimulated GLUT4 translocation and phosphorylation of Akt on T308 was detected. Insulin-stimulated phosphorylation of Akt on S473 or of p38 MAPK were unaffected. These results suggest that the chronic leptin treatment leads to desensitization of leptin signaling yet can simultaneously decrease the ability of insulin to phosphorylate Akt on T308 and translocate GLUT4. However, this does not manifest as a reduction in total glucose uptake into L6 myotubes.

Sulphamethoxazole-HSR but not AC-HSR patients may present a cross-reactivity to ZNS-HSR. The use of LTA to predict a possible ZNS reaction is recommended for SMX-sensitive individuals who prescribed ZNS.

Tardive dyskinesia (TD) is a late-onset side effect mainly affecting the orofacial region of patients treated chronically with classic antipsychotic drugs such as haloperidol (HAL). The causes of TD remain unknown. We hypothesized that faulty synaptic re-organization might be related to TD-like syndromes and used the vacuous chewing movements (VCM) model in rats to investigate the expression of four synaptic proteins, synaptophysin, syntaxin, spinophilin and PSD-95, in brains of HAL-treated rats. Male Sprague-Dawley rats were treated for 14 weeks with either haloperidol decanoate (21 mg/kg once every 3 weeks, I.M) or vehicle and VCMs were monitored on a weekly basis. As expected, VCMs developed reliably and were consistently more pronounced in some rats than in others. Using immunohistochemistry in anatomically preserved brain sections as well as Western Blot analyses of whole cells or synaptosomal fractions in striatal tissue, we found no significant effect of chronic HAL on levels of these proteins. Neither did we find significant differences in the levels of the four synaptic markers when comparing rats showing High vs. Low levels of VCMs. These results suggest that structural synaptic alterations (e.g. involving increased number of synapses) may not be the underlying mechanism of oral dyskinesias induced by chronic antipsychotic drug treatment. The possibility that functional neuroplastic changes occur remains to be investigated.