Opiate addiction is characterized by progressive increases in drug intake over time suggesting maladaptive changes in motivational and reward systems. These behaviors are mediated by dopaminergic neurons originating from the ventral tegmental area (VTA), and long-term changes of these dopaminergic neurons are attributed to increased postsynaptic glutamatergic activation. Indeed, chronic morphin...

The vagotonic effect of chronic morphine on the parasympathetic control of the heart was examined in dogs treated with morphine for 2 wk. Because normal vagal function is critical to myocardial stability, the study was conducted to evaluate for potential impairments following chronic vagal stimulation. The hypothesis that persistent vagal outflow would result in a loss of vagal reserve and redu...

The present study was performed to determine the effect of intracerebroventricular (ICV) administration of W-7, a specific calmodulin inhibitor, on the development of tolerance to antinociceptive effect morphine administration. This study was carried out on male wistar rats, weighing 200-250 g. Morphine was administered daily (15 mg/kg for 8 days). The threshold to thermal nociceptive stimuli w...

Six female adult Macaca mulatta monkeys were made dependent upon morphine sulfate and wermanted with a chronic indwelling needle in the lateral ventricle of the brain for sterile intraventricular injections. Both B-endorphin and morphine, in a dose dependent manner given intraventricularly suppressed the signs of 14 hour acute morphine abstinence. On a molar basis, 8-endorphin was more active t...

there are several conflicting evidences showing the effect of morphine on learning and memory processes. in the present study the effect of chronic morphine administration on passive avoidance, active avoidance and spatial learning and memory of morphine dependent male rats using passive avoidance shuttle box and morris water maze tasks were investigated, respectively. male rats received morphi...

Objective(s):Neuropathic pain is caused by lesions or diseases affecting the somatosensory system and often responds poorly to typical medications.  In this study, we evaluated anti-nociceptive effects of morphine, gabapentin and their combination on heat hyperalgesia, cold and mechanical allodynia in chronic constriction injury (CCI) model of neuropathic pain in rats. Materials and Methods: Mo...

GABAergic drugs can change analgesic effect of morphine. Wide dynamic range (WDR) neurons play an important role in pain transmission and may change behaviors in morphine tolerance. In this study WDR neuron behaviors in morphine tolerant rats and rats treated with GABA agonists, were recorded to elucidate the effect of morphine and GABA agonists on WDR behavioral changes. Rats were divided to 4...

GABAergic drugs can change analgesic effect of morphine. Wide dynamic range (WDR) neurons play an important role in pain transmission and may change behaviors in morphine tolerance. In this study WDR neuron behaviors in morphine tolerant rats and rats treated with GABA agonists, were recorded to elucidate the effect of morphine and GABA agonists on WDR behavioral changes. Rats were divided to 4...

Chronic administration of morphine results in the development of tolerance to the analgesic effects and to inhibition of upper gastrointestinal motility but not to colonic motility, resulting in persistent constipation. In this study we examined the effect of chronic morphine in myenteric neurons from the adult mouse colon. Similar to the ileum, distinct neuronal populations exhibiting afterhyp...

Opiates disrupt neural functions in many brain areas, including visual cortex. Previous studies have indicated substantial changes of many neuronal response properties induced by chronic morphine exposure in the visual information processing system. However, it remains unclear whether neuronal contrast coding is also affected. To investigate this issue, we measured the contrast response functio...