Simultaneous impairment of passive avoidance learning and nociception in rats following chronic swim stress.

BACKGROUND: Stress can alter response to nociception. Under certain circumstances stress enhances nociception, a phenomenon which is called stress-induced hyperalgesia (SIH). While nociception has been studied in this paradigm, possible alterations occurring in passive avoidance (PA) learning after exposing rats to this type of stress has not been studied before. MATERIALS AND METHODS: In the current study, we evaluated the effect of chronic swim stress (FS) or sham swim (SS) on nociception in both spinal (tail-flick) and supraspinal (53.5°C hot-pate) levels. Furthermore, PA task was performed to see whether chronic swim stress changes PA learning or not. Mobility of rats and anxiety-like behavior were assessed using open-field test (OFT). RESULTS: Supraspinal pain response was altered by swim stress (hot-plate test). PA learning was impaired by swim stress, rats in SS group did not show such impairments. Rats in the FS group showed increased mobility (rearing, velocity, total distant moved (TDM) and decreased anxiety-like behavior (time spent in center and grooming) compared to SS rats. CONCLUSIONS: This study demonstrated the simultaneous impairment of PA and nociception under chronic swim stress, whether this is simply a co-occurrence or not is of special interest. This finding may implicate a possible role for limbic structures, though this hypothesis should be studied by experimental lesions in different areas of rat brain to assess their possible role in the pathophysiology of SIH.

Gender difference in motor impairments induced by chronic administration of vinblastine.

OBJECTIVES: Neurotoxicity of anticancer drugs complicates treatment of cancer patients. Vinblastine (VBL) is reported to induce motor and cognitive impairments in patients receiving chronic low-dose regimen. MATERIALS AND METHODS: The effects of VBL treatment on motor, learning and memory functions of male and female Wistar rats were studied by behavioral related tests. Animals were given chronic intraperitoneal injections of VBL (0.2 mg/kg/week for 5 weeks) from postnatal day 23 to 52. Motor function was evaluated using grasping test and balancing was evaluated by the rotarod. Spatial learning and memory and anxiety-like behavior were determined using Morris water maze (MWM) task and open field test, respectively. RESULTS: Administration of VBL caused severe damage to motor and balance function of male rats in comparison to female rats treated with VBL and rats treated with saline. Memory and locomotion were affected in both male and female rats compared with saline treated rats, while a sex difference was also observed in these parameters; male rats showed more impairment compared with female ones. Both male and female rats showed cognitive impairments in MWM task and no sex differences were observed in these functions. CONCLUSION: Results revealed that VBL is a potent neurotoxic agent and despite the profound effect of VBL on motor and cognitive functions, it seems that male rats are more susceptible to motor deficits induced by VBL.