Basic and Clinical Neuroscience
Volume:1 Issue: 1, Autumn 2009

Parkinson's disease (PD) is a neuropathological disorder involving the degeneration of dopaminergic neurons in the substantia nigra, with the subsequent loss of their terminals in the striatum. Quercetin, a natural flavonoid, is a strong antioxidant and radical scavenger. Therefore, its neuroprotective effect in a model of Parkinson’s disease in rat was evaluated. For this purpose, unilateral intrastriatal 6-hydroxydopamine (6-OHDA)-lesioned rats were pretreated with quercetin (20 mg/kg; i.p.) 1 hour before surgery and treated once a day for one month. Nissl-stained neurons of substantia nigra pars compacta (SNC) were counted. Number of Nissl-stained neurons in left side of SNC of lesion group was lower relative to sham-operated group (p<0.005) and it was higher in quercetin-treated lesion group as compared to untreated lesion group (p<0.01). Flavonoid quercetin administration for one month could protect the neurons of SNC against 6-OHDA toxicity.

Neurodegeneration change is one of the hallmark symptoms of which Alzheimer’s disease (AD) can be modeled by β-amyloid injection into specific regions of brain. (-)-Epigallocatechin-3-gallate (EGCG) is a potent antioxidant agent that its role against oxidative stress and inflammation has been shown in prior studies. In the present study, we have wanted to determine whether EGCG administration protects against β-amyloid induced cell damages in rats. Animals (male Wistar rats) divided into four groups: sham operated (SH), EGCG-pretreated sham operated (SH + EGCG), untreated lesion (L), and EGCG-pretreated lesion (L + EGCG). Animals in L, L + EGCG, and SH + EGCG groups received sterile saline or saline plus EGCG (10 mg/kg) intraperitoneally one day pre-surgery and every other day for three weeks. The lesion was induced one day after EGCG treatment by injection of water or water containing 2 nmol/µl of β-amyloid (1-40) into the hippocampal fissure. We evaluat ed the morphological changes of hippocampus specially CA3 region by nissl staining after three weeks of surgery. We found that β-amyloid (1-40) injection into hippocampus causes cell death of CA3 region in L group in comparison with SH group which also occurs in the Alzheimer’s disease. On the other hand, treatment with EGCG can improve the validity of these cells in hippocampus. We concluded that EGCG could be effective in protection against pathogenesis of Alzheimer’s disease.

Diabetic rats display exaggerated hyperalgesic behavior in response to noxious stimuli that may resemble and model aspects of painful diabetic neuropathy in humans. This study was designed to investigate the effect of Nigella sativum (NS) on formalin-induced nociceptive responses (standard formalin test) in streptozotocin (STZ)-induced diabetic rats. For this purpose, STZ-diabetic rats received Nigella sativum mixed with standard rat chow at a weight ratio of 6.25% orally for a period of one month. It was found out that NS treatment did cause a significant reduction in blood glucose in diabetic rats and NS-treated diabetic rats exhibited a lower nociceptive score as compared to untreated-diabetic ones. Meanwhile, NS treatment reduced the nociceptive score in both phases of the formalin test. In contrast, sodium salicylate as positive control only reduced this score in the second phase of the test. The results suggest therapeutic potential of NS feeding for treating painful diabetic neuropathy.

Intracerebroventricular (ICV) injection of streptozotocin (STZ) causes cognitive impairment in rats. The beneficial effect of genistein (GEN) was investigated on ICV STZ-induced learning, memory, and cognitive impairment in male rats. For this purpose, rats were injected with ICV STZ bilaterally, on days 1 and 3 (3 mg/kg). The STZ-injected rats received GEN (1 mg/kg/day, p.o.) starting one day pre-surgery for two weeks. The learning and memory performance was assessed using passive avoidance paradigm, and for spatial cognition evaluation, radial eight-arm maze (RAM) task was used. It was found out that GEN-treated STZ-injected rats show higher correct choices and lower errors in RAM than vehicle-treated STZ-injected rats. In addition, GEN administration significantly attenuated learning and memory impairment in treated STZ-injected group in passive avoidance test. These results demonstrate the effectiveness of GEN in preventing the cognitive deficits caused by ICV STZ in rats and its potential in the treatment of neurodegenerative diseases such as Alzheimer's disease (AD).

Diabetic rats display exaggerated hyperalgesic behavior in response to noxious stimuli that may resemble and model aspects of painful diabetic neuropathy in humans. This study was designed to investigate the effect of Trigonella foenum-graecum (TFG) on formalin-induced nociceptive responses (standard formalin test) in streptozotocin (STZ)-induced diabetic rats. For this purpose, STZ-diabetic rats received intraperitoneal injection of aqueous leaf extract of TFG (200 mg/kg every other day for a period of one month). It was found out that TFG treatment did cause a significant reduction in blood glucose in diabetic rats and TFG-treated diabetic rats exhibited a lower nociceptive score as compared to untreated-diabetic ones. Meanwhile, TFG treatment reduced the nociceptive score in both phases of the formalin test. In contrast, sodium salicylate as positive control only reduced this score in the second phase of the test. The results suggest therapeutic potential of aqueous extract of fenugreek for treating painful diabetic neuropathy.

Diabetes mellitus accompanies with disturbances in learning, memory, and cognitive skills in the human society and experimental animals. Considering the beneficial antidiabetic potential of Apium graveolens (AG), this research study was conducted to evaluate the effect of chronic i.p. administration of AG on learning and memory in diabetic rats using passive avoidance and Y-maze tests. Female Wistar rats were randomly divided into control, AG-treated control, diabetic, and AG-treated diabetic groups. AG treatment continued for 4 weeks. For induction of diabetes, streptozotocin was injected i.p. at a single dose of 60 mg/kg. For evaluation of learning and memory, initial latency (IL) and step-through latency (STL) were determined at the end of study using passive avoidance test. Meanwhile, alternation behavior percentage was determined using Y maze. There was a significant increase (p<0.05) in IL in diabetic and AG-treated diabetic groups after 4 weeks as compared to control group. In this respect, there was no significant difference between diabetic and AG-treated diabetic groups. On the other hand, STL significantly decreased (p<0.05) in diabetic group and significantly increased (p<0.05) in AG-treated diabetic group as compared to control group at the end of study. In addition, STL did not significantly change in AG-treated control group in comparison with control group. In addition, results of Y-maze test showed that there is no significant difference between diabetic and Ag-treated diabetic groups and between control and Ag-treated control group regarding alternation behavior. In summary, chronic oral administration of AG could enhance the consolidation and recall capability of stored information only in diabetic animals and did not affect spatial memory of diabetic animals.

Hyperalgesia is considered as one the marked signs of subchronic diabetes mellitus that could affect the life style of the patients. With c onsidering the potential anti-diabetic effect of the medicinal plant Withania somnifera (WS)(ashwagandha), this study was designed to investigate the analgesic effect of WS on formalin-induced nociceptive responses (standard formalin test) in diabetic rats. Rats were divided into control, WS-treated control, diabetic, sodium salicylate (SS)-treated control and diabetic and WS-treated diabetic groups. For induction of diabetes, streptozotocin (STZ) was used at a single dose. The treatment groups received oral administration of ashwagandha -mixed rat pellet (6.25%) for two months. The results showed that diabetic rats exhibited a higher score of pain at both phases of the formalin test and WS-treated diabetic rats exhibited a lower nociceptive score at both phases of the test (p<0.05). Meanwhile, SS administration significantly reduced pain score only at chronic phase of the test in the diabetic group (p<0.01). Taken together, these results indicate that two-month administration of ashwagandha could attenuate nociceptive score in an experimental model of diabetes mellitus and this may be considered as a potential treatment for painful diabetic neuropathy.

Diabetes mellitus accompanies with disturbances in learning, memory, and cognitive skills in the human society and experimental animals. Considering the beneficial antidiabetic potential of Nigella sativum (NS), this research study was conducted to evaluate the effect of chronic consumption of NS on learning and memory in diabetic rats using passive avoidance and Y-maze tests. Male Wistar rats were randomly divided into control, NS-treated control, diabetic, and NS-treated diabetic groups. NS treatment continued for 1 month. For induction of diabetes, streptozotocin was injected i.p. at a single dose of 60 mg/kg. For evaluation of learning and memory, initial latency (IL) and step-through latency (STL) were determined at the end of study using passive avoidance test. Meanwhile, alternation behavior percentage was determined using Y maze. There was a significant increase (p<0.05) in IL in diabetic and NS-treated diabetic groups after 4 weeks as compared to control group. In this respect, there was no significant difference between diabetic and NS-treated diabetic groups. On the other hand, STL significantly decreased (p<0.05) in diabetic group and significantly increased (p<0.01) in NS-treated diabetic group as compared to control group at the end of study. In addition, results of Y-maze test showed that there is a significant difference between diabetic and NS-treated diabetic groups (p<0.05) regarding alternation behavior. In summary, chronic oral administration of NS could enhance the consolidation and recall capability of stored information and spatial memory in diabetic animals. Keywords: