ABSTRACT
Objective To investigate the effects of dorsal hippocampal lesions (DH) or fimbria-fornix transection (FF) on the learning and memory of conditioned fear and the heart rate and blood pressure in rats.Methods Nineteen male adult Wistar rats were used in this experiment.They were implanted telemetry sensors in their abdominal aortas.Two week later,six of the rats were subjected to permanent NMDA-induced neurotoxic lesions to the dorsal hippocampus (DH) and seven for the fimbria-fornix transection (FF)through stereotactic brain surgery,the left six were treated with saline as the control (Sham).All rats were subjected to a conditioned fear experiment.Meanwhile,changes in heart rate and blood pressure were measured.Results There was no significant difference in heart rate and blood pressure among the rats with the hippocampal operation or fimbria-fornix transection.In the acquisition of conditioned fear,there were significant difference in freezing time among the three group in both inter-trial-interval (ITI) and conditioned stimulus (CS) process (all P＜0.05).The freezing time of the FF group showed significantly lower than that of the Sham group (P＜0.05).There was no significant difference in heart rate and blood pressure among the three group(P＞0.05).In the test of conditioned contextual fear memory,the freezing time percentage in the FF group ((0.31±0.16) ％) significantly lower than that in the Sham group ((2.78± 1.23) ％) (P＜0.05)at the first 3 min of the test.There was a significant difference in heart rate among the three group.The heart rate of FF group ((436.42± 10.16) times/min) was significantly lower than that of the Sham group ((472.48±4.43) times/min,P＜0.01) and the DH group ((469.94 ±7.36)times/min,P＜0.01).In the test of conditioned tone fear memory.The freezing time percentage in FF group ((18.78±6.29) ％) was significantly lower than that in the Sham ((51.77±9.33)％,P＜0.01) and DH group ((59.19±8.13)％,P＜0.01),but the freezing time percentage between the later two groups had no difference (P=0.52).The synchronous telemetry measurement showed there was no significant difference both in the heart rate and the blood pressure among the groups (all P＞0.05) during the conditioned tone test.Conclusion The dorsal hippocampal lesions and fimbria-fornix transection in rats can significantly reduce the learning and memory ability in conditioned fear and scene fear in rats,and the effect of fimbria-fornix transection is more obvious.The decrease in,fear memory is not synchronously reflected in heart rate and blood pressure in rats.
ABSTRACT
In the present study, the possible role of a potent cannabinoid agonist, WIN55, 212-2 in the dorsal hippocampus on pain and memory performance has been evaluated. Animals were cannulated in CA1 region of the hippocampus using sterotaxic apparatus. Ten days after recovery, animals were trained in passive avoidance learning (PAL), and immediately received different doses of WIN 55212-2 (0.1, 0.25 and 0.5µg/rat), and were tested 24 h after the training. In the second part of the experiment animals received either WIN 55212-2 (0.5µg/rat) or saline respectively. Tail flick latency was measured three times with 10 minutes interval 30 minutes and 24 hours after the infusion into the CA1. Results indicate that post-training intra-CA1 administration of WIN55, 212-2 (0.25 and 0.5µg/rat).
ABSTRACT
Aging changes of somatostatin (SS) mRNA-positive neurons in the dorsal hippocampus of old rats were studied by in situ hybridization histochemistry and image analysis. In the young rats,SS mRNA-positive cell bodies were mainly located in the pyramidal and polymorphic cell layers of the CA1 and CA2 regions, and in the strata radiatum and polymorphic cell layer of the CA3 region, and in the polymorphic cell layer of dentate gyrus. In the old rats,SS mRNA-positive cell bodies were concentrated in the polymorphic cell layer and denate gyrus. A marked decrease of number of SS mRNA-positive cell bodies and a significant increase of gray value of SS mRNA-positive cell bodies were found in the dorsal hippocampus and dentate gyrus of the old rats as compared with the young rats. No significant age difference in the sectional area of SS mRNA-positive cell bodies was observed in the dorsal hippocampus. The results showed that there were apparent changes with aging of the SS mRNA-positive cell bodies in the dorsal hippocampus of the rats. The significance of the changes remains to be studied further.
ABSTRACT
Divergent axon collaterals from forebrain and brainstem to the dorsal hippocampus in the rat were examined by means of HRP method and fluorescent retrograde double labeling method.HRP solution was injected into the left or right dorsal htppocampus of 3 rats. HRP labeled cells were observed in the bilateral medial parts of medial septal areas, vertical limbs of the diagonal band of Broca, supramammillary nuclei, submammillothalamic nuclei, superior central nucleus and locus ceruleus.PI and Bb solution were injected into the left and right hippocampus of 3 rats separately. Many retrograde double labeled cells were found in the nuclei mentioned above.The results indicate that the retrograde double labeled ceils in these nuclei may divergently projected to both the left and right dorsal hippocampi. They play an important role in harmonizing the activity of bilateral hippocampi.