ABSTRACT
ObjectiveThe heroin-dependent animal model of rats was used to investigate the effects ofheroin on regulation of pain perception in the dorsal and ventral hippocampus of the heroin-dependent rats. Meth odsHeroin was injected subcutaneously twice a lay for 9 days according to the principle of daily increasing dose in the Sprague-Dawley rats. From the 10th day,rats were given heroin at dose of 27 mg · kg-1 once a day until the14th day, then the unit discharges of the dorsal and ventral hippocampus of rats were observed respectively afternoxious electric stimulation of the rat-tail by the extracellular single-unit recording with glass microelectrodes. ResultsWhen given noxious stimulation, most of the neurons in the dorsal hippocampus in the heroin-dependent ratswere unaffected(59.09％ ) ,whereas in the control rats ,the ratio of the neurons of the dorsal hippocampus affectedby noxious stimulation was about 66.67％, respectively(P ＜ 0.05 ). However,in the ventral hippocampus, the ratioof the neurons activated,inhibitory or unaffected was 20. 69％ ,41.38％ and 37.93％ from the control and was40.74％ ,33. 33％ and 25.93％ from the heroin group respectively with no significant difference between two groups (P ＞ 0.05 ) . ConclusionHeroin changed the regulation of pain perception in the hippocampus,primarily the dorsal hippocampus of rats.
ABSTRACT
The effects of electrical stimulation of spinal cord and nucleus tractus solitarius (NTS) on unit activity of paraventricular neucleus (PVH) in the rats were studied. The results of experiments in 105 rats showed that in the 1365 units, 67 units made responses to electrical stimulation of spinal cord, and 42 units to electrical stimulation of nucleus tractus solitarius.In the 67 units responsive to electrical stimulation of spinal cord, five kinds of ffects were observed: facilitatory, excitatory, inhibitory, inhibitory-excitatory and excitatory-inhibitory. In the 42 units responsive to electrical stimulation of nucleus ractus solitarius some showed facilitatory effects and others inhibitory effects.The results indicate that the majority of spinal inputs is conveyed to the PVH along multisynaptic pathways,while a lesser part along oligo-or mono-synaptic pathways.The results also suggest that there are multisynaptic pathways from rostral part of nucleus tractus solitarius to the PVH.
ABSTRACT
Objective To observe the modulation of met enkephalin (ME) and naloxone (NLX) on the excitatory effects of kainic acid (KA) and glutamic acid (GLU) in hippocampus of rats and to explore the possible mechanism of the effects of ME in the KA epilepsy model. Methods A total of 45 healthy Wistar rats were anesthetized with 1% sodium pentobarbital (3 ml/kg intraperitoneal injection). After endotracheal intubation, the animal was mounted onto a SN 1stereotaxic apparatus (Narishige) and routine craniotomy was performed. Then the animal was immobilized by 0.01% curare (1 mg/kg) after it woke up. The peripheral pipettes of a multiple pipette microelectrode were used for microelectrophoretic application of drugs; the central pipette was used for extracellular recording of the hippocampal unit discharges (HUDs). Results ①ME excited most of the HUDs; opioid receptor antagonist NLX could reverse the excitatory effects of met enkephalin. NLX applied alone had no effects on the firing rate of HUDs. ②KA and GLU excited the HUDs intensively but ME and NLX could modulate their excitatory effects. Conclusion ME may promote the development of epilepsy by modulating the excitatory effects of KA and GLU in hippocampus.