| 其他摘要 | The research parts of this thesis include "The effects of orbitofrontal cortex on morphine-induced drug dependence in rats"(Part I) and "Telemetric recordings of single neuron activity and visual scenes in monkeys walking in an open field"(Paxt II). Part I In this part, we investigated the effects of orbitofrontal cortex (OFC) on morphine-induced addiction. Several lines of evidence suggest that OFC contributes to compulsive drug seeking. However, we did not know whether the OFC would either facilitate or inhibit morphine-induced addiction. In people, dysfunction of OFC is associated with disturbances in motivation and an inability to anticipate consequences, leading to poor judgment and maladaptive behaviors that may depend in part on the conditioned reinforcement process. Then, we want to know the effects of electrolytic lesions of lateral OFC on the morphine-induced addiction. In addition, it is well known that DAD2 receptor plays a role important in mediating drug-induced addiction. Also, the effect of DA D2 receptors in the OFC on morphine-induced addition was unknown. Furthermore, evidence suggests that systemic administration of baclofen in morphine-dependent rats can attenuate the withdrawal signs. However, we did not know whether the activation of GABAB receptors in the OFC block or inhibit the incentive effects of morphine or morphine -induced craving. Based on above problems, our experiments were focused on these three topics in a rat model of addiction process. In this part, the effects of OFC lesions, microinjections of a GABAB receptor agonist-baclofen into OFC and microinjections of DA D2 agonist or antagoist into OFC on morphine-induced addiction were investigated using the conditioned place preference (CPP) paradigm in rats. First, the results indicate that OFC lesions before conditioning failed to prevent morphine-induced conditioned place preference, suggesting that OFC is not essential for associative learning between environmental cues and the hedonic experience of morphine. In contrast, OFC lesions after conditioning enhanced CPP, suggesting that OFC modulates the propensity for morphine seeking and the OFC plays a critical role in assessing the current motivational significance of drug-conditioned stimuli if stimulus-reward learning occurs before OFC lesions. Second, the results indicate that the DA D2 system in OFC modulates the propensity for morphine seeking and the decrease of the DA D2 system activities in OFC would enhance morphine -induced craving. Thirdly, it is concluded that activation of orbitofrontal cortex GABA B receptors involve in modulating the acute rewarding effects of morphine but not morphine -induced craving. Part II In the second part, we want to introduce how to develop the methods of telemetric recordings of single neuron activity and visual scenes in monkeys walking in an open field. Extracellular recording of the unit activities from a single neuron is a major and popular method in animals to study the sensory, motor and cognitive functions of the brain in cellular level and it plays a very important role in understanding the relationships of brain and behavior. However, with traditional recording systems some recording apparatus limit the area in which the subjects could walk and do not permit the manifestation of many natural behaviors; Thus, single unit recordings suffered from great limiting factors in the studies of the relationship of brain and behavior particularly in the studies of motor function. By modifying traditional recording systems we have developed a portable recording system and methods for obtainmg chronic recordings of single units and tracking rhesus monkey behavior in an open field. With this method, we are able to record the electrical activity of a single neuron that can last for several hours with high signal-noise ratio from the freely moving monkeys. During the entire recording process, monkey can move freely in the open field and thus minimized stress from the experiment. While the electrical activities for neurons were recorded, the animal behaviors were also monitored. In developing our method, several factors were important. These factors included designing (Da movable microelectrodes, (2) using a small and light amplifier, and (3) signals transmitted by a wireless system .The described methods provide a new way to examine correlations between single neuron activity and primate behaviors, and can also be used to study the cellular basis of social behaviors in non-human primates. |
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