1. A STUDY ON MODULATION FROM SACCADIC SYSTEM ON PUPILLARY LIGHT REFLEX SYSTEM 2. SPONTANEOUS FIRING PATTERNS OF INSULAR NEURONS DURING NALOXONE TREATMENT IN ANESTHETIZED MORPHINE-DEPENDENT RATS
Part 1. A primary study on modulation from saccadic system on pupillary light reflex system The saccadic system is beautiful model for studying the neural control of movements. The pupillary light reflex (PLR) is the constriction of the pupil that is elicited by an increase in illumination of the retina. Previous studies illustrated that two systems are not closed. It is unknown that whether the saccadic system modulates the PLR system. This experiment investigated changes of latency and pupil diameter in PLR in fixation station and saccadic station. The results showed the latency of PLR on fixation station and during saccades are significantly different. Two horizontal saccades, abduction and adduction， change the latencies and relative pupil constriction ratio of PLR in different ways. The latency decreased when abduction occurred during PLR process and increased when adduction occurred. Compared with fixation station, abduction increased the relative constriction ratio of pupil while adduction decreased it. Although saccade induces pupil constriction, the relative constriction ratio is not equivalent to the change of pupil diameter in PLR process which saccades occurred. It is concluded that change of pupil diameter is not attributed to simple addition of effect of light and saccade during PLR in saccadic station. Further analysis based on saccades occurring time showed saccade occurring in different periods changed the latency and the relative constriction ratio of pupil constriction in different ways. Our data illustrated that two systems are not independent, and the saccadic system modulates PLR system. Part 2. Spontaneous firing patterns of insular neurons during naloxone treatment in anesthetized morphine-dependent rats Drug addiction is considered as a chronic, recurrent brain disease characterized by relapse. Previous studies showed insular cortex is involved in addiction. In the current study, Conditioned place preference（CPP） paradigm was used to test the dependence and psychological craving for morphine. Rats received alternate-day morphine/saline (10mg.kg-1.day-1, ip) injection for six days. Multiple electrode recordings were used to examine the neuronal activities in insular and somatosensory cortex between pre- and post- naloxone treatment in anesthetized rats in post-conditioning days. Compared with the control group, 71.43% of insular neurons recorded displayed significant increase on spike firing after naloxone treatment. In insular cortex, the mean firing rate of increased firing neurons did not show significant difference in contrast to the control group. Firing patterns of neurons from two areas are different by Chi-square test. The results indicated that not all brain areas but special brain areas were activated during morphine craving in morphine addiction. Our data provided a proof at neuronal level that insular cortex participates in morphine dependence.
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