The Journal of neuroscience : the official journal of the Society for Neuroscience
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Comparative Study
Neurotransmitter profile of saccadic omnipause neurons in nucleus raphe interpositus.
Saccadic omnipause neurons (OPNs) are essential for the generation of saccadic eye movements. In primates OPNs are located near the midline within the nucleus raphe interpositus (rip). In the present study we used several different neuroanatomical methods to investigate the transmitters associated with OPNs in the monkey. ⋯ The quantitative analysis of immunoreactive terminal-like structures contacting OPNs revealed a strong input from GLY- and GABA-positive terminals on somata and dendrites, whereas GLU-positive puncta were mainly confined to the dendrites. Very few 5-HT and catecholaminergic terminals contacted OPN somata. Our findings suggest that OPNs use GLY as a neurotransmitter, and they receive numerous contacts from GABAergic, glycinergic, and glutaminergic afferents, and significantly fewer from monoaminergic inputs.
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In a rat model of morphine tolerance, we examined the hypotheses that thermal hyperalgesia to radiant heat develops in association with the development of morphine tolerance and that both the development and expression of thermal hyperalgesia in morphine-tolerant rats are mediated by central NMDA and non-NMDA receptors and subsequent protein kinase C (PKC) activation. Tolerance to the analgesic effect of morphine was developed in rats utilizing an intrathecal repeated treatment regimen. The development of morphine tolerance and thermal hyperalgesia was examined by employing the tail-flick test and paw-withdrawal test, respectively. ⋯ MK 801 (5, 10 nmol, not 2.5 nmol) and CNQX (80, 160 nmol, not 40 nmol), but not GM1 (160 nmol), also reliably reversed thermal hyperalgesia in rats rendered tolerant to morphine when tested 30 min after each drug treatment on day 10 (48 hr after the last morphine treatment). The data indicate that thermal hyperalgesia develops in association with the development of morphine tolerance and that the coactivation of central NMDA and non-NMDA receptors is crucial for both the development and expression of thermal hyperalgesia in morphine-tolerant rats. Furthermore, intracellular PKC activation plays a critical role in the development of thermal hyperalgesia in morphine-tolerant rats.(ABSTRACT TRUNCATED AT 400 WORDS)