Journal of neurophysiology
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1. The aim of this study was to utilize new quantitative behavioral methods in rats to investigate the effects of electrical stimulation in midbrain analgesia areas on the magnitude of flexion hindlimb withdrawal and tail flick reflexes evoked by graded noxious heating. Electrophysiological experiments were then done with the use of these animals to correlate behavioral data with the effects of identical midbrain stimulation on sacral dorsal horn neuronal responses to graded heating of the tail. 2. ⋯ Limb withdrawal EMG magnitude increased monotonically from threshold (approximately 40 degrees C) to 52 degrees C. The population stimulus-response function was fit equally well by linear regression or a 2 degrees polynomial function (r2 = 0.79 for both). PAG stimulation significantly reduced the mean slope of the stimulus-response function (to 73%; n = 15), whereas LRF stimulation shifted it toward the right with a smaller slope reduction (to 85%) and 3 degrees C increase in threshold.(ABSTRACT TRUNCATED AT 400 WORDS)
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1. Because the nucleus reticularis gigantocellularis (NRGc) receives a substantial descending projection from the caudal vestibular nuclei, we used extracellular single-unit recording combined with natural vestibular stimulation to examine the possible peripheral origins of the vestibularly modulated activity of caudal NRGc neurons located within 500 microns of the midline. Chloralose-urethan anesthetized rabbits were stimulated with an exponential "step" and/or static head-tilt stimulus, as well as sinusoidal rotation about the longitudinal or interaural axes providing various combinations of roll or pitch, respectively. ⋯ The activity of neurons in the medial aspect of the caudal NRGc of rabbits was modulated by both otolithic macular and vertical semicircular canal receptor stimulation. This vestibular information may be important for controlling the intensity of the muscle activity in muscles such as neck muscles where the load on the muscle is affected by the position of the head with respect to gravity. Some of these neurons may also shift muscle function from an agonist to an antagonist as the direction of head tilt changes.
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1. Electroolfactorgram (EOG) recordings were made from different regions of the rat olfactory epithelium to test for spatial distribution of odor responses. 2. The EOG recordings showed spatial distribution of the odor responses in the olfactory epithelium. ⋯ The responses to other odors (e.g., hexane or limonene) were not greatly affected by flow rate or sniff duration. 7. Taken with existing anatomic data, the results indicate that the primary olfactory neurons that project axons to glomeruli in different parts of the olfactory bulb are responsive to different odors. The latency differences between responses at medial and lateral sites are large enough to be physiologically significant in the generation of the patterned responses of olfactory bulb neurons.