Journal of neurophysiology
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1. We recorded responses of low-frequency auditory nerve fibers (characteristic frequency (CF) less than 3 kHz) in the cat to resonant stimuli with varied natural frequencies, damping coefficients, and sound pressure levels. Responses to resonances were synchronized to frequencies lying between the peak frequency of the stimulus spectrum and a frequency near the fiber's CF. ⋯ Temporal patterns present in the response of a population of fibers encoded the parameters of resonant stimuli. 6. The model revcor filter bank provided a means of studying temporal response patterns of the population of fibers to other complex sounds. 7. The output of the population model is a representation of the temporal information provided by the auditory periphery to the central nervous system; thus it provides a potentially useful tool for testing hypotheses concerning the processing of temporal information by the central auditory system.(ABSTRACT TRUNCATED AT 400 WORDS)
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1. Single-unit activity was recorded from 215 neurons in the medial bulbar reticular formation during the masticatory sequence, from intake to deglutition, of 3 kinds of food (cat food pellets, canned fish, and milk) in 8 chronically prepared, unanesthetized, spontaneously respiring cats with their head fixed to a stereotaxic apparatus without pain or pressure. The firing patterns were compared to the simultaneously recorded EMGs of the jaw-closing and -opening muscles and to the jaw movement. 2. ⋯ We detected a monosynaptic excitatory projection from 3 opening-type neurons to the anterior digastric motoneurons, and monosynaptic inhibitory projections to the temporal or masseter motoneurons from 3 other opening-type neurons, by spike-triggered averaging of the full-wave rectified EMG of the jaw-closing and -opening muscles. No monosynaptic projections from the closing-type neurons or nonphasic group neurons to either jaw-opener or -closer motoneurons were detected. 5. The instantaneous firing frequency of all 3 inhibitor premotor neurons was positively correlated with the opening velocity, and the firing of 2 was also related to the jaw displacement.(ABSTRACT TRUNCATED AT 400 WORDS)
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1. In anesthetized rats recordings were made from neurons in the medulla caudal to the obex. In the medullary dorsal horn, typical trigeminal noxious specific, nonnoxious specific, and convergent neurons were found. ⋯ All the TNC neurons responded to suprathreshold percutaneous electrical stimulation (2-ms duration) with two peaks of activation no matter which part of the body was stimulated. By stimulating two regions of the tail, 100 mm apart, we determined that the early and late peaks of activation were triggered by activities in peripheral fibers with mean conduction velocities of 10.8 +/- 0.5 and 0.74 +/- 0.05 (SE) m/s, respectively, i.e., A delta- and C-fibers. The mean thresholds for obtaining A delta-fiber components were found in the 0.4-0.7-mA range; the mean thresholds for obtaining C-fiber components were found in the 6-7.5- and 3-4-mA range for the face and the other parts of the body, respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
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1. This study examines the effect on auditory desensitization of electrically stimulating the crossed olivocochlear bundle (COCB) at the floor of the fourth ventricle. Auditory desensitization was induced by a loud high-frequency pure tone exposure and measured as temporary threshold shifts (TTS) in the sensitivity of the compound action potential recorded from the cochlea. ⋯ However, if the persistent effect was at a more central location, lesioning the fibers would allow afferent input to act at the facilitated central location but would not allow subsequent expression of COCB effects at the cochlea. In this case, no reductions in TTS could be expected--precisely the results that were obtained in these experiments. Thus the COCB system appeared to have a "memory" component facilitated by prior stimulation and activated by a subsequent exposure.
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1. We have recently shown that leukotriene B4 (LTB4), a product of the 5-lipoxygenase pathway of arachidonic acid metabolism, sensitizes nociceptors to mechanical stimuli. The present study examined whether LTB4 also induces a heat sensitization of cutaneous C-fiber nociceptors. ⋯ The magnitude of the LTB4-evoked decrease in thermal threshold was similar to that produced by 75 ng of prostaglandin E2 (PGE2). These data demonstrate that LTB4 sensitizes C-mechanoheat nociceptors to both mechanical and thermal stimuli. 4. We conclude that LTB4 may contribute to the component of hyperalgesia that is resistant to nonsteroidal anti-inflammatory agents.