RESPONSES OF NEURONS IN THE PARABRACHIAL REGION OF THE RAT TO ELECTRICAL-STIMULATION OF THE SUPERIOR LARYNGEAL NERVE AND CHEMICAL-STIMULATION OF THE LARYNX

The responsiveness of the parabrachial region to electrical stimulatio n of the superior laryngeal nerve was first examined in anesthetized r ats. Action potentials were recorded in 30 parabrachial sites by singl e and train electrical pulses to the superior laryngeal nerve, The ave rage latency, from the onset of stimulation to the first action potent ials, was 9.9 ms (range, 6.5-18.8 ms). The responsiveness of parabrach ial neurons to chemical stimulation of the laryngeal region was next e xamined using anesthetized, immobilized, and artificially ventilated r ats in which the chorda tympani and glossopharyngeal nerves were bilat erally sectioned. Taste stimuli were applied to the laryngeal region t hrough a tracheal tube and rinsed with 0.15 NaCl. A total of 66 respon ses were recorded from 26 neurons. The most effective stimulus for the se neurons was 0.03 M hydrochloric acid, followed by 0.01 M quinine hy drochloride, 0.5 M sodium chloride, 0.5 M sucrose, and distilled water , Seven responses were derived from 0.15 NaCl. These neurons were main ly located in a posterodorsolateral part of the parabrachial nucleus. These results suggest that chemical signals from the laryngeal region are transmitted to the parabrachial nucleus through the superior laryn geal nerve. (C) 1998 Elsevier Science Inc.