Topology of sites concerned with circulatory and respiratory regulation in the lateral parabrachial nucleus of cats

s21

FIELD POTENTIALS EVOKED BY VAGAL NERVE STIMULATION IN THE RAT INSULAR CORTEX. SHIN-ICHI ITO, Department of physiology, Kumamoto University Medical School, Honjo 2-2-1, Kumamoto City, Kumamoto, 860, Japan. To identify the vaqal nerve projection areas in the rat insular cortex, field potentials evoked by electrical stimulation of both sides of the cervical vagal trunk were mapped with a surface electrode. Animals were anesthetized with sodium amobarbital, immobilized, and artificially ventilated. Recordings were made on the left hemisphere. The response consisted of several components, but only the earliest one was studied in detail. It was a negative wave with the latency of ca. 40ms. With this negativity was found to reverse in polarity at 200-400um below depth recording, the cortical surface. Thus this component represents the EPSPs produced in the superficial layers. No systematic difference in area or component was noticed between the ipsi- and contralaterally-evoked response. The latency was often shorter for the contralateral response. The response amplitude was largest at 2mm above and l-2 mm anterior to the crossing of the rhinal sulcus and middle cerebral artery. Histologically this area proved to be the granular insular cortex including the transitional zone at both its dorsal and ventral border. Smaller responses were recorded rostrocaudally in a lengthy extent along this cytoarchitectonic area. These results suggest that insofar as the earliest component is concerned, the visceral i.nformatjnn projects to the granular insular cortex longitudinally with considerable overlaps with gustatory and somatosensory areas.

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MITSUHIKO

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University

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MIURA

of

AND AND

RESPIRATORY

KIYOSHIGE

Medicine,

3-39-22

REGULATION

TAKAYAMA,

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Showa-machi.

THE of

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Physiology

Maebashi-shi.

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SYNAPTIC CONNECTIONS FRO? DECREMENTING At@ CONSTANT INSPIRArfyRY NEURONS IN CAT MEDULL 4. ,KAZUHISA EZURE , MOTOMU MANABE , KAZUYOSHI OTAKE , AND HIROSHI SASAKI , Tokyo Metrpp olitan Institute for Neurosciences, 2-6 Musashidai, Fuchushi, Tokyo 183, and LTokyo Medical and Dental University, Yushima 1-5-45, Bunkyo-ku, Tokyo 113, Japan. In pentobarbital-anesthetized, immobilized and artificially ventilated cats, we studied the connectivity of 39 burst inspiratory (I) neurons which showed non-augmenting (either decrementing (I-DEC) or constant (I-CON)) firing patterns. The activity of I-DEC and I-CON neurons was recorded in the Botzinser comolex (BOT) and the ventral respiratory group (VRG). Only 3 of the 39 I-neuron's could be antidromically activated from the spinal cord at C4-5. All 39 were antidromically activated from the contralateral medulla (the BOT, the VRG, and the dorsal respiratory group (DRG)). With spikes of either I-DEC or I-CON neurons as triggers, we performed spike-triggered averaging of synaptic potentials recorded intracellularly from respiratory neurons in the contralateral medulla. Spikes of 17 I-DEC neurons evoked monosynaptic IPSPs in 14 VRG I neurons (11 bulbospinal; 3 propriobulbar), 3 DRG bulbospinal I neurons, 3 BOT expiratory (E) neurons (1 bulbospinal; 2 propriobulbar), and 11 caudal VRG E neurons (8 bulbospinal; 3 propriobulbar). Spikes of 8 I-CON neurons evoked monosynaptic EPSPs in 8 VRG I neurons (2 bulbospinal; 3 propriobulbar; 3 vagal motoneurons) and 3 DRG I neurons (2 bulbospinal; 1 propriobulbar).