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Abstract
The dorsolateral medulla, including the nucleus reticularis parvicellularis, the cuneate
nucleus, and the external cuneate nucleus, is an integrative region for a variety
of sensory inputs. The purpose of this study was to determine whether individual neurons
respond to a variety of different sensory modalities. To this end, responses of 40
neurons in the dorsolateral medulla to multiple sources of sensory input were assessed
in cats anesthetized with alpha-chloralose. Neurons were located in the nucleus reticularis
parvicellularis (24 cells, 60%), the cuneate nucleus (10 cells, 25%), and the external
cuneate nucleus (6 cells, 15%). All neurons were tested for responses to: electrical
stimulation of afferents coursing through the left stellate ganglion and afferents
in the left cervical vagus nerve, and somatic, auditory, and visual stimulation. No
neurons responded to all five stimuli. Three cells (7.5%) responded to four stimuli,
11 (27.5%) responded to three stimuli, 10 (25.0%) responded to two stimuli, and 15
(37.5%) responded to only a single stimulus. The remaining cell was unresponsive to
any stimulus. As a group, neurons in the nucleus reticularis parvicellularis received
input from the greatest number of sensory modalities, and cuneate nucleus neurons
received input predominantly from somatosensory afferents. External cuneate nucleus
neurons displayed response profiles intermediate between nucleus reticularis parvicellularis
and cuneate nucleus. In addition, eight neurons (20% of the total) were sensitive
to changes in blood pressure. Results of the present study support the hypothesis
that neurons in the nucleus reticularis parvicellularis receive convergent inputs
from different sensory modalities.2+ behaviors.