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R N Weber

Publications and source records attributed to R N Weber.

6 recordsLinked to original sources
PubMed1984

Viscerosomatic convergence onto T2-T4 spinoreticular, spinoreticular-spinothalamic, and spinothalamic tract neurons in the cat.

Neurons of T2 to T4 spinal segments were antidromically activated from the medullary reticular formation and the contralateral region in or near the ventral posterior lateral nucleus of the thalamus. Sixty-seven percent of the spinoreticular neurons projected to the ipsilateral, contralateral, or both ipsilateral and contralateral medullary reticular formation. In addition, 21% of the cells projected to the reticular formation and thalamus and 12% projected only to the thalamus. These cells received both visceral and somatic inputs. Electrical stimulation of cardiopulmonary sympathetic afferent fibers elicited an early peak of cell activity in 30 cells, an early and late peak in 38 cells, and only a late peak in 1 cell. Seventy-one percent of the cells had simple somatic receptive fields; these fields were localized to the left forelimb and left upper thorax. The remaining 29% of the cells had complex receptive fields that often extended to the hind limb as well as bilaterally. Classification of all cells according to threshold for activation of the somatic receptive field showed that 86% of the cells were high-threshold, 10% were wide dynamic range, and 4% were high-threshold but, in addition, were inhibited during hair movement. Viscerosomatic convergence onto these cells support Ruch's convergence projection theory for referred pain. These projecting neurons may be involved with referred pain associated with angina pectoris. In addition, they may also be involved with cardiovascular adjustments.

Animals↗
PubMed1984

Responses of thoracic spinoreticular and spinothalamic cells to intracardiac bradykinin.

The response characteristics of spinoreticular and spinothalamic cells to intracardiac injection of bradykinin were determined in cats anesthetized with chloralose. Extracellular potentials of individual spinoreticular and spinothalamic cells were recorded from the T2-T4 segments of the spinal cord. Only those cells with cardiopulmonary sympathetic afferent input were tested for responses to intracardiac bradykinin (1-6 micrograms/kg). Thirty-seven of the 64 cells studied responded to bradykinin; 36 were excited and one was inhibited. For excited cells, discharge rate increased from 4 +/- 1.0 (SE) spikes/s to a peak of 20 +/- 2.4 spikes/s, a fivefold increase. Latency to onset of cell response was 13 +/- 1.1 s, and latency to peak response was 24 +/- 1.4 s after drug injection. Tachyphylaxis to additional doses of bradykinin was observed in 17 of 32 cells. Occurrence of tachyphylaxis was sometimes altered after bilateral cervical vagotomy. The projection sites in the caudal medulla and thalamus were similar for responsive and nonresponsive cells. Laminar cell locations in the spinal cord had no significant influence on likelihood of cell response to bradykinin. We conclude that spinoreticular and spinothalamic cells have a role in transmitting noxious information from the heart to the brain.

Animals↗
PubMed1982

Responses of thoracic spinothalamic neurons to intracardiac injection of bradykinin in the monkey.

Bradykinin stimulates afferent fibers arising in the heart and may be involved in the mediation of anginal pain and the pain associated with myocardial infarction. The sensation of pain requires that noxious information reach the brain. The purpose of the present study was to determine whether the spinothalamic tract is involved in transmitting noxious information from the heart to the brain. Bradykinin was injected (0.3-3.5 micrograms/kg) into the heart via a catheter in the left atrium while we recorded from single spinothalamic cells in the C8 to T5 spinal segments. Thirty-one of 41 cells responded to bradykinin. The responses of 12 cells were characterized by both an increase in discharge rate and entrainment of cell activity with the cardiac cycle. Eighteen cells responded with only an increased rate, and one cell exhibited only entrainment of cell activity with the cardiac cycle. The mean onset of increased cell activity occurred 15 seconds following drug injection, and the average duration of the response was 54 seconds. Thirty cells increased their mean discharge rate from 11 +/- 2.5 to 29 +/- 4.4 spikes/second. Thus, some spinothalamic cells probably received input from both mechanosensitive and chemosensitive afferents. Tachyphylaxis to repeated doses of bradykinin was observed in 41% of cells. Cells responding to bradykinin had a spontaneous discharge rate that was significantly greater than that of nonresponding cells. Cells did not require input from C-fiber afferents to respond to bradykinin. No statistically significant relationships were found among anatomical locations (laminae and segments) and responses to bradykinin, although cells in lamina I seemed to be less responsive than more ventrally located cells. We conclude that the spinothalamic tract may be involved in the sensation of cardiac pain.

Afferent Pathways↗