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Biomedical subjects

J T Cannon

Publications and source records attributed to J T Cannon.

12 recordsLinked to original sources
PubMed1991

Stimulation of the periaqueductal gray matter of the rat produces a preferential ipsilateral antinociception.

The few studies analyzing somatotopic organization of stimulation-produced antinociception (SPA) from the periaqueductal gray matter (PAG) have reported contradictory results. In the present study, the distribution of SPA on the hindquarters was assessed by measuring the threshold for inhibition of withdrawal reflexes to noxious heat applied to the hindpaws and tail in pentobarbital-anesthetized rats. Of the 3 body regions tested, the hindpaw contralateral to the stimulating electrode required the highest level of PAG stimulation to inhibit withdrawal. Reducing the intensity of the heat stimulus applied to the hindpaws caused a concomitant reduction in SPA threshold. As before, a higher stimulation current was needed to inhibit the withdrawal reflex in the contralateral than in the ipsilateral paw. These data indicate the antinociception from PAG stimulation is not equally distributed throughout the body, and that the intensity of the noxious stimulus influences the threshold for SPA.

Animals↗
PubMed1984

Intrinsic mechanisms of pain inhibition: activation by stress.

Portions of the brain stem seem normally to inhibit pain. In man and laboratory animals these brain areas and pathways from them to spinal sensory circuits can be activated by focal stimulation. Endogenous opioids appear to be implicated although separate nonopioid mechanisms are also evident. Stress seems to be a natural stimulus triggering pain suppression. Properties of electric footshock have been shown to determine the opioid or nonopioid basis of stress-induced analgesia. Two different opioid systems can be activated by different footshock paradigms. This dissection of stress analgesia has begun to integrate divergent findings concerning pain inhibition and also to account for some of the variance that has obscured the reliable measurement of the effects of stress on tumor growth and immune function.

Adaptation, Physiological↗
PubMed1984

Body region shocked need not critically define the neurochemical basis of stress analgesia.

Both opioid and non-opioid forms of stress-induced analgesia have been demonstrated in rats, although the conditions leading to their selective activation are still being investigated. We have shown that variations in shock intensity, duration or temporal pattern can determine whether opioid or non-opioid stress analgesia occurs. Others have suggested that body region shocked is the critical determinant, analgesia from front paw shock being opioid and that from hind paw shock non-opioid. We now report that either opioid or non-opioid stress analgesia can be evoked from either front or hind paws depending only on footshock intensity when duration and temporal pattern are held constant.

Animals↗
PubMed1983

N. raphe magnus lesions disrupt stimulation-produced analgesia from ventral but not dorsal midbrain areas in the rat.

We previously found that the opiate antagonist, naloxone, partially blocks stimulation-produced analgesia (SPA) elicited from ventral but not dorsal regions of the medial midbrain in rats. The present study compares the effects of n. raphe magnus (NRM) lesions on SPA from these same two midbrain areas. SPA thresholds were measured with the tail-flick method and compared before and for up to two weeks after NRM lesions. A high positive correlation was found between percent NRM destruction and percent increase in SPA threshold for rats with ventral but not dorsal electrode placements. Damage to brain areas other than NRM seemed not to contribute to these effects. We conclude that n. raphe magnus is a critical relay in the pain-suppressive path from that area of the rat midbrain mediating an opioid form of stimulation-produced analgesia.

Animals↗
PubMed1981

Effects of naloxone and hypophysectomy on electroconvulsive shock-induced analgesia.

Powerful analgesia follows electroconvulsive shock in both hypophysectomized and sham-operated rats. Antagonism of this analgesia by naloxone implicates opioid peptides in its mediation, its occurrence in hypophysectomized animals implicating opioids of central nervous system rather than pituitary origin. Because naloxone only partially reduces electroconvulsive shock analgesia in hypophysectomized rats, the participation of another, non-opioid analgesia substrate also seems indicated.

Animals↗
PubMed1978

Long ascending projections from substantia gelatinosa Rolandi and the subjacent dorsal horn in the rat.

Small neurons of the substantia gelatinosa Rolandi and the subjacent dorsal horn of the spinal cord have been thought to exert a direct modulatory effect only on neurons located within a distance of a few spinal segemnts. By using the technique of retorograde transport of horseradish peroxidase, however, it has been found that in the rat a significant number of these cells, particularly those of the subjacent dorsal horn, ascend many spinal segments to the lateral cervical nucleus and to the lower brainstem. These data provide an anatomic basis for a role of substantia gelatinosa Rolandi and subjacent dorsal horn cells in madulating or contributing to sensory information transmission not only in nearby segments but in far distant structures.

Afferent Pathways↗
PubMedDate not supplied

Guild--name changes!

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Catholicism↗