Frederick W. L. Kerr

Structural relation of the trigeminal spinal tract to upper cervical roots and the solitary nucleus in the cat

Abstract The relation of the descending tract of the trigeminal nerve to the upper cervical dorsal roots is of considerable physiological and clinical interest, particularly with reference to the mechanisms of hemicranial pain syndromes. This study describes in detail the distribution of trigeminal and cervical afferents in the upper cervical cord and indicates that anatomic convergence of these two systems is present throughout the dorsal horn in the first and second cervical segments. The distribution of trigeminal afferents at all brain-stem and cervical levels was studied and a contingent of fibers to the solitary nucleus was identified in every experiment. The possible significance of this in terms of function is discussed. Neurons of the semilunar ganglion do not establish direct reflex connections with motor nuclei of the brain stem; barring insignificant exceptions such connections require at least one interneuron.

The ultrastructure of the spinal tract of the trigeminal nerve and the substantia gelatinosa.

Abstract The fine structure of the spinal tract of the trigeminal nerve and the associated substantia gelatinosa as seen in transverse sections by electron microscopy at a level just caudal to the obex is described. The tract is characterized by the extremely small diameter of the myelinated fibers, by the large proportion of unmyelinated fibers and by the paucity of glial fibers. In the marginal zone of the substantia gelatinosa an unusually dense population of boutons is to be found; these establish axodendritic synapses as well as axoaxonic synapses with each other. The small neurons of the substantia gelatinosa have few axosomatic contacts on their perikarya; some of the axosomatic synapses are postsynaptic to other boutons. In contrast, there are frequent synapses on the base of their dendrites. Synapses on dendrites of the substantia gelatinosa whose source could not be determined are often profuse. These observations are discussed in the light of current neurophysiological studies.

Reciprocal (push-pull) effects of morphine on single units in the ventromedian and lateral hypothalamus and influences on other nuclei: with a comment on methadone effects during withdrawal from morphine

Abstract The effects of morphine and of its antagonists naloxone and nalorphine on multiple single units recorded simultaneously in the ventromedian nucleus (VMN) and in the lateral hypothalamic area (LHA) and certain other neuronal groups were investigated in naive and morphine dependent adult Sprague-Dawley rats using pulse height analysis techniques and computer generated firing frequency histograms. Morphine produced diametrically opposite effects on VMN and LHA in both naive and dependent animals; with the exception of a few units, neurons recorded from the VMN were excited by morphine and, conversely, those in LHA were inhibited; the antagonists naloxone and nalorphine produced clear-cut reversal of these effects. During withdrawal phases in addicted animals, firing rates in the LHA were greater than rates recorded in the same area of naive animals; no significant differences between firing rates in the VMN of naive and addicted animals were observed. Methadone effects were investigated in morphine dependent rats in withdrawal; both VMN and LHA neurons were excited by methadone and the effect of morphine on these nuclei was reversed. The possible implications of these observations for localization of mechanisms in opiate dependency and for the concept of methadone blockade are discussed.

Acupuncture reduces the trigeminal evoked response in decerebrate cats

Abstract Electroacupuncture was administered to 52 decerebrate, unanesthetized cats in which the trigeminal electrically evoked response was recorded from the surface of the brain stem. In 15 of these, the first negative wave of the evoked potential was reliably depressed by 20 to 80% after electroacupuncture, and spontaneous recovery of the responses occurred in 3 to 15 min. This is a previously unreported finding and is discussed in the light of current theories of acupuncture and analgesia.

On the question of ascending fibers in the pyramidal tract: with observations on spinotrigeminal and spinopontine fibers

Abstract In a re-evaluation of the question of an ascending fiber system in the pyramidal tract, by means of a degeneration technique using conservative criteria and normal control material, the presence of such ascending fibers could not be confirmed nor could spinotrigeminal fibers be demonstrated. A minute contingent of spinopontine fibers, which do not reach that location via the pyramidal tract, is described; it is suggested that they may ascend with the ventral spinocerebellar tract.

Synaptic Alterations in Developing Cortical Infarction: An Experimental Investigation in Monkeys

The sequential synaptic alterations which occur during the early phase of developing cortical infarction in the squirrel monkey were studied with the electron microscope. Mild swelling of a few dendritic terminals and clumping of synaptic vesicles were the earliest detectable changes, being present at 45 minutes. The two basic patterns of degeneration of the terminal boutons were shrinkage and swelling, with shrinkage being the predominant response. Many of the shrunken boutons became electron-dense, resembling the changes present in anterograde axonal degeneration. The alterations which developed in the dendritic terminals were relatively unimpressive. Disruption of axosomatic synapses occurred at an earlier stage and was more severe than that of axodendritic synapses. Reduction in the number of synaptic vesicles was first observed at six hours and appeared to be progressive. The edema which developed was morphologically distinct from both “vasogenic” and “cytotoxic” edema in that there was early and progressive enlargement of the extracellular space.

THE RESPONSE OF DOGS TO PERFUSION AND ARREST OF CIRCULATION AT NEAR ZERO CEREBRAL TEMPERATURES.

Summary o 1. Twenty-six dogs were cooled by a whole body, closed chest perfusion technique to end perfusion brain temperatures of 14.1° to 0.2° C. inclusive. 2. There were no deaths in the group of six dogs in which the end perfusion brain temperature was 10.0° C. or higher. 3. In the 17 dogs cooled to brain temperatures of 5.0° C. or less there were nine deaths, of which five occurred quickly from cardiovascular failure, while four resulted from gross neurologic disturbances. 4. There was no evidence of aortic incompetence during whole body, closed chest hypothermic perfusion. 5. The lower the temperature of the brain at the end of the cooling perfusion, the greater was the passive transfer of heat from the environment.

Effects of Freezing and Storage on Survival of Thyroid Autografts.

Summary Thyroid tissue from 8 adult dogs was autotransplanted successfully into the cerebral cortex. Histologic viability was demonstrated in all instances for as long as 2 months. Thyroid tissue from 6 adult dogs was frozen at −196°C after immersion in dimethyl sulfoxide and stored at this temperature for 2 weeks. After rapid thawing, the tissue was autotransplanted into the cerebral cortex. Histologic examination showed apparent viability of the transplanted tissue at 6 weeks (one animal) and 12 weeks (2 animals) after autotransplantation.