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The induction of pain: an integrative review

On the significance of subterritories in the “accumbens” part of the rat ventral striatum

• Recent clinical and research reports suggest that the cerebellum may contribute to the modulation of higher order behavior. This article presents a critical review of both earlier and more current clinical observations that raise this possibility, as well as a review of the salient laboratory data that appear to support this contention. It also summarizes the relevant anatomic work concerning the contributions to the cortico-pontocerebellar pathways from the higher order cerebral association areas, which have been implicated as partial anatomic substrates for this putative cerebellar role in higher function. Finally, it provides a framework for the understanding of this correlation, concludes with suggestions for future areas of investigation, and recommends that patients with cerebellar lesions be studied from a neurobehavioral point of view.

An emerging concept. The cerebellar contribution to higher function.

Salient features of synaptic organisation in the cerebral cortex

The central distributions of gustatory and non-gustatory branches of cranial nerves V, VII, IX, and X were examined after application of horseradish peroxidase to the cut nerve. The nerves conveying gustatory information, chorda tympani (CT), greater superficial petrosal (GSP), lingual-tonsilar branch of IX (LT-IX), superior laryngeal branch of X (SL), distributed primarily to the lateral division of the nucleus of the solitary tract (NST) from its rostral pole to the obex. The CT and GSP distributions were coextensive and terminated most densely in the rostral pole of NST. The LT-IX distribution concentrated between this major CT/GSP distribution and the area postrema with a caudal extension into the interstitial nucleus of NST. This nerve also had a substantial projection, not found in other gustatory nerves, into the dorsolateral aspect of the medial NST. The SL distribution overlapped LT-IX in the caudal medulla. The lingual and inferior alveolar nerves, two oral trigeminal branches, projected to regions of NST innervated by the gustatory nerves. The cervical vagus nerve distributed primarily to the medial NST in the caudal half of the nucleus and exhibited only minimal overlap with gustatory nerve distributions. The nucleus of the solitary tract appears to have two major functional divisions--an anterior-lateral oral-gustatory half, and a posterior-medial visceral afferent half.

Central projections of gustatory nerves in the rat

Contralateral projection of primary afferent fibers to mammalian spinal cord.

Cells of origin of propriospinal connections to cat lumbosacral gray as determined with horseradish peroxidase

The North American oppossum is born 12 to 13 days after conception and and is available for 90 days or more in an external pouch where it can be observed and experimentally manipulated. It is of particular interest that the hindlimbs of the newborn opossum are very immature and remain immobile for a week or more after birth. Degeneration techniques reveal that immature brainstem axons are present within the marginal zone of the lumbosacral cord before hindlimb movements begin (our state I) and material processed for formaldehyde induced fluorescence shows that some of them transport monoamines. Several lines of evidence suggest that part of the fluorescent axons arise within the nucleus locus coeruleus. At this early stage the electron microscope reveals that all brainstem-spinal axons are small (0.1--0.4 micrometer in diameter) and unmyelinated. By the time random hindlimb movements can be observed (stage II), brainstem axons, including those transporting monoamines, can be demonstrated to have grown into limited areas of the intermediate zone of the lumbosacral cord and to arise from most of the areas contributing to them in the adult animal (horseradish peroxidase technique). Such axons are still immature and it is not yet clear that they have formed synaptic terminals. Brainstem axons continue to grow into the intermediate zone of the lumbosacral cord for some time and come to occupy all of their adult territories before thoracic transection produces obvious change in hindlimb motility (beginning of stage III). It is still another 20 days or so before thoracic transection produces spinal shock comparable to that in the adult animal. The relatively mature use of the hindlimbs and the full expression of spinal shock correlate with changes in the technique and survival time needed to demonstrate degenerating brainstem axons in experimental material.

Observations on the development of brainstem-spinal systems in the north american opossum†

Influence of hypothalamic stimulation on the secretion of adrenal medullary catecholamines

The cytoarchitecture of the opossum basolateral amygdala was studied using Golgi techniques. The neuronal morphology was similar in all nuclei of the basolateral complex, an three distinct cell classes were recognized. Class I neurons, which vary in size in different nuclei, have spiny dendrites and long, projection axons. Axon hillocks and initial axonal segments often have spinous protrusions, while more distal portions of the axon give off several beaded collaterals that arborize primarily in the vicinity of the cell. Class II neurons are smaller, spine-sparse cells that are found in all nuclei of the basolateral amygdala but are greatly outnumbered by class I neurons. Axons branch and give off beaded collaterals which form a moderate to dense arborization within the dendritic field of the cell. Class II neurons exhibit considerable morphologic variability including one subtype that resembles the chandelier cell of the cerebral cortex. Varicosities (1.0 - 1.5 micrometers swellings) found along the axonal collaterals of these amygdaloid chandelier cells do not have a uniform distribution but tend to be aggregated. Segments of the collaterals displaying such clustered varicosities sometimes form nest-like entanglements. Clusters of varicosities have been observed forming multiple contacts with initial segments of class I axons. Class III neurons are neurogliaform cells which have many short, varicose dendritic branches that contact dendrites of class I neurons. Only the initial portions of their axons were impregnated. This study indicates that many of the cell types seen in the generalized, metatherian opossum are similar to those described in more specialized, placental mammals. This is the first description of amygdaloid chandelier cells and their contacts with the spiny initial segments of class I projection neurons.

James L. Culberson

Papers

Contralateral projection of primary afferent fibers to mammalian spinal cord.

Cells of origin of propriospinal connections to cat lumbosacral gray as determined with horseradish peroxidase

Observations on the development of brainstem-spinal systems in the north american opossum†

Influence of hypothalamic stimulation on the secretion of adrenal medullary catecholamines

Neurons of the basolateral amygdala: A Golgi study in the opossum (Didelphis virginiana)