The descending projections of the periaqueductal gray (PAG) have been studied in the rat using the anterograde tracer Phaseolus vulgaris-leucoagglutinin. The tracer was injected into the dorsolateral or ventrolateral subdivisions of the PAG at rostral or caudal sites. It was found that the patterns of the descending projections of the rostral and caudal parts of the dorsolateral PAG were the same and that the patterns of the descending projections of the rostral and caudal parts of the ventrolateral PAG were the same. However, the patterns of projections of the dorsolateral and ventrolateral PAG subregions were substantially different. These results suggest that the dorsolateral and ventrolateral parts of the PAG are organized into longitudinal columns that extend throughout the length of the PAG. The axons of PAG neurons descended through the pons and medulla via two routes. A small fiber bundle was present in the periaqueductal gray and in the periventricular area. This bundle distributed fibers and terminals locally within the periaqueductal gray and in the locus coeruleus and Barrington's nucleus. A larger bundle had a diffuse arrangement in the pontine reticular formation, however, and it had a more restricted distribution in the medulla, where it occupied a position dorsolateral to the pyramid. This bundle supplied structures in the pontine and medullary tegmentum. The dorsolateral column preferentially supplied the locus coeruleus, subcoeruleus, the gigantocellular nucleus pars alpha, the rostral part of the paragigantocellular nucleus, and the region of the A5 noradrenergic cell group. The ventrolateral column preferentially supplied the nucleus raphe magnus, the caudal part of the lateral paragigantocellular nucleus, and the rostroventrolateral reticular nucleus.

This study has examined the ascending projections of the periaqueductal gray in the rat. Injections of Phaseolus vulgaris-leucoagglutinin were placed in the dorsolateral or ventrolateral subregions, at rostral or caudal sites. From either region, fibers ascended via two bundles. The periventricular bundle ascended in the periaqueductal and periventricular gray matter. At the posterior commissure level, this bundle divided into a dorsal component that terminated in the intralaminar and midline thalamic nuclei, and a ventral component that supplied the hypothalamus. The ventral bundle formed in the deep mesencephalic reticular formation and supplied the ventral tegmental area, substantia nigra pars compacta, and the retrorubral field. The remaining fibers were incorporated into the medial forebrain bundle. These supplied the lateral hypothalamus and forebrain structures, including the preoptic area, the nuclei of the diagonal band, and the lateral division of the bed nucleus of the stria terminalis. The dorsolateral subregion preferentially innervated the centrolateral and paraventricular thalamic nuclei and the anterior hypothalamic area. The ventrolateral subregion preferentially innervated the parafascicular and central medial thalamic nuclei, the lateral hypothalamic area, and the lateral division of the bed nucleus of the stria terminalis. Although the dorsolateral and ventrolateral subregions gave rise to differential projections, the projections from both the rostral and caudal parts of either subregion were similar. This suggests that the dorsolateral and ventrolateral subregions are organized into longitudinal columns that extend throughout the length of the periaqueductal gray. These columns may correspond to those demonstrated in recent physiological studies.

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The nasal and the paranasal sinuses are a rare site for solitary fibrous tumours. There have been no previously reported cases in the English literature, with eight cases in the world literature (Witkin and Rosai, 1991; Zuckerberg et al., 1991). We present a case of a solitary fibrous tumour arising in the nasal cavity and review the previous reports.

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SummaryPharmacologic stress-testing using adenosine is increasing in popularity. Sideeffects have been limited to the infusion time and a brief recovery period. Longlasting complications may, however, result rarely.