Morphometric studies on the microvasculature of pre- and paravertebral sympathetic ganglia in the adult and aged rat by light and electron microscopy

Abstract

Morphometric measurements have been made by light and electron microscopy on sections of perfused sympathetic ganglia from rats of 6-24 months of age with special reference to the microvascular bed. Capillaries, postcapillary venules and small venules comprised the majority of the vessels studied but small arterioles were, in addition, included in the light microscopical part of the study. Light microscopical measurements using image analysis showed that there was a decrease in the density of the microvascular bed (number of vascular profiles/area) and in the total vascular luminal area with age in both ganglia. The ratio of neurons to microvessels remained constant in the superior cervical ganglion (SCG) but decreased with age in the coeliac-superior mesenteric ganglion (CSMG). However, the distribution of microvessels in relation to individual neurons remained unchanged throughout life in both ganglia. Ultrastructural studies revealed fenestrations in 12% of SCG microvessel profiles and in 38% of CSMG microvessels at 6 months, but the percentage of fenestrated profiles in the CSMG had declined by 24 months. There were no significant differences in the number of fenestrations per fenestrated profile. The basal lamina surrounding the microvessels increased significantly (almost doubling) in thickness with age. The range and distribution of microvessel wall thicknesses, expressed as harmonic mean wall thickness, were comparable in both ganglia at both ages and increased linearly according to the amount of pericyte covering present. No consistently significant relationships could be discerned between the microvessel wall thickness and luminal diameter or between the wall thickness and the area available to a given volume of blood for exchange of metabolites (luminal perimeter/luminal area). We conclude that the ganglionic capillary bed is similar in both ganglia and, in old age, accommodates structural changes that occur in the ganglion by maintaining its structure and relationship to individual neurons.

There is no relation between the fascicular and the endoneural blood vessel areas on the cervical vagus nerve of normotensive rats

“…There was an obvious decrease in this percentage with ageing. These results are similar to the decrease in the density of the microvascular bed and in the total vascular luminal area observed in the pre-and paravertebral sympathetic ganglia in aged Wistar rats (Baker et al, 1989). Also, this is in agreement with observations on normal sural nerves in man (Giannini and Dyck, 1993) and this decrease might be a normal feature of ageing nerves.…”

“…The intraneural vascular pattern is subject to a wide range of variation from level to level and subject to subject and there is no pattern which is constant or characteristic for any part of the nerve (Sunderland, 1978). Quantitative approaches to the study of the microvasculature in the peripheral nervous system have been rarely described (Baker et al, 1989) and, despite some studies involving somatic nerves (Macarian and Smith, 1968;Bell and Weddell, 1984b) and autonomic ganglia (Baker et al, 1989;, information on autonomic nerves are scanty. Also, the literature provides information on number , permeability (Wadhwani et al, 1991) and ultrastructure (Bell and Weddell, 1984b; of the peripheral nerves vessels, with no information on the relation between nerve fascicles size and age, as on the blood vessels behavior with this relation.…”

Light, electron, and confocal microscopic study of the mouse superior mesenteric ganglion

“…and prevertebral ganglia of other animals was the appearance of its intraganglionic blood vessels. Fenestrated blood vessels, commonly found in prevertebral ganglia of rat and guinea pig (Al-Khafaji et al, 1980;McDonald and Blewett, 1981;Baker et al, 1989) were not found in the mouse S.m.g. All blood vessels examined in the mouse S.m.g.…”

VEGF is required for the maintenance of dorsal root ganglia blood vessels but not neurons during development

“…Many capillary beds have similarly been shown to maintain a source of VEGF even into adulthood (29). The persistence of VEGF expression in the DRG suggests that VEGF may serve functions other than direct support of vascular integrity in the adult DRG: one possible role is the maintenance of capillary network fenestrae, as have been shown to exist in other paravertebral ganglia (41).…”