Basilar Artery of the Capybara (Hydrochaeris hydrochaeris): an Ultrastructural Study

Abstract

The present study investigated the ultrastructural features of the basilar artery of the largest rodent species, the capybara. The study suggests that the general ultrastructural morphological organization of the basilar artery of the capybara is similar to that of small rodents. However, there are some exceptions. The basilar artery of the capybara contains a subpopulation of 'granular' vascular smooth muscle cells resembling monocytes and/or macrophages. The possibility cannot be excluded that the presence of these cells reflects the remodelling processes of the artery due to animal maturation and the regression of the internal carotid artery. To clarify this issue, more systemic studies are required involving capybaras of various ages.

Immunoreactive Endothelin-1 and Endothelin A Receptor in Basilar Artery Perivascular Nerves of Young and Adult Capybaras

“…In young capybaras, the fine structure of perivascular nerves, consisting of axons and Schwann cells, recorded in this study agrees with the previously observed features of cerebrovascular nerves in this animal [Islam et al, 2004] or autonomic nerves in general [Burnstock and Iwayama, 1971]. Hence the presence of characteristic both agranular and granular vesicles in axon varicosities and the appearance of Schwann cells were classic.…”

“…This study also revealed that the ET-1-positive perivascular nerves, including both axon profiles and accompanying Schwann cells, underwent changes at animal maturation coinciding with ICA regression. Our findings, therefore, supplement our previous data on the fine structure of the BA in capybaras and to the artery changes during animal maturation and ICA regression [Islam et al, 2004;Loesch et al, 2005;Steele et al, 2006]. It should be mentioned, however, that it has previously been demonstrated that in a large proportion of capybaras at maturation (which is at about 1 year of age), the ICA is no longer functioning efficiently due to the collapsed lumen, decreased lumen size and transformation to a ligamentous cord.…”

“…Perivascular Nerves: Standard TEM Both young and adult capybara BA showed characteristics of a cerebral artery consisting of 3 main histological layers namely the intima with its endothelium, the media with its vascular smooth muscle cells and the adventitia with its perivascular autonomic nerves (for more details, see a previous study from our laboratories: [Islam et al, 2004]). …”

“…Alternatively, these features of altered perivascular nerves might represent 'apparent degeneration' followed by perivascular nerve recovery, as can be observed in diabetic autonomic neuropathy for example [Monckton and Pehowich, 1980]. Notably, it has been reported that the BA of 1-year-old capybara showed some 'unusual' vascular smooth muscle described as 'granular', which suggested a remodeling process in the artery at this animal age, when ICA regression occurs [Islam et al, 2004].…”

“…At maturation, at around 1 year of age, ICA regression can be observed in this species [Reckziegel et al, 2001], suggesting that from this stage the main blood supply to the capybara brain is via the BA of the vertebrobasilar system. Morphological features suggesting BA remodeling in capybara during ICA regression have been described [Islam et al, 2004;Steele et al, 2006].…”