Perivascular injury leads to a reduction in vascular reactivity of the collared and to an enhancement on contralateral carotid artery of rats.

BACKGROUND: The first response to perivascular injury is observed in the adventitial layer. The purpose of this study was to determine the time course of vascular reactivity alterations after collar injury in rats. We also analyzed the relation between adventitial layer injury and vascular responsiveness to vasoconstrictor agents. METHODS: Wistar rats had a silicone collar positioned around the carotid artery. The ipsilateral and contralateral arteries were morphologically analyzed 4, 7, 14 and 28 days after injury, and cumulative concentration-response curves to phenylephrine (Phe), angiotensin II (Ang II) and KCl were obtained for arteries isolated from collared and sham-operated groups. RESULTS: Inflammatory cells and fibroblasts were observed in the adventitial layer of collared arteries 4, 7, 14 and 28 days after injury. Intimal thickening was observed in collared arteries only 14 and 28 days after perivascular injury. A decrease in maximum effect values (Emax) for Phe, Ang II and KCl was observed in the collared artery when compared with the contralateral artery at all times after injury, whereas an increase in vascular responsiveness was observed in the contralateral artery 4 days after injury. CONCLUSIONS: The impairment of the contractile response preceded the intimal thickening. The compromise of vascular reactivity coincided with the presence of inflammatory cells and angiogenesis in the adventitial layer. The enhancement of the efficacy and potency of Ang II and Phe in collared-contralateral arteries 4 days after collar placement may be related to a receptor-mediated compensatory mechanism stimulated by the collar injury.

Fine structure of the sensory nerve endings of the lower lip mucosa of Cebus apella monkey

The morphology of the sensory nerve endings of lower lip mucosa was studied using transmission electron microscopy. The sensory nerve endings are constituted by several thin terminal axons ranging from O.25 to 1.5 mum, and each one is somrrounded by cytoplasmic processes of lamellar cells. These lamellae measure approximately 0.l5mum in width, and contain rough endoplasmic reticulum, mitochondria, microfilaments, and caveolae. Between the lamellae and the terminal axons and also the adjacent lamella are noted desmosome-type junctions. The terminal axons contain numerous mitochondria and clear vesicles measuring from 30 to 5Onm in diameter. The basal lamina of lamellar processes is generally extense appearing as several electron dense lines, and the interlamellar space is characterized by an amorphous substance and some fine collagen fibrils.