Studies of leptomeningeal collateral circulation in Macacus rhesus

Abstract

In previous experiments on dogs (Symon, 1960), it was shown that, within a few minutes of occlusion of a major cerebral vessel, free flow of blood occurred within the area of supply of the occluded vessel, borne via leptomeningeal anastomoses from the vascular fields of adjacent vessels. Since it has been established anatomically (Vander Eecken, 1959) that the number and size of collateral vessels within the pial circulation decreases with increasing convolution of the cortex in higher animals, it became of interest to find out whether such prompt collateral flow could be demonstrated in these animals as well. Similar experiments were therefore carried out in the primate Macacus rhesus. METHODSEighteen macaque monkeys weighing between 3 and 5 kg were used. They were anaesthetized with intravenous thiopentone sodium in an initial dose of 25 mg/kg, supplemented at intervals by intravenous doses of 25 mg as required. An endotracheal tube was passed to facilitate maintenance of a clear airway throughout. The blood pressure was continuously recorded from the cannulated femoral artery.Dissection of the carotid sinus. The area of the right carotid sinus was exposed, and the carotid-sinus nerve divided. No ligations of vessels were necessary, since in the macaque, unlike the dog, the main route for blood from the area of the carotid sinus to the cerebral cortex is via the internal carotid artery, and anastomoses between intra-and extra-cranial vessels are small and functionally unimportant.A polythene cannula with dead space 0 1 ml. was introduced into the lingual artery and threaded for a few millimetres down the external carotid artery, so that its tip lay in the carotid sinus, care being taken not to occlude the origin of the internal carotid artery. Injections of 0-5 ml. of labelled erythrocyte suspension were made through this cannula from a tuberculin syringe. These injections were made as rapidly as possible. After each injection the cannula was flushed out and filled with a solution of heparin (500 u./ml.). In some experiments this dissection was performed on both sides.Exposure and occlusion of the vertebral arteries in the neck. A curved transverse incision was made half an inch (12 mm) above the sternoclavicular joints, extending for 2-5 cm on either side of the mid line. Both sternomastoid muscles were divided and the carotid sheaths gently retracted medially. The origin of scalenus anterior was defined, behind the carotid sheath, arising from the transverse processes of the cervical vertebrae. The vertebral artery was found in the interval between the longus cervicis muscle on the vertebral bodies and

A comparative study of middle cerebral pressure in dogs and macaques

“…These anastomoses have been demonstrated anatomically many times (Heubner, 1872;Beevor, 1907 ;Vander Eecken & Adams, 1953) and function within a few moments of vascular occlusion in both the dog and macaque (Symon, 1960(Symon, , 1961. In the present experiments, both species showed an immediate fall in arterial pressure within the middle cerebral field on middle cerebral occlusion to similar levels, between 18 and 30 mm Hg, but in dogs there was frequently an elevation of this pressure within 2 or 3 min, and several dogs showed a restoration of pulse distal to the occlusion.…”

“…In the monkeys, anaesthesia was induced with thiopentone 20 mg/kg and maintained with chloralose 60 mg/kg. Previous experience (Symon, 1961) has shown that prolonged thiopentone anaesthesia in the monkey is unsatisfactory.…”

“…The carotid and vertebral vessels were exposed in the neck as described previously (Symon, 1961). Occlusion of a carotid artery was preceded by section of the carotid sinus nerve to diiminish changes in arterial blood pressure.…”

“…Witbin the skull, other collateral channels in the leptomeninges have been shown to function within a few minutes of occlusion of a major cerebral vessel (Petersen & Evans, 1937; Symon, 1960Symon, , 1961. They have been found responsible for the restoration of blood flow within the territory 29 Physiol.…”

The Distribution and Density of Reduced Cerebral Blood Flow Following Acute Middle Cerebral Artery Occlusion: An Experimental Study by the Technique of Hydrogen Clearance in Baboons

“…The variability of the clinical deficit produced by middle cerebral occlusion is well recognized, and it is probable that the two factors most involved in this variability are the variation in collateral potential from animal to animal -a relatively minor factor -and, more important, the variation from one experimental model to another in the degree of involvement of the perforating branches, 7 occlusion of which produces a dense ischemic lesion in the basal ganglia and internal capsule. Perfusion studies have demonstrated that the area of ischemia produced by middle cerebral occlusion in the monkey 8 or dog 9 is quite similar to that produced by acute middle cerebral obstruction, thrombosis, or embolization in man. The areas most densely involved are the Sylvian opercula and, provided the perforating arteries have been occluded by insult, the putamen and lentiform nucleus in the basal ganglia.…”