Arterial Vascularization of the Base of the Brain in Galea (Galea spixii)

Abstract

Background: Galea (Galea spixii) are rodents which are especially distributed in the northeastern region of Brazil, and have economic importance as their meat is used as a source of protein by the regional population. Currently, they have received attention from researchers in studies involving their morphology. Thus, seeking to contribute information that supports their sanitary management in addition to the lack of literature on their nervous system, our objective was to describe the arterial vascularization of the base of the brain in this species, in order to identify the arterial pattern and arterial circuit behavior, as well as possible variations in these vessels.Materials, Methods & Results: Brains were obtained from 20 animals (10 males and 10 females) aged between 11 and 12 months, obtained from the Wild Animal Multiplication Center (CEMAS) of the Federal Rural Semi-Arid University (UFERSA), under the approval of CEUA/UFERSA (case number 23.091.000653/2014-26 and opinion number 15/2014), euthanized according to anesthetic protocol recommended for rodents (resolution number 714/2002 of the CFMV/ UFERSA) and preserved frozen in a freezer for an average period of 30 days. The animals were thawed and a longitudinal incision was performed in the thoracic region to allow exposure of the aortic arch. Next, they were cannulated in the cranial direction and injected with Noprene Latex “650” stained with water-based white or red pigment. The animals were subsequently fixed in 3.7% aqueous formaldehyde solution for 48 h, and soon after the brain skull cap was dissected and removed, which was then analyzed, photographed and sketched. Of the 20 animals evaluated, 100% presented vertebrobasilar system responsible for encephalic irrigation of the rostral and caudal regions, and anastomosis of the left internal carotid artery was found in only one case (female) (5%), irrigating the rostral region of the encephalon together with the vertebro-basilar system. In the most frequently found arrangement, the unpaired main arteries present at the base of the brain included: ventral spinal, basilar, medial branch of the rostrais cerebral arteries, medial rostral inter-hemisphere; and the pairs: vertebral, cerebellar caudal, middle cerebellar, trigeminal, rostral cerebellar, rostral tectal, caudal cerebral, pituitary, internal ophthalmic, middle cerebral, rostral cerebral, lateral olfactory bulb and internal ethmoid. Arterial circuit formation was observed as being geometrically similar to a complete, closed and elongated hexagon in the caudal-rostral direction, bypassing the mammillary body, the cinereous tuft and the optic chiasm.Discussion: The study of the nervous system, especially on identification of the arteries responsible for supplying the brain is relevant, especially when it comes to a wild species such as in galea considering that little is known about their morphology, and also because it can be used as a model in clinical and surgical studies related to the nervous system. Based on the analyzed animals, we conclude that the arterial vascularization of the base of the brain in galea is type III, similar to the findings in other species of rodents such as in otters and porcupines; and differing from those described for agoutis and mice-moles. The arterial circuit of galea is complete and closed like those described for the agouti and the European beaver, yet differing from that observed for otters and chinchillas which have an open circuit.