A New Approach to the Study of Latissimus Dorsi Muscle Vasoreactivity in Rats

In this paper we describe a new approach to the study of changes in latissimus dorsi (LD) muscle microcirculation in rats. The experiments were carried out under anesthesia in normal male Wistar rats (C, n = 6) and in diabetes-induced rats (D, streptozotocin, 50 mg/kg, i.v., n = 6). The left LD muscle was exposed in order to preserve the proximal tendon with its thoracodorsal nerve and artery. The animal was kept in lateral decubitus over a heating board attached to the mechanical stage of the intravital microscope. The ventral surface of the muscle was exposed over a transparent plate and fixing. The image of the LD vascularization was transferred to the camera system, which was connected to a microcomputer equipped with software (KS-300, Kontron Elektronik, Munich, Germany) for image storage. The vasoreactivity of LD was analyzed by changes in arteriole diameter after topically administered noradrenaline (0.3 microg/ml) and acetylcholine (300 microg/ml). The microscopic image provided by the described optical setup permitted clear resolution of capillary vessels and a stable preparation over a period of 3-4 h. D rats showed increased vasodilatation (29 +/- 2% vs. 18 +/- 2.6% in C) and similar vasoconstriction (25.5 +/- 3% vs. 27.5 +/- 3.3% in C) as compared to C rats. The method described in this paper is suitable for the study of changes in responsiveness of LD arterioles, vessels which represent the major site of vascular resistance and are most actively involved in the control of tissue perfusion.