Experimental model of small deep infarcts involving the hypothalamus in rats - Changes in body temperature and postural reflex

Background and Purpose-Intraluminal middle cerebral artery (MCA) occlusion in rats has been reported to cause hyperthermia assumed to be caused by hyp othalamic damage. To clarify the effects of hypothalamic ischemia on body t emperature and to obtain a model simulating lacunar infarction, we attempte d to produce small infarcts in deep structures (including the hypothalamus) . Methods-A surgical suture was advanced to occlude the origin of the hypotha lamic (HTA) and/or anterior choroidal arteries (AChA) without compromise of the anterior or middle cerebral artery origins. After treatment, rectal te mperature and postural reflex were examined repeatedly for 3 days under non anesthetic conditions. The AChA and HTA and their link with small deep infa rction were then confirmed by TTC, hematoxylin and eosin, and TUNEL stains and by microsurgical dissection after colored silicone perfusion into the c erebral arteries. Results-Advancement of the suture near to but not occluding the MCA origin (0.5 to 1.9 mm proximal) produced small, deep, nonneocortical stokes in 25 of 36 animals without producing MCA ischemic changes. These infarctions mai nly affected the hypothalamus in 13 animals (HTA area: infarct volume 6 +/- 1 mm(3)) and involved both the internal capsule and hypothalamus in 12 ani mals (HTA+AChA area infarct volume 48 +/- 10 mm(3)). Rats with HTA infarcti on alone exhibited persistent hyperthermia for 72 hours; some also had tran sient mild postural abnormality. The AChA+HTA infarct group showed a transi ent elevation of body temperature for 24 hours and definitive postural abno rmality. In the remaining 11 animals, the suture was inadvertently advanced across the MCA origin, producing a large infarct that affected both the ne ocortex (MCA territory) and nonneocortical structures (volume 381 +/- 30 mm (3), n=11), The MCA infarct group displayed a transient hyperthermia and se vere postural abnormality. Conclusions-When properly positioned, the intraluminal suture method permit s selective AChA and/or HTA obstruction without inducing MCA territory isch emia. This model confirms that selective hypothalamic infarction produces s ignificant and sustained temperature regulation abnormalities. The model al so may be useful in investigating the pathophysiology of small, deep, end-v essel infarction.