Changes in posterior hypothalamic self-stimulation following experimental cerebral infarction in the rat.

Bipolar stimulating electrodes were placed bilaterally in the posterior hypothalamus of male Sprague-Dawley rats following which the Ss were shaped for intracranial self-stimulation (ICSS). When ICSS rates were stable for 1 wk, the right middle cerebral artery was ligated. During the 25-day postinfarction period, the rate of ICSS at specified current values was compared with preoperative rates. At 2 days after operation, there was a 33% decrease in the maximum frequency of ipsilateral ICSS. By 8 days after experimental stroke, there was a 16% increase in the maximal rate of ICSS above the preoperative values, and the rate returned to control levels by 20 days after surgery. The minimum current necessary to elicit the maximal rate of response also changed in a biphasic manner (i.e., minimum required current was greater than preoperative control levels until 8 days after operation but then dropped below control level until 20 days postoperative). There were no changes in the current or rate of response in the contralateral electrode. Results are discussed in relation to what may be the underlying neurophysiological changes causing these biphasic alterations in ICSS. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)