Abstract
The objective of this study was to investigate the role of opioid system in PL on the cardiovascular responses of increase mean arterial pressure (MAP) and heart rate (HR) caused by restraint stress (RS). Male Wistar rats (240–280g) were used. Guide cannulae were implanted bilaterally in the PL for drug injection of naloxone (non‐selective antagonist of opioid receptors in the doses of 0.3, 3 and 30nmol/100nL) or vehicle (artificial cerebrospinal fluid, aCSF, 100nL) and a polyethylene catheter was implanted in the femoral artery for mean MAP and HR record, using a computerized acquisition system. 10 minutes before microinjection of drugs or vehicle into the PL, rats were subjected to RS. The RS caused increase in MAP (F35,360=5.2;P< 0.001) and HR (F35,360=7.56; P<0.001), n=8. Naloxone at dose of 3nmol/100nL in PL (n=8) reduced the increase of MAP (F1,808=270; P<0.0001) and tachycardia (F1,924= 329.1, P<0.0001) caused by RS. On the other hand, the doses 0.3nmol/100nL (n=6; MAP: F1,015=75.95; P<0.0001 and HR: F0,3624=0.6565; P=0.0117) and 30nmol/100nL (n=7; MAP: F0,5388=18,01; P<0.0001 and HR: F0,6431=0.3186; P= 0.6578) of naloxone did not cause alterations on MAP and HR caused by RS. The current results suggesting a facilitatory role of PL cortex in aversive responses. Financial Support: CAPES and FAEPA.
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