Interaction of adenosine and naloxone on regional cerebral blood flow in morphine-dependent rats.
The present research aimed at investigating the opioid-adenosine interaction on regional cerebral blood flow (rCBF). Therefore rCBF in the sensory cortex of morphine-naive and -dependent rats was measured using the laser-Doppler flowmetry technique. The results showed that adenosine (10(-5), 10(-4), 10(-3) M) significantly increased rCBF in morphine-dependent rats (MDR) (P < 0.01). This effect was inhibited by theophylline (5 x 10(-5) M). Also systemic naloxone (0.5, 1.5 and 3 mg/kg, s.c.) significantly increased rCBF in MDR and it was accompanied by elevated blood pressure and heart rate. Local adenosine (10(-4) M) significantly augmented naloxone (0.5 mg/kg)-induced increase in rCBF of MDR but had no significant effect on naloxone's (1.5 and 3 mg/kg) increasing effect on rCBF. Theophylline also has no effect on naloxone increasing effect on rCBF. These data suggest that adenosine receptors responsiveness increase in sensory cortex of MDR. Naloxone also highly increased rCBF of MDR that probably not interfere with adenosine receptors. Also, it seems that adenosine acts as a modulator in rCBF regulation of morphine-dependent and morphine withdrawal rats.
Khorasani
Mahdi Zahedi
MZ
Physiological Research Centre, Semnan University of Medical Sciences, P.O. Box 35195-163, Semnan, Iran.
Hajizadeh
Sohrab
S
Fathollahi
Yaghoub
Y
Semnanian
Saeed
S
D000241:Adenosine / Q000494:pharmacology*; D000700:Analgesics / Q000494:pharmacology*; D000704:Analysis of Variance; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002540:Cerebral Cortex / Q000098:blood supply*; D002560:Cerebrovascular Circulation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004347:Drug Interactions; D017078:Laser-Doppler Flowmetry / Q000379:methods; D008297:Male; D009021:Morphine Dependence / Q000188:drug therapy / Q000503:physiopathology*; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects
D000700:Analgesics; D009292:Narcotic Antagonists; D009270:Naloxone; D000241:Adenosine