COMPARATIVE-STUDY OF NORMOTENSIVE AND HYPERTENSIVE NITRIC-OXIDE SYNTHASE INHIBITORS ON MORPHINE-WITHDRAWAL SYNDROME IN RATS

The effects of the normotensive, mainly centrally active nitric oxide synthase (NOS) inhibitor 7-nitro indazole and the hypertensive drug N- G-nitro-L-arginine, which blocks both the endothelial and the central NOS, have been examined on naloxone-precipitated withdrawal in morphin e-dependent rats. Both drugs attenuated the same withdrawal signs (tee th-chattering, penile licking, diarrhoea, chewing, wet-dog shakes, gro oming), while other signs remained unaffected (rearing, jumping, ptosi s, rhinorrhoea, irritability on touch). These findings indicate that m ainly central (but not endothelial) nitric oxide is involved in the ex pression of some opioid withdrawal symptoms.