Effects of Paragigantocellularis Lateralis (LPGi) Nucleus Electrical Lesion on Withdrawal Syndrome in Morphine Dependent Male Rats

Nucleus paragigantocellularis lateralis (LPGi) involves in several physiological functions such as cardiovascular regulation, sexual behavior and pain. There is little evidence about its role on opiate withdrawal. In this research the effect of LPGi electrical lesion on withdrawal syndrome in morphine-dependent rats was studied. N-MRI rats were divided into three groups: Control, Sham and Lesion group. Animals were anaesthetized using ketamine (110 mg/kg) and rampone (3 mg/kg) mixture injection (i.p). Stainless steel electrodes were placed in LPGi (AP=11.8, L=±1.6, DP=10.5) bilaterally. LPGi was lesioned using electrical current (1 mA, DC) for 6 seconds. After 10 days recovery period animals were addicted by morphine injection two times a day for 4 days (every day 25, 30, 35, 40 mg/kg respectively). In the fifth day 40mg/kg morphine have been injected to animals and after 30 min withdrawal syndrome was induced by naloxane injection (4 mg/kg i.p) and evaluated withdrawal sign (rearing, ptosis of eye lid, teeth chattering, grooming, wet dog shakes, paw tremor, body tremor, number of ejaculation, defecating, jumping). Our results showed that LPGi lesion only can decreased ejuculation, paw tremor and wet dog shakes significantly (p<0.02) but LPGi lesion did not affect other withdrawal signs. Our data showed that LPGi altered only ejaculation, paw tremor and wet dog shakes. It seems that LPGi have critical role in those sings and other withdrawal sing related to other nucleus such as PGi and LC.