Background & Aims: Frequent administration of morphine leads to increase in motor activity, motivational properties, and other responses related to this kind of drugs.  It has been reported that the impact of morphine on seizure is dose dependent. The aim of this study was to study the impact of chronic exposure to morphine on pentylenetetrazol-induced seizure in rats.

Materials & Methods: Neonate rats (n=40) were randomly chosen and divided into two groups. On postnatal days 8-14 one group received daily morphine and the other group received saline.  On postnatal days 25 and 32, all rats injected intraperitoneally with 60 mg/kg pentylenetetrazol and seizure behaviors were monitored.

Results: Number of grooming decreased in morphine groups compared to saline animals (p<0.05). Duration of grooming decreased in 32-day-old morphine treated rats compared to their saline group (p<0.01). Latency to widening rear limbs decreased in 25-day-old morphine treated rats compared to saline group while it increased in 32-day-old rats (p<0.05). Probability of incidence of tonic-clonic seizure increased 2.4 times in 25-day-old morphine treated rats compared to saline group but it changed in opposite direction in 32-day-old rats.

Conclusion: These results suggest that chronic exposure to morphine during neonatal period induces age-dependent alterations in the susceptibility to pentylenetetrazol-induced seizures. It is likely that exposure to morphine leads to alterations in developing of brain systems such as glutamate which in turn change the susceptibility to seizure. 

SOURCE: URMIA MED J 2012: 23(3): 347 ISSN: 1027-3727