Effect of administration of 3-acetylpyridine followed by niacinamide injection on survival, extent of the inferior olivary complex lesion, and response to harmaline in the young rat

In the 15 day-old DA/HAN strained rat, i.p. injection of 3-acetylpyridine (3-AP) 50, 65 or 95 mg · kg −1 was followed 2 to 4 hours later by administration of niacinamide (300 mg · kg −1). The percentage of survival and the extent of the inferior olivary complex (IOC) lesion, determined histologically, were correlated with both the dose of 3-AP administered and the time delay between 3-AP and niacinamide injections. Moreover, the tremor elicited by harmaline was also correlated with the extent of the IOC lesion. The results show that it is more advantageous to administer 95 mg · kg −1 3-AP and to delay niacinamide injection by 2h30 or less to get the higher percentage of survival (about 90%) and a reasonably high percentage of totally IOC lesioned rats (more than 30%). They also demonstrate that the harmaline test is not sufficient to acutely judge of the extent of the IOC lesion and that, in all cases, histological controls have to be done. The results are discussed in terms of interrelationships of the variable studied.