STRAIN DIFFERENCES IN THE INHIBITION BY HEMICHOLINIUM‐3 OF THE PRESSOR RESPONSE TO INTRAVENTRICULAR INJECTION OF NEOSTIGMINE IN RATS

The pressor response to intracerebroventricular (i.c.v.) injections of neostigmine was examined in three groups of Sprague-Dawley rats (MFS, CS and CFE) obtained from different breeders and in Long-Evans rats (MLE) obtained from one of the same breeders. All rats responded with a rise in blood pressure to i.c.v. injection of neostigmine, although the CFE strain was 6-fold less sensitive to the drug than were the other strains.Prior i.c.v. injection of hemicholinium-3 (HC-3; 0.4 mug) reduced by more than 50% the pressor response in the two strains obtained from the same breeder (MFS and MLE) and caused an 1 1% reduction in the CS strain. In contrast, the pressor response in CFE rats was not affected by as much as 40mug of HC-3, although this dose decreased the response to neostigmine by 47-66% in the other three strains.