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.