EFFECTS OF INTRASEPTAL INJECTION OF 192-IGG-SAPORIN IN MATURE AND AGED LONG-EVANS RATS

In this study, the effects intraseptal injections of the selective cho linergic immunotoxin, 192-IgG-saporin, were investigated in mature (6- month-old) and aged (24-26-month-old) male Long-Evans rats. Ten days f ollowing intraseptal injection of either 192-IgG-saporin or saline, te sting began in a battery of behavioral tests modulated by the septohip pocampal system including two versions of the Morris water maze (i.e. submerged platform task, and 2-platform spatial discrimination), inhib itory avoidance, and pre-pulse inhibition of acoustic startle. In both mature and aged rats, intraseptal injection of 192-IgG-saporin select ively reduced ChAT activity in the hippocampus and posterior cingulate cortex, without affecting ChAT activity of amygdala or parietal corte x. In general, in all of the behavioral tests analyzed, intraseptal 19 2-IgG-saporin treatment had no effect in mature animals. Age-related d eficits were observed in the spatial memory tasks, however this impair ment was largely a function of the poor performance of aged rats treat ed with the toxin. In addition, an increase in the response to an acou stic startle was found in aged rats treated with 192-IgG saporin. Thus , although intraseptal injection of 192-IgG-saporin produced similar r eductions of ChAT activity, performance of mature and aged rats in tas ks believed to be modulated by the septohippocampal pathway tended to be differentially affected in mature and aged rats.