Aging, diazepam exposure and benzodiazepine receptors in rat cortex.

Densities of two benzodiazepine receptor subtypes (BDZ1 and BDZ2) in the frontal cortex of 10- and 27-month-old male Fischer-344 rats were nearly identical. Acute diazepam pretreatment produced a 73% increase in receptor density in the aged rats, mainly in the BDZ2 sites, whereas with the normal adult rat the density increased 42%, primarily due to stimulation of BDZ1 sites. Chronic exposure elicited similar increases of 28-29% in both normal and aged rats but there were subtle differences in the distribution of specific receptors. This study demonstrates a definite effect of age on the response of benzodiazepine receptors to diazepam pretreatment.