CHANGES OF DOPAMINE-SENSITIVE CYCLIC AMP-GENERATING SYSTEM IN THE RAT HIPPOCAMPUS AS A FUNCTION OF AGE

The dopamine (DA) D1 and D2 receptors coupled to the 3′,5′-cyclic adenosine monophosphate (cAMP)-generating system were studied in membrane particles of the dorsal hippocampus in 3 (considered to be young), 12 (considered to be adult) and 24 (considered to be old) month male Sprague-Dawley rats. Activation of D1 receptors with DA, apomorphine or SKF 82526 enhanced accumulation of cAMP in the hippocampus of rats of the three age groups examined. This stimulatory effect was significantly reduced in adult rats. No further changes were noticeable in old animals. D2 receptors negatively coupled to cAMP generation were demonstrated by incubating hippocampus membrane particles with SCH 23390 plus DA or with D2 receptor agonists quinpirole or bromocriptine. The D2 inhibitory effect on cAMP generation was unchanged in the three age groups. No difference was detectable between young, adult and old rats in the activation of cAMP production by forskolin. © 1990.