Chronic stress increases the binding of the A1 adenosine receptor agonist, [3H]cyclohexyladenosine, to rat hypothalamus.

We previously reported an increase in the binding of [3H]cyclohexyladenosine ([3H]CHA) to brain membranes from the hypothalamus of rats sacrificed following three days of chronic stress in an around-the-clock intermittent footshock avoidance/escape paradigm ("sustained performance" stress). Here we report stress-induced increases in [3H]CHA binding to hypothalamic membranes from rats stressed for 14 days in that escape/avoidance paradigm, in rats exposed to repeated restraint (3 hr/day for 10 days) and in rats exposed to four days of "activity-stress." Data from saturation binding experiments indicate that this up-regulation was due to an increase in the apparent number of [3H]CHA binding sites without change in affinity for [3H]CHA. Neither restraint for one three-hr period nor one 15-min exposure to intermittent footshock resulted in significant changes in [3H]CHA binding to hypothalamic membranes. Our present data demonstrate small but consistent increases in the number of [3H]CHA binding sites in hypothalamic membranes from rats stressed in several different chronic stress models but no change by acute stress.