The effects of ether stress and betamethasone treatment on the concentrations of noradrenaline and dopamine in various regions of the rat brain.

1. The effects of ether stress on noradrenaline (NA) and dopamine levels in different regions of the rat brain were studied. 2. Exposure to ether vapour (90 s) caused a significant decrease in the concentration of hypothalamic NA but had no effect on catecholamine (CA) concentrations in the other regions studied. 3. Treatment with betamethasone alone (20 microgram/ml) given in the drinking water for 24 h, had no effect on CA levels in the cerebral cortex, midbrain or hypothalamus. However, pretreatment with this dose of steroid prevented the decreases in hypothalamic NA which were normally seen after ether stress and also induced significant increases in the concentration of midbrain NA. 4. The data provide further support for the involvement of NA in the regulation stress-induced corticotrophin (ACTH) release and indicate that centres other than the hypothalamus may be involved in mediating the inhibitory action of betamethasone on the response to ether stress.