Hypothalamic adrenaline synthesis after stimulation of the medial forebrain bundle.

1 The problem of whether locally released noradrenaline can be methylated to adrenaline in the hypothalamus has been investigated. 2 During stimulation of the medial forebrain bundle (MFB) the hypothalamic adrenaline content increased somewhat, but the increase was not statistically significant (13%, mean of 10 experiments). 3 After inhibition of the activity of monoamine oxidase and catechol-O-methyltransferase this increase was much larger (80%, mean of 9 experiments). 4 Adrenalectomy did not prevent the rise in hypothalamic adrenaline after stimulation of the MFB. These results suggest that noradrenaline released during activity of noradrenergic hypothalamic structures may be methylated to adrenaline in the hypothalamus.