Histamine and histamine-N-methyltransferase in the goat brain.

Histamine concentrations and histamine-N-methyltransferase (HMT) (EC 2.1.1.8) activities were assayed in the goat brain, since this animal has been used for the purpose of assessing the physiological role of histamine in the central nervous system. The highest histamine concentrations were found in the hypothalamus (616 +/- 88 ng/g), 'thalamus' (244 +/- 41), preoptic area (242 +/- 95) and 'area postrema' (170 +/- 52), and are three to tenfold higher than the average concentration in the whole brain (76 +/- 9). The pineal body and choroid plexus contained very high concentrations of histamine (5800 and 5400 ng/g, respectively) and the pituitary gland had about the same as the hypothalamus (564 +/- 248 ng/g). There was little variation in the HMT activity in various parts of the brain and in the glands. In the cerebrospinal fluid both histamine concentration and HMT activity were very low, some increase occurred post mortem, but not within 20 minutes of death. The results indicate that the distribution of histamine and that of HMT in the goat brain are fairly similar to those in other mammalian brains, supporting the assumption that histamine might have a physiological function in the brain, especially in the hypothalamus.