Brain monoamine levels in the cow during oestrus and metoestrus.

Norepinephrine, dopamine, and serotonin concentrations in the hypothalamus and stalk-median eminence were estimated in nine Hereford heifers at the onset of oestrus or 48 hr later. Significant differences in levels of monoamines at these stages of the oestrous cycle were not evident. Norepinephrine levels were similar in the hypothalamus and the stalk-median eminence, but dopamine and serotonin concentrations were significantly higher in the stalk-median eminence.