The effects of dopamine (DA), 5-hydroxydopamine (5-OH-DA), and 6-hydroxydopamine (6-OH-DA) administered into the cerebro spinal fluid on choline acetylase (ChAc) activity, endogenous levels of norepinephrine (NE), dopamine (DA) and serotonin (5-HT) in the rat brain were studied. In vitro tests, showed that dopamine and 6-OH-DA at concentrations of 10-2 to 10-4 M significantly decreased ChAc activity. Chronic studies showed that both DA and 5-OH-DA activated ChAc whereas 6-OH-DA caused an initial decrease in the enzyme activity followed rapid recovery after 4 days. DA treatment increased the levels of NE and DA in the brain whereas 5-HT level was not significantly changed. 5-OH-DA treatment markedly reduced the levels of NE, increased the levels of 5-HT but did not significantly affect the DA level. 6-OH-DA treatment caused a significant reduction in NE, a small decrease in DA level, and no significant change in the level of 5-HT. The data showed interaction between the various monoamines and their effects on ChAc activity. These findings support the concept suggested in previous studies on the control of eating behaviour, of an adrenergic-cholinergic interaction in the central nervous system.
- Adrenergic-cholinergic interaction
- Brain monoamines Brain choline acetylase