Central cardiovascular effects of 6-hydroxydopamine

Effects of 6-hydroxydopamine (6-OHDA) on the vasomotor loci of medulla oblongata, hypothalamus and spinal cord have been investigated in anaesthetized (chloralosed) cats. Intracerebroventricular (i.c.v.) and intrathecal (i.t.) administration of 6-OHDA, 0.5–2.0 mg, inhibited reflex, as well as direct, excitability of vasomotor loci. The blood pressure and the heart rate were reduced for a prolonged period. Central tyramine response was blocked while peripheral noradrenaline response remained unaffected. The adrenergic neurones appear to have an excitatory function in central cardiovascular regulation.