Effect of ventral noradrenergic bundle transection and locus coeruleus lesions on urinary 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) excretion in the rat

Urinary 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG) excretion was determined in rats after central noradrenergic pathway interruption by ventral bundle transection or by locus coeruleus (LC) lesions. The transection prevented an increase in urinary MHPG that occurred in sham-operated animals, an effect that was presumed to be due to loss of cerebrospinal fluid (CSF). Electrolytic lesioning of the LC, which was not attended by loss of CSF, had no effect on baseline MHPG excretion but diminished the response to subsequent administration of the α-adrenergic blocking agent, phenoxybenzamine (PBZ). Since the contribution of brain MHPG to total urinary MHPG is small, the observed effects of these procedures are most likely due to disrupted central regulation of peripheral sympathetic nerve activity.