EFFECTS OF CENTRAL SEROTONIN NERVE LESIONS ON BLOOD PRESSURE IN NORMOTENSIVE AND HYPERTENSIVE RATS

1 Separate ascending and descending pathways of serotonin (5‐hy‐droxytryptamine, 5‐HT) nerves in the rat central nervous system have been selectively lesioned by Idealized intracerebral administration of 5,7‐dihydroxytryptamine (5,7‐DHT) after pretreatment with desipramine (DMI). 2 Bilateral injections of 5,7‐DHT into the medial forebrain bundle or the cervical spinal cord caused extensive losses of 5‐HT and tryptophan hydroxylase in the anterior hypothalamus and thoracic spinal cord, respectively, without affecting noradrenaline (NA) levels. 3 The hypothalamic lesions caused only a slight, transient reduction of systolic blood pressure in normotensive rats. 4 A more pronounced and sustained hypotension occurred in normotensive rats but not in hypertensive rats after the spinal lesions.