NEUROPEPTIDE-Y PLASMA-LEVELS AND SERUM DOPAMINE-BETA-HYDROXYLASE ACTIVITY IN MS PATIENTS WITH AND WITHOUT ABNORMAL CARDIOVASCULAR REFLEXES

An impairment in the autonomic function has been demonstrated in patie nts with multiple sclerosis (MS) using electrophysiological, pupillary and biochemical tests. Particularly evident were alterations in the c ardiovascular reflexes, cutaneous sympathetic response and lymphomonoc yte adrenergic binding. Electrophysiological and biochemical findings in MS patients have only occasionally been compared. Among the periphe ral markers of the autonomic system, Neuropeptide Y (NPY) and dopamine -beta-hydroxylase (DBH) have been singled out as reliable indices of s ympathetic function. The former is a peptide with a strong vasoconstri ctive action, which is released from adrenergic endings together with noradrenaline following sympathetic activation. The latter is the enzy me which catalyses the conversion of dopamine to norepinephrine. It is located both in sympathetic endings and the chromaffin granules of ad renal medulla. To verify a failure in autonomic function in the course of MS, a battery of cardiovascular tests (assessing sympathetic and p arasympathetic functions) was performed on 25 MS patients. The results were compared with a group of 20 age- and sex-matched control individ uals. The plasma levels of NPY and the serum DBH activity were also de termined in both groups. 52% of patients showed an impairment in sympa thetic function in one or more tests (substained handgrip, postural hy potension, cold face test). 48% of the patients had abnormal values in deep breathing test, indicating a failure of the parasympathetic func tion. 44% of patients showed also a paroxysmal tachycardia after cold face test, indicating an abnormal function of the vagal-cardiac and sy mpathetic-vascular smooth muscle pathways of the trigeminal nerve. The plasma NPY and serum DBH activity were significantly reduced in MS pa tients compared to the control group (p < 0.02 and p < 0.002, respecti vely). The levels were even lower in patients with the progressive for m and in those with an abnormality of the sympathetic function reveale d by cardiovascular tests. These findings indicate that the contempora ry use of electrophysiological and biochemical tests would give a more comprehensive picture of the sympathetic function in MS patients.