Evidence for lower sympathetic nerve activity in young adults with low birth weight.
OBJECTIVE
A dysfunction of the sympathetic nervous system may contribute to the development of hypertension and obesity in subjects with low birth weight (LBW). The present study examines resting sympathetic nerve traffic and its baroreflex modulation to the muscle vascular bed in healthy LBW subjects.


METHODS
Case-control studies of 13 healthy LBW subjects (< 2500 g at term) aged 20-30 years and 13 normal birth weight subjects (NBW; 3200-3700 g) closely matched for age, gender and body mass index.


METHODS
Muscle sympathetic nerve activity (MSNA) recordings from the superficial peroneal nerve, blood pressure and heart rate were obtained at rest, during an inspiratory apnoea and a cold pressor test. Baroreflex function was evaluated by short-term infusion of nitroprusside and phenylephrine, respectively, in nine subjects of each group.


RESULTS
During resting conditions burst frequency was significantly lower in LBW subjects (LBW: 24.7 +/- 2.4; NBW: 34.4 +/- 2.1 bursts/min, P < 0.05). When normalized for the different baseline values, baroreflex-mediated changes in MSNA were similar in both groups. Maximal MSNA levels in response to inspiratory apnoea and the cold pressor test did not differ between the groups. Blood pressure and heart rate were similar in LBW and NBW subjects both at rest and during sympatho-excitatory manoeuvres.


CONCLUSIONS
Subjects born too small for their gestational age show a significantly lower sympathetic nerve activity under baseline conditions. Given the different baseline values, the sympathetic response to haemodynamic alteration is not affected in LBW subjects, and maximal activation during non-haemodynamic sympatho-excitatory manoeuvres is preserved.
Weitz
Gunther
G
Department of Internal Medicine I, Medical University of Lübeck, Lübeck, Germany.
Deckert
Philippe
P
Heindl
Silke
S
Struck
Jan
J
Perras
Boris
B
Dodt
Christoph
C
D000328:Adult; D000450:Aldosterone / Q000097:blood; D000886:Anthropometry; D017704:Baroreflex / Q000502:physiology; D015415:Biomarkers / Q000097:blood; D001724:Birth Weight / Q000502:physiology*; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects / Q000502:physiology; D015992:Body Mass Index; D016022:Case-Control Studies; D003971:Diastole / Q000187:drug effects / Q000502:physiology; D005260:Female; D005858:Germany; D006339:Heart Rate / Q000187:drug effects / Q000502:physiology; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D007320:Inspiratory Capacity / Q000187:drug effects / Q000502:physiology; D007328:Insulin / Q000097:blood; D020738:Leptin / Q000097:blood; D008297:Male; D009599:Nitroprusside / Q000008:administration & dosage; D010543:Peroneal Nerve / Q000187:drug effects / Q000502:physiology; D010656:Phenylephrine / Q000008:administration & dosage; D012016:Reference Values; D012083:Renin / Q000097:blood; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D014662:Vasoconstrictor Agents / Q000008:administration & dosage; D014665:Vasodilator Agents / Q000008:administration & dosage
D015415:Biomarkers; D001786:Blood Glucose; D007328:Insulin; D020738:Leptin; D014662:Vasoconstrictor Agents; D014665:Vasodilator Agents; D009599:Nitroprusside; D010656:Phenylephrine; D000450:Aldosterone; D012083:Renin; D006854:Hydrocortisone