360 Effect of Hypermagnesemia on Neonatal Neuromuscular Function (Nmf)

Abstract

Effect of hypermagnesemia on feeding was studied in 3 groups.Group A -hypermagnesemia (HM) infants of magnesium sulfate (MS) treated pre-eclamptic mothers. Cord blood magnesium (CBM) was 4.2 + 0.7 mgldl. Group B -non HM infants (CBM 1.5 + 0.2 mgldl) of untreated pre-eclamptic mothers. Group C -control infants (CBM 1.6 t 0.2 mgldl) of normal non MS treated mothers. Duration and strength of sustained sucking was subjectively evaluated prior to each feeding. Volume of formula consumed at study ages is tabulated as ml per feed + 1 S.D. 4s6 hrs.12 hrs. 24 hrs. 48 hrs.---- Both bur and a v a r i e t y o f~i m m u n o s~i~n u l a n t s have been shown t o i n h i b i t MFO a c t i v i t y . We wished t o determine whether the a c t i o n o f Cp i s mediated by GH and, i f not, whether there i s evidence o f a common mechanism. Cp i n a single dose o f 20 mg/kg resulted i n increased r ( r a t ) GH l e v e l s i n trunk blood 96 hours l a t e r (96t27 vs 24*2 ng/ml; p<0.05) and i n p i t u i t a r y glands (136k16 vs 91f.8 mcg/mg ; p<0.05).Frequent sampling studies showed t h a t spontaneous rGH secretion was s i g n i f i c a n t l y greater 24 h r a f t e r Cp. However, hypophysectomized male and female r a t s s t i l l responded t o Cp w i t h s i g n i f i c a n t decreases i n aminopyrine-Ndemethylase and a n i l i n e hydroxylase a c t i v i t i e s i n l i v e r microsomes and w i t h a f a l l i n cytochrome P450 content. I n i n t a c t animals, rGH o f P~ychology, A1 bany. Group A-hypermagnesemic (HM) infants of magnesium sulfate (MS)Studies on the r a t indicate that, as suggested by human case treated preeclamptic mothers. Cord blood M~*(CBM) was 4.25.7reports, e a r l y propranolol exposure r e s u l t s i n a growth d e f i c i t . mg/dl. Group B-control infants of normal non MS treated mothersBrain weight was s i g n i f i c a n t l y smaller i n suckling r a t s given (CBM 1.59.2 mg/dl). Tension(t) generated by thenar muscle cond a i l y propranolol 50 mg/kg by gavage s t a r t i n g on day 4. Mean centration in response to ulnar nerve stimulation was measured by brain wei h t was 1.36*0.02g vs 1.45t0.01g i n vehicle treated recording initial train of 4 (T4=4 stimuli )I sec. apart), tetany controls Qp<O.Ol). To determine whether there was a functional produced by 50 and 100 HZ stimuli, and post-tetanic T4. Results d e f i c i t accompanying the anatomical one, behavioural studies were are expressed as %fade ( [(+-initial-tf inal) Itinitial] x 100).carried out when the r a t s were 50-60 days o f age. Propranolol Initial ~4 50 HZ Tet. 100 Hz Tet. Post-Tet.T4 exposed animals required s i g n i f i c a n t l y more t r i a l s t o reach Group(n) A (15) B (17) A (15) B (15) A (14) B (14) A (15)