Effect Of Acute Hypotension On Partial Amino Acids Levels In The Medial Vestibular Nuclei Area In Conscious Rats

It has been reported that the activity of vestibular nuclei neuron affects blood pressure and the rhythm of the heart. In contrast, acute hypotension not only affects the spontaneous discharging activity of vestibular nuclei neuron, but also increases the expression of c-Fos protein in vestibular nucleal complex. Our recent study showed that acute hypotension markedly increases the levels of glutamate(Glu) in vestibular nuclei of anaesthetized rats, but decreases that of taurine(Tau). However, it is not known whether acute hypotension can alter the levels of partial amino acids in vestibular nuclei in conscious rats.To determine if amino acids neurotransmitters such as aspartic acid(Asp) Glu glutamine(Gln) glycine(Gly), Tau and alanine(Ala) are involved in the effect of acute hypotension on the excitation of vestibular nuclei, we measured the levels of amino acids in medial vestibular nucleus(MVN) following acute hypotension induced by sodium nitroprusside in conscious rats by the use of the methods of brain microdialysis and high liquid chromatogram analysis. Our data have shown that:1. The levels of excitatory amino acids including Asp and Glu were 3.17±0.48 and 9.36±0.81 pmol/8μl(sample) in MVN of normal conscious rats. However the levels of inhibitory amino acids including Gln Gly Tau and Ala were 22.55±2.91 6.62±0.91 11.76±1.81 and 14.52±1.92 pmol/8μl.2. A 30 % decrease in blood pressure was shown in normal conscious rats received sodium nitroprusside. Acute hypotension increased the levels of Asp Glu Gly and Ala in MVN(P < 0.05). However, the levels of Glu and Tau were decreased significantly by acute hypotention(P< 0.05).