Comparsion between electrical lesion and stimulation of nucleus tractus soloitarii on baroreflex sensitivity in morphine addicted rats

Introduction: There is considerable evidence for an interaction between opiate
systems and cardiovascular regulatory area in the central nervous system. The
endogenous opiate systems are known to depress the baroreflex sensitivity in
morphine dependent persons. Nucleus Tractus Soloitarii (NTS) is the principal
site of termination of baroreceptor afferent neurons,. We conducted this study to
determine the role of electrical stimulation in Nucleus Tractus Soloitarii on
baroreflex sensitivity in morphine – addicted rats.
Methods: In this experimental study, male Wistar rats were addicted during a
scheduled 10 day period with morphine sulphate (i.p) and anesthetized by
Urethane (150mg/100gr body weight i.v) then cannulasted with PE50 tubs filled
with heparin / saline (200u/ml) in femoral artery and vein for recording mean
arterial pressure (MAP) and heart rate (HR). The electrodes were induced in
NTS, according to paxinous atlas in streotaxic instruments for applying electrical
lesion and stimulation. Phenylepherine was used as a vasoconstrictor to induce
acute arterial pressure. Baroreflex sensitivity was evaluated (HR/MAP) before
and after electrical stimulation application in NTS. The control group received
saline instead of morphine.
Results: The results shows that baroreflex sensitivity has been decreased in
morphine addicted rats compared with control. There are no significant changes
in MAP and HR after electrical stimulation application in NTS in both morphine
and control groups, but MAP and HR were increased after electrical lesion in
both groups. Baroreflex sensitivity increased after application of electrical lesion
in control (P<0.05) and morphine receiving groups (P<0.05).
Conclusion: It is suggested that application of electrical stimulation in NTS can
modulate neurotransmission in central nervous system such as GAB Aergic
function, therefore this modulation may prevent some abnormality in
cardiovascular area in addicted rats.