The effect of intrathecal administration of magnesium sulphate in rats

Abstract

SummarySomatosensory evoked potential, locomotion and vocalisation upon tail pinch in rats was studied in order to determine whether intrathecal magnesium sulphate administration causes spinal anaesthesia. In Wistar rats with indwelling intrathecal catheters, cortical somatosensory evoked potential was recorded following stimulation via electrodes inserted into the hind paw under chloral hydrate anaesthesia before and after intrathecal administration of 10 ml of either magnesium sulphate (12.3% or 24.6%) or lignocaine (4% or 8%). Locomotion and vocalisation after tail pinch were tested following intrathecal administration of the same two drugs in conscious rats. Somatosensory evoked potential amplitude was diminished after administration of lignocaine (p < 0.05) but did not change after magnesium sulphate. Latency of P1 was increased by lignocaine and by magnesium sulphate 12.3% (p < 0.05). Although lower extremity paralysis was observed in both groups, its duration with magnesium sulphate was much longer than with lignocaine. Vocalisation was recognised after magnesium sulphate 12.3%, but was not observed after lignocaine 8% during paralysis (p < 0.05). We believe that magnesium sulphate caused motor paralysis, but not complete analgesia.

Protective effect of prior administration of magnesium on delayed hyperalgesia induced by fentanyl in rats

“…Our study is also in accordance with preclinical studies, which report that intrathecal magnesium suppresses neuropathic pain responses in different rat models, [20][21][22] and delays the development of tolerance when co-FIGURE 2 Effects of ip magnesium pretreatment vs ip saline pretreatment on the short-lasting effect (A) and on the long-lasting effect (B) induced by sc fentanyl 60 µg·kg -1 × 4 as measured by the paw-pressure vocalization test (n = 8 for each group). Mean nociceptive thresholds (± SD) are expressed in grams.…”

The effect of intrathecal magnesium sulphate on nociception in rat acute pain models

“…Magnesium sulphate was dissolved in 0.9% saline, with the final dose always administered in a volume of 10 ml. Rats were divided into five groups and examined for the presence of locomotor dysfunction by an experimenter unaware of the drug concentration used [4,10]. Observations at 10-min intervals after intrathecal injection included the following: 1 Placing reflex.…”

“…Intrathecal administration of magnesium sulphate (MgSO 4 ) has recently been shown to produce spinal anaesthesia [1][2][3]. Using the tail-pinch method, we have reported that intrathecal administration of MgSO 4 did not induce complete analgesia in the presence of motor paralysis [4] although differentiation of analgesia from motor paralysis may be difficult.…”

“…Using the tail-pinch method, we have reported that intrathecal administration of MgSO 4 did not induce complete analgesia in the presence of motor paralysis [4] although differentiation of analgesia from motor paralysis may be difficult. Hot-plate and mechanical stimulation tests have been used widely to test analgesic drugs [5].…”

“…We have therefore examined the effect of non-paralytic doses of MgSO 4 on antinociceptive action in acute pain models (Rand-Selitto mechanical method and hot-plate test), and in the formalin model in both the phasic and tonic periods.…”