Effects of Systemic Injections of Gamma-Hydroxybutyrate on the Recovery of Functions of the Distal Hindlimb Muscles in Rats after Compression of the Sciatic Nerve

Abstract

We studied the effects of systemic injections of sodium gamma-hydroxybutyrate (GHB; 100 mg/kg, i.p., daily for 4 weeks) on the recovery of contractions of the distal hindlimb extensors and flexors after compression of the sciatic nerve in the rat. We also analyzed the dynamics of the functional sciatic index (FSI) and of the recovery of the contractile force (the latter index was estimated using tensometric transducers). In the control group, rats were also subjected to traumatic compression of the sciatic nerve but with no GHB injections. In the experimental GHB group, the recovery of the muscle activity was accelerated on the side of compression of the nerve; the rates of such recovery in various muscles were dissimilar. The indices of contractile activity of extensors of the foot and toes recovered on the 4th week (8 weeks earlier than in the control), while the contractile force of the toe flexors recovered on the 3rd week (7 weeks earlier). Within the late time intervals (10th and 12th weeks) after surgical intervention, the contractile force of the right foot extensors increased (by 40 and 30%, respectively, as compared with the control), while the flexors demonstrated only 5 and 4% increases. In the left (intact) hindlimb, the contractile force of flexors and extensors, beginning from the 3rd week, increased significantly (by 20-40%, as compared with the control). Within the late time intervals after traumatization, the GHB-influenced muscle contraction was not only greater than that in the control but also exceeded the initial values before surgical intervention. Therefore, the effect of GHB with respect to the contralateral (intact) hindlimb was manifested as an increment of the contractile force (in extensors, by 26 and 20% on the 10th and 12th week, and in flexors, respectively, by 48 and 36%). The probable mechanisms underlying the positive effect of GHB on the processes of recovery of the functional activity of peripheral nerves and muscle contractile force are discussed.