substance-p--pro(2)-phe(7)-trp(9)- and Muscle-Spasticity

Microinjections of the substance P (SP) antagonist (D-pro2,D-phe7,D-trp9)-SP, or the gamma-aminobutyric acid (GABA) agonist, muscimol, into the entopeduncular nucleus reduced muscle tone in genetically spastic rats in a dose- and time-dependent manner. Similar injections into the ventral thalamus, zona incerta or amygdala had no effect on muscle tone. The muscle relaxant effect of (D-pro2,D-phe7,D-trp9)-SP injected into the entopeduncular nucleus was blocked by co-injections of SP, and that of muscimol by the GABAA antagonist, bicuculline methiodide. These results suggest that SP- and GABA-dependent mechanisms in the entopeduncular nucleus mediate regulation of the muscle tone.

Topics: Animals; Female; gamma-Aminobutyric Acid; Globus Pallidus; Male; Muscimol; Muscle Spasticity; Muscle Tonus; Rats; Rats, Inbred Strains; Substance P