Effect of sodium valproate on the spontaneous contractile and bioelectric activity of smooth muscle fibres isolated from experimental animals.
Experiments were carried out with smooth muscles preparations of 24 rats (gastric corpus) and 36 guinea pigs (gastric corpus and taenia coli). Their contractile responses were recorded isometrically using tensile transducers. The bioelectric activity was determined by the single sucrose-gap method. Depending on the concentration sodium valproate elicits two types of responses from the smooth muscle of gastrointestinal tract of rats and guinea pigs: a contractile response, at concentrations less than 10(-4) g/ml, and a relaxant response, at concentrations higher than 10(-4) g/ml. At concentrations below 10(-4) g/ml sodium valproate induces contractions of the smooth muscle taken from the rat and guinea pig gastrointestinal tract. These contractions can be abolished by indomethacin. It may be concluded, therefore, that the contractile effect of sodium valproate has a prostaglandin basis. At concentrations higher than 10(-4) g/ml, sodium valproate hyperpolarizes the smooth muscle tissues, reduces the frequency and amplitude of the spontaneously generated spike potentials and relaxes the preparations. These effects are blocked by picrotoxin. Sodium valproate in high concentrations increases the endogenous level of the gamma-aminobutyric acid stimulating at the same time the prostaglandin synthesis which is inadequate to compensate the relaxant effect induced by elevated level of the endogenous gamma-aminobutyric acid.
Kristev
A
A
Department of Biophysics, Medical University, Plovdiv, Bulgaria.
Peichev
L
L
Zaprianov
G
G
Lukanov
J
J
D000818:Animals; D000927:Anticonvulsants / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D014635:Valproic Acid / Q000494:pharmacology*
D000927:Anticonvulsants; D014635:Valproic Acid