Moderate anticonvulsant action of baclofen does not change during development.

The possible anticonvulsant action of baclofen, a GABAB (gamma-aminobutyric acid) receptor agonist, was studied using two types of motor seizures (minimal, clonic and generalized tonicoclonic) elicited by pentylenetetrazol in adult rats and rat pups, 7, 12, 18, and 25 days old. If baclofen was administered intraperitoneally (only in 12- and 25-day-old rats), no effect could be observed in 25-day-old animals. In 12-day-old rats, only the 12-mg/kg dose led to a prolongation of the generalized tonicoclonic seizure latency. Subcutaneous administration of baclofen (3, 6, or 12 mg/kg 30 min before subcutaneous pentylenetetrazol injection) led to a moderate action against the tonic phase of generalized tonicoclonic seizures: the tonic phase of hind limbs was significantly suppressed in all age groups, whereas total suppression of the tonic phase was only outlined. Minimal, i.e., clonic, seizures with preserved righting ability were not influenced by baclofen. The conclusion could be made that the anticonvulsant action of baclofen is dependent on the model of seizures used and that there is no change of baclofen action against pentylenetetrazol-induced seizures during postnatal development in rats.