The acute effect of the GABA-agonist, THIP, on proprioceptive and flexor reflexes in spastic patients

THIP (Lu 2-030) is pharmacologically a specific and potent GABA-receptor-agonist which in animal studies depresses monosynaptic and, to a smaller extent, polysynaptic spinal reflexes. 5 spastic patients were investigated by means of neurophysiological tests comparing the acute effect of a single oral dose of THIP (15-25 mg) to "the test situation without drug administration" with an interval of 2 days. The neurophysiological tests included quantitative studies of proprioceptive reflexes (T-reflex, vibratory inhibition of the T-reflex, resistance to passive movement of a spastic muscle and clonus) and of the flexor reflex (threshold and latency). The voluntary power was measured by a static technique. THIP clearly reduced the monosynaptic T-reflex and reinforced vibratory inhibition of the IA monosynaptic pathway. The flexor reflex threshold was slightly increased during THIP administration, but the changes were not significant. Flexor reflex latency, resistance to passive movement, clonus and voluntary power were unchanged.