Analgesic, respiratory and endocrine responses in normal man to THIP, a GABA-agonist

In a controlled study, the effects of THIP (a synthetic gamma-aminobutyric-acid-agonist) on respiratory function (ventilatory response to CO2), first detection of stimulation (electrical stimulation of a tooth), pain threshold, magnitude of maximal tolerated pain stimulation, and plasma cortisol, prolactin and glucose were investigated in six normal men. Intramuscular injection of THIP in dosages of both 10 mg and 20 mg increased the magnitude of stimulus before first detection, and the pain threshold as well as the maximal tolerance of pain stimulation. THIP did not lead to changes in respiratory function, or in plasma cortisol, prolactin or glucose, suggesting an analgesic action independent of opiate receptors.