Thyrotropin secretion in rats after hypothalamic electrical stimulation or injection of synthetic TSH-releasing...

Plasma thyroid-stimulating hormone (TSH) levels, as measured by radioimmunoassay, begin to rise within 5 minutes after initiation of electrical stimulation of the medial-basal hypothalamus, become significantly elevated at 10 minutes, and reach a peak at 10 to 25 minutes. Intravenous administration of synthetic thyrotropin-releasing factor induces a marked rise in plasma thyroidstimulating hormone which is maximal within 5 minutes after administration. These data are interpreted to indicate that there are neuronal structures within the medial-basal hypothalamus which release preformed thyrotropin-releasing factor. The claim (based on bioassay data) that pyroglutamyl-histidyl-proline amide is a potent thyrotropin-releasing factor has also been confirmed by using a highly specific immunoassay system.