Emerging functions for tuberoinfundibular peptide of 39 residues.

Tuberoinfundibular peptide of 39 residues (TIP39), a neuropeptide recently purified from the hypothalamus, appears to be an endogenous ligand for the parathyroid hormone 2 (PTH2) receptor. PTH2 receptors are present in several central nervous system and peripheral areas and are particularly concentrated in the hypothalamus, limbic areas and the outer layers of the spinal cord dorsal horn. TIP39-containing neuronal cell bodies have been identified in the subparafascicular area and the medial paralemniscal nucleus, two brainstem regions that project widely through the entire neuraxis. Treatment of hypothalamic explants with TIP39, and intraventricular injection of the peptide, suggest that it might stimulate hypothalamic-releasing factor secretion. Injection of TIP39, and sequestration of endogenous TIP39 by intrathecal injection of an antibody to TIP39, have provided evidence that it is involved in some aspects of pain sensitivity. Thus, TIP39 might be a new neuromodulator.