Bombesin-like peptides and associated receptors within the brain: distribution and behavioral implications.

As we commemorate the 25th anniversary of the journal Peptides, it is timely to review the functional significance of the bombesin (BB)-like peptides and receptors in the CNS. Over two decades ago we published an article in the journal Peptides demonstrating that BB-like peptides are present in high densities in certain rat brain regions (such as the paraventricular nucleus of the hypothalamus). Subsequently, one of the mammalian forms of BB, gastrin-releasing peptide (GRP) containing cell bodies were found in the suprachiasmatic nucleus of the hypothalamus and nucleus of the solitary tract of the hindbrain. Another related peptide, namely neuromedin (NM)B, was detected in the olfactory bulb and dentate gyrus. BB and GRP bind with high affinity to BB(2) receptors, whereas NMB binds with high affinity to BB(1) receptors. The actions of BB or GRP are blocked by BB(2) receptor antagonists such as (Psi(13,14)-Leu(14))BB whereas PD168368 is a BB(1) receptor antagonist. Exogenous administration of BB into the rat brain causes hypothermia, hyperglycemia, grooming and satiety. BB-like peptides activate the sympathetic nervous system and appear to modulate stress, fear and anxiety responses. GRP and NMB modulate distinct biological processes through discrete brain regions or circuits, and globally these peptidergic systems may serve in an integrative or homeostatic function.