Stimulatory effects of bombesin-like peptides on suprachiasmatic neurons in brain slices.
The effects of bombesin on hypothalamic suprachiasmatic (SCN) neurons were tested in this study using extracellular single-unit recording in brain tissue slices. Fresh slices containing the SCN were obtained from adult ovariectomized Sprague-Dawley rats. Bombesin in pmol ranges stimulated 75% of irregular firing SCN neurons (n = 113), while it stimulated and inhibited 17% and 34% of regular firing units, respectively. Half of the regular firing SCN units, however, were not responsive to bombesin (49% of 61 units). A dose-dependent (from 5 to 500 pmol) excitatory effect of bombesin on SCN neurons was also observed. Pretreatment with [Leu13-psi(CH2NH)-Leu14]-bombesin, a bombesin receptor antagonist, blocked the action of bombesin in 67% of 18 units responded to bombesin, indicating a specific receptor is involved in the action. Gastrin-releasing peptide, a well-recognized bombesin-like peptide in mammals, behaved almost the same as bombesin did in most SCN neurons tested (same responses in 24 of 25 units). The present finding indicates that bomesin-like peptides may play a significant role in the SCN for the rhythmic control mechanism.
Institute of Physiology, National Yang-Ming Medical College, Taipei, Taiwan Republic of China.
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D000818:Animals; D001839:Bombesin / Q000031:analogs & derivatives / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D005260:Female; D019886:Gastrin-Releasing Peptide; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects*; D010455:Peptides / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter / Q000187:drug effects; D013268:Stimulation, Chemical; D013493:Suprachiasmatic Nucleus / Q000166:cytology / Q000187:drug effects*
D010455:Peptides; D018004:Receptors, Bombesin; D017981:Receptors, Neurotransmitter; C057644:bombesin, Leu(13)-psi-CH2NH-Leu(14)-; D019886:Gastrin-Releasing Peptide; D008274:Magnesium; D001839:Bombesin; D002118:Calcium