Somatostatin: central nervous system actions on glucoregulation

Area of Science:

• Neuroendocrinology
• Metabolic Regulation
• Pharmacology

Background:

• Somatostatin (SRIF) plays a role in central nervous system (CNS) regulation of glucose metabolism.
• Systemic administration of SRIF is often ineffective in altering glucoregulation.
• Intracisternal (ic) administration allows direct access to the CNS for studying SRIF's effects.

Purpose of the Study:

• To investigate the central effects of Somatostatin (SRIF) and its analogs on glucoregulation.
• To determine if SRIF analogs administered intracisternally can prevent hyperglycemia induced by various stimuli.
• To compare the potency of different SRIF analogs in modulating central glucoregulatory pathways.

Main Methods:

• Administration of Somatostatin (SRIF) and its analogs intracisternally (ic) in rats.
• Induction of hyperglycemia using bombesin, beta-endorphin, carbachol, surgical stress, epinephrine, arginine, or glucagon.
• Measurement of plasma glucose, insulin, and glucagon levels.
• Comparison of the effects of ic vs. systemic administration of SRIF analogs.

Main Results:

• Intracisternal (ic) SRIF and analogs reduced hyperglycemia and hyperglucagonemia induced by ic bombesin, even at systemically ineffective doses.
• A specific SRIF analog, des-AA1, 2, 4, 5, 12, 13-[D-Trp8]SRIF, was 10 times more potent than SRIF in preventing bombesin-induced hyperglycemia when given ic.
• This analog also prevented hyperglycemia from surgical stress, ic beta-endorphin, or ic carbachol, but not from systemic epinephrine, arginine, or glucagon.

Conclusions:

• Somatostatin (SRIF) and its analogs act within the central nervous system (brain) to regulate glucose metabolism.
• Intracisternal administration of specific SRIF analogs can effectively counteract centrally mediated hyperglycemia.
• The findings highlight the potential of targeting central SRIF pathways for managing hyperglycemia.