Somatostatin-14 and somatostatin-28 induce opposite effects on potassium currents in rat neocortical neurons.

AUTOR(ES)

Wang, H L

RESUMO

The prosomatostatin-derived peptides somatostatin-14 (Som-14) and somatostatin-28 (Som-28) are believed to act as neurotransmitters in the central nervous system. To examine possible mechanisms by which these peptides induce their physiological actions in brain, the effects of Som-14 and Som-28 on voltage-dependent K+ currents in rat cerebral cortical neurons in culture were examined by using whole-cell patch-clamp techniques. Som-14 increased a delayed rectifier K+ current (IK) in the cortical neurons, while Som-28 reduced IK in the neurons, both in a concentration-dependent manner. Som-14 and Som-28 could induce opposite changes in IK in the same neurons. Elevating intracellular cAMP in the cortical neurons did not modify the effects of Som-14 or Som-28 on IK, indicating that the peptides can regulate this ionic current through cAMP-independent mechanisms. Pretreatment of the neocortical cells with pertussis toxin, which inactivates inhibitory GTP-binding proteins, abolished both Som-14 and Som-28 modulation of IK, indicating that Som-14 and Som-28 receptors are coupled to IK via GTP-binding proteins. These studies show that Som-14 and Som-28 can induce opposite biological effects, suggesting that Som-14 and Som-28, acting through distinct receptors, may function as different neurotransmitters or neuromodulators.

Documentos Relacionados

• A high molecular weight form of somatostatin-28 (1-12)-like immunoreactive substance without somatostatin-14 immunoreactivity in the rat pancreas. Evidence that somatostatin-14 synthesis can occur independently of somatostatin-28.
• Selective binding of somatostatin-14 and somatostatin-28 to islet cells revealed by quantitative electron microscopic autoradiography.
• Molecular cloning of a somatostatin-28 receptor and comparison of its expression pattern with that of a somatostatin-14 receptor in rat brain.
• Enzymes processing somatostatin precursors: an Arg-Lys esteropeptidase from the rat brain cortex converting somatostatin-28 into somatostatin-14.
• Action potential initiation and propagation in rat neocortical pyramidal neurons.