Actions of Somatostatin on Rat Neocortical Neurons in vitro

The effects of somatostatin (SS14) on neocortical neurons of the rat were investigated in an in vitro slice preparation. Intracellular recordings were performed in neurons (n=30) in layers 2 and 3 of the frontal cortex. Iontophoretically applied SS14 reduced the responses evoked by iontophoretically applied L-glutamate (GLU) and gamma-aminobutyric acid (GABA). The blocking effect of SS14 was apparent 1 - 2 min after onset of SS14 application and recovery required 2 - 3 min. The conductance increase evoked by GLU or GABA was reduced by SS14. In the majority of neurons, SS14 did not produce any measurable changes in passive membrane properties, spike threshold or on orthodromically evoked synaptic potentials. In 5 cells, SS14 induced a slight hyperpolarization (<3 mV). These results lend further support to claims that SS14 plays a neuromodulatory role in the neocortex.