Somatostatin hyperpolarizes neurons and inhibits spontaneous activity in the rat dorsolateral septal nucleus.
Intracellular recordings were made from rat brain neurons in a submerged slice preparation containing the dorsolateral septal nucleus (DLSN). Somatostatin-14 (SS-14) was applied to these neurons by superfusing solutions containing known concentrations of the peptide or by pressure ejection from micropipettes. With either method of treatment, SS-14 produced membrane hyperpolarization and decreased membrane resistance in a concentration-dependent manner. The hyperpolarizing response to SS-14 occurred in virtually all neurons tested and appeared to result from a direct action on DLSN neurons mediated by an increased permeability to potassium ions. The SS-14-induced membrane hyperpolarization was not blocked by naloxone, bicuculline, tetrodotoxin, or calcium-free, high-magnesium superfusion media. In a small number of neurons, SS-14 application produced a membrane depolarization which did not exhibit clear concentration-dependence and was blocked by superfusion of calcium-free, high-magnesium media indicating an indirect action. These findings reveal that SS-14 is a potent inhibitor of DLSN neurons in vitro and provide the first evidence that receptors for this putative neurotransmitter are located on postsynaptic neurons in this nucleus. Synaptically released SS-14 may play an important role in the modulation of septohippocampal function.
Twery
M J
MJ
Department of Pharmacology and Toxicology, University of Texas Medical Branch, Galveston 77550.
Gallagher
J P
JP
D000818:Animals; D001640:Bicuculline / Q000494:pharmacology; D001921:Brain / Q000187:drug effects / Q000502:physiology*; D002118:Calcium / Q000494:pharmacology; D004558:Electric Stimulation; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D009270:Naloxone / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D013004:Somatostatin / Q000494:pharmacology*; D013569:Synapses / Q000502:physiology; D013779:Tetrodotoxin / Q000494:pharmacology
D009270:Naloxone; D013779:Tetrodotoxin; D013004:Somatostatin; D008274:Magnesium; D002118:Calcium; D001640:Bicuculline