title: Further studies of the effects of somatostatin and related peptides in area CA1 of rabbit hippocampus.
abstract: 1. In slice studies of mature and immature CA1 hippocampal pyramidal cells from rabbit, somatostatin 14 (SS14), the related peptide somatostatin 28(1-12) [SS(1-12)], and the synthetic analogue of somatostatin 14, SMS-201995 (SMS), had similar effects. When pressure-ejected onto cell somata, these peptides elicited depolarizations, often accompanied by action potential discharge. When applied to dendrites, the peptides produced depolarizations or hyperpolarizations. 2. When a large amount of one of the three somatostatin-related (SS) peptides was applied to the slice at some distance from the impaled cell, hyperpolarizations were observed that were not always blocked by tetrodotoxin (TTX) or low Ca2+. Since SS peptides were also found to depolarize interneurons in area CA1, it seems likely that the hyperpolarizations that were blocked by TTX or low Ca2+ were mediated via excitation of interneurons that in turn hyperpolarized pyramidal cells. 3. All SS peptides also had long-lasting effects on CA1 pyramidal cells that led to spontaneous firing of action potentials and an increase in the number of action potentials discharged in response to a given depolarizing current pulse; the spontaneous discharge effect was blocked by TTX or low Ca2+ plus Mn2+ and, thus, appeared to have a presynaptic mechanism. However, the increase in discharge in response to a constant depolarizing current pulse was not dependent on intact synaptic transmission and, therefore, was attributable to a direct postsynaptic effect of the SS peptides.
authors.affiliation: Department of Neurological Surgery, University of Washington, Seattle 98195.
authors.forename: H E
authors.initials: HE
authors.lastname: Scharfman
authors.forename: P A
authors.initials: PA
authors.lastname: Schwartzkroin
mesh_terms: D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D003712:Dendrites / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007395:Interneurons / Q000187:drug effects / Q000502:physiology; D008297:Male; D015282:Octreotide / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011817:Rabbits; D013004:Somatostatin / Q000494:pharmacology*; D053561:Somatostatin-28
chemical_list: D010446:Peptide Fragments; D013004:Somatostatin; D053561:Somatostatin-28; C037197:somatostatin 28-(1-12); D015282:Octreotide