“Hippocampal inhibitory interneurons have a central role i

“Hippocampal inhibitory interneurons have a central role in the control of network activity,

and excitatory synapses that they receive express Hebbian and anti-Hebbian long-term potentiation (LTP). Because many interneurons in the hippocampus express nicotinic acetylcholine receptors (nAChRs), we explored whether exposure to nicotine promotes LTP induction in these interneurons. We focussed on a subset of interneurons in the stratum oriens/alveus that were continuously activated in the presence of nicotine due to the expression of non-desensitizing non-α7 nAChRs. We found that, in addition to α2 subunit mRNAs, these interneurons were consistently positive for somatostatin and neuropeptide Y mRNAs, and http://www.selleckchem.com/products/apo866-fk866.html showed morphological characteristics of oriens-lacunosum moleculare cells. Activation of non-α7 nAChRs increased intracellular Ca2+ levels at least in part via Ca2+ entry through their channels. Presynaptic tetanic stimulation induced N-methyl-d-aspartate receptor-independent LTP in voltage-clamped interneurons at −70 mV when in the presence, but not absence, of nicotine. Intracellular application of a Ca2+ chelator blocked LTP induction, suggesting the requirement of Ca2+ signal for LTP induction. The Inhibitor Library cell assay induction of LTP was still observed in the presence of ryanodine, which inhibits Ca2+ -induced

Ca2+ release from ryanodine-sensitive intracellular stores, and the L-type Ca2+ channel blocker nifedipine. These results

suggest that Ca2+ entry through non-α7 nAChR channels is critical for LTP induction. Thus, nicotine affects hippocampal network activity by promoting LTP induction in oriens-lacunosum moleculare cells via continuous activation of non-α7 nAChRs. “
“Kisspeptin signaling via the kisspeptin receptor G-protein-coupled receptor-54 plays a fundamental role in the onset of puberty and the regulation of mammalian reproduction. In this immunocytochemical study we addressed the (i) topography, (ii) sexual dimorphism, (iii) relationship to gonadotropin-releasing Pyruvate dehydrogenase hormone (GnRH) neurons and (iv) neurokinin B content of kisspeptin-immunoreactive hypothalamic neurons in human autopsy samples. In females, kisspeptin-immunoreactive axons formed a dense periventricular plexus and profusely innervated capillary vessels in the infundibular stalk. Most immunolabeled somata occurred in the infundibular nucleus. Many cells were also embedded in the periventricular fiber plexus. Rostrally, they formed a prominent periventricular cell mass (magnocellular paraventricular nucleus). Robust sex differences were noticed in that fibers and somata were significantly less numerous in male individuals. In dual-immunolabeled specimens, fine kisspeptin-immunoreactive axon varicosities formed axo-somatic, axo-dendritic and axo-axonal contacts with GnRH neurons.

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