Long-term potentiation (LTP) is considered a cellular correlate of learning and memory. The presence of G protein-activated inwardly rectifying K(+) (GIRK) channels near excitatory synapses on dendritic spines suggests their possible involvement in synaptic plasticity. However, whether activity-dependent regulation of channels affects excitatory synaptic plasticity is unknown. In a companion article we have reported activity-dependent regulation of GIRK channel density in cultured hippocampal neurons that requires activity oF receptors (NMDAR) and protein phosphatase-1 (PP1) and takes place within 15 min. In this study, we performed whole-cell recordings of cultured hippocampal neurons and found that NMDAR activation increases basal GIRK current and GIRK channel activation mediated by adenosine A(1) receptors, but not GABA(B) receptors. Given the similar involvement of NMDARs, adenosine receptors, and PP1 in depotentiation of LTP caused by low-frequency stimulation that immediately follows LTP-inducing high-frequency stimulation, we wondered whether NMDAR-induced increase in GIRK channel surface density and current may contribute to the molecular mechanisms underlying this specific depotentiation. Remarkably, GIRK2 null mutation or GIRK channel blockade abolishes depotentiation of LTP, demonstrating that GIRK channels are critical for depotentiation, one form of excitatory synaptic plasticity.
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Answer:
B) Multicellular Simple gland
Explanation:
Exocrine Glands:Glands that secrete their products onto the apical(or epithelia) surface directly or via epithelial ducts or tubes that are connected to the apical surface. These Exocrine glands are composed of highly specialized epithelial cells..
Exocrine glands can either be branched or Unbranched based on the arrangement.
*Multicellular simple glands*:Glands that have an *unbranched duct* into which cells secrete. Each secretory portion empties separately on an epithelial surface.
They have body fat level in the MARGINAL OR BORDERLINE ZONE. At this zone, the fat level in the body is higher than the acceptable levels but is less that the fat levels in the obese people. With this level of fat, one has higher risks for such diseases such as high blood pressure, heart diseases, etc.
D) earthquake
Earthquakes release gases into the atmosphere.
