Different basal levels of CaMKII phosphorylated at Thr286/287 at nociceptive and low-threshold primary afferent synapses

Eur J Neurosci. 2005 May;21(9):2445-58. doi: 10.1111/j.1460-9568.2005.04081.x.


Postsynaptic autophosphorylation of Ca2+/calmodulin-dependent protein kinase II (CaMKII) at Thr286/287 is crucial for the induction of long-term potentiation at many glutamatergic synapses, and has also been implicated in the persistence of synaptic potentiation. However, the availability of CaMKII phosphorylated at Thr286/287 at individual glutamatergic synapses in vivo is unclear. We used post-embedding immunogold labelling to quantitatively analyse the ultrastructural localization of CaMKII phosphorylated at Thr286/287 (pCaMKII) at synapses formed by presumed nociceptive and low-threshold mechanosensitive primary afferent nerve endings in laminae I-IV of rat spinal cord. Immunogold labelling was enriched in the postsynaptic densities of such synapses, consistent with observations in pre-embedding immunoperoxidase-stained dorsal horn. Presynaptic axoplasm also exhibited sparse immunogold labelling, in peptidergic terminals partly associated with dense core vesicles. Analysis of single or serial pCaMKII-immunolabelled sections indicated that the large majority of synapses formed either by presumed peptidergic or non-peptidergic nociceptive primary afferent terminals in laminae I-II of the spinal cord, or by presumed low-threshold mechanosensitive primary afferent terminals in laminae IIi-IV, contained pCaMKII in their postsynaptic density. However, the postsynaptic levels of pCaMKII immunolabelling at low-threshold primary afferent synapses were only approximately 50% of those at nociceptive synapses. These results suggest that constitutively autophosphorylated CaMKII in the postsynaptic density is a common characteristic of glutamatergic synapses, thus potentially contributing to maintenance of synaptic efficacy. Furthermore, pCaMKII appears to be differentially regulated between high- and low-threshold primary afferent synapses, possibly reflecting different susceptibility to synaptic plasticity between these afferent pathways.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases / metabolism*
  • Hyperalgesia / metabolism*
  • Male
  • Microscopy, Immunoelectron
  • Nociceptors / enzymology*
  • Nociceptors / ultrastructure
  • Perfusion
  • Phosphorylation
  • Posterior Horn Cells / enzymology*
  • Posterior Horn Cells / ultrastructure
  • Rats
  • Rats, Sprague-Dawley
  • Synapses / enzymology
  • Threonine / metabolism
  • Up-Regulation


  • Threonine
  • Calcium-Calmodulin-Dependent Protein Kinase Type 2
  • Calcium-Calmodulin-Dependent Protein Kinases