Different basal levels of CaMKII phosphorylated at Thr286/287 at nociceptive and low-threshold primary afferent synapses.
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.
Larsson
Max
M
Department of Experimental Medical Science, Division of Neuroscience, Lund University, BMC F10, SE-221 84 Lund, Sweden. max.larsson@mphy.lu.se
Broman
Jonas
J
D000818:Animals; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism*; D006930:Hyperalgesia / Q000378:metabolism*; D008297:Male; D016253:Microscopy, Immunoelectron; D009619:Nociceptors / Q000201:enzymology* / Q000648:ultrastructure; D010477:Perfusion; D010766:Phosphorylation; D020671:Posterior Horn Cells / Q000201:enzymology* / Q000648:ultrastructure; D051381:Rats; D017207:Rats, Sprague-Dawley; D013569:Synapses / Q000201:enzymology; D013912:Threonine / Q000378:metabolism; D015854:Up-Regulation
D013912:Threonine; D054732:Calcium-Calmodulin-Dependent Protein Kinase Type 2; D017871:Calcium-Calmodulin-Dependent Protein Kinases