Calcium/calmodulin-dependent kinase II mediates NO-elicited PKG activation to participate in spinal reflex potentiation in anesthetized rats

Abstract

Calcium/calmodulin protein kinase (CaMK)-dependent nitric oxide (NO) and the downstream intracellular messenger cGMP, which is activated by soluble guanylate cyclase (sGC), are believed to induce long-term changes in efficacy of synapses through the activation of protein kinase G (PKG). The aim of this study was to examine the involvement of the CaMKII-dependent NO/sGC/PKG pathway in a novel form of repetitive stimulation-induced spinal reflex potentiation (SRP). A single-pulse test stimulation (TS; 1/30 Hz) on the afferent nerve evoked a single action potential, while repetitive stimulation (RS; 1 Hz) induced a long-lasting SRP that was abolished by a selective Ca 2ϩ /CaMKII inhibitor, autocamtide 2-related inhibitory peptide (AIP). Such an inhibitory effect was reversed by a relative excess of nitric oxide synthase (NOS) substrate, L-arginine. In addition, the RS-induced SRP was abolished by pretreatment with the NOS inhibitor, N G -nitro-L-arginine-methyl ester (L-NAME). The sGC activator, protoporphyrin IX (PPIX), reversed the blocking effect caused by L-NAME. On the other hand, a sGC blocker, 1H-[1, 2, 4]oxadiazolo[4, 3-␣]quinoxalin-1-one (ODQ), abolished the RS-induced SRP. Intrathecal applications of the membrane-permeable cGMP analog, 8-bromoguanosine 3Ј,5Ј-cyclic monophosphate sodium salt monohydrate (8-Br-cGMP), reversed the blocking effect on the RS-induced SRP elicited by the ODQ. Our findings suggest that a CaMKII-dependent NO/sGC/PKG pathway is involved in the RSinduced SRP, which has pathological relevance to hyperalgesia and allodynia.spinal reflex potentiation; soluble guanylate cyclase; cyclic monophosphate sodium salt monohydrate; spinal cord; windup ACTIVITY-DEPENDENT REFLEX plasticity, the dynamic regulation of reflex strength by ongoing neural activities, is a fundamental component of normal CNS functions. Long-term potentiation (LTP), a form of well-known activity-dependent reflex potentiation in synaptic responses that occurs in the CA1 area of the hippocampus, is considered the base for some forms of learning and memory (45). In the hippocampal CA1 region, LTP is induced by brief tetanic stimulation of afferent glutamatergic fibers and is typically dependent on activation of postsynaptic N-methyl-D-aspartate (NMDA) receptors (3).A key-initiating event in LTP induction is the activation of Ca 2ϩ /calmodulin protein kinase II (CaMKII) (14, 44, 30; 54). An increase in the intracellular Ca 2ϩ concentration, partly by the influx through NMDA receptor channels, activates calmodulin, which in turn triggers the activation of CaMKII, causing it to bind to the postsynaptic density. It is a well-known fact that nitric oxide (NO) stimulates soluble guanylyl cyclase, and, in turn, produces intracellular cGMP and subsequently activates the protein kinase G (PKG) to induced activity-dependent reflex potentiation (53). Brenman and Bredt (6) reported that NO can be activated by CaMKII. Several investigators revealed that NO plays a role in LTP as indicated by experiments showing that LTP is eliminated or...

Estrogen-dependent facilitation on spinal reflex potentiation involves the Cdk5/ERK1/2/NR2B cascade in anesthetized rats

“…Although the physiological/pathophysiological relevance is still being sought for final proof, the induction of SRP has been linked to the development of neuropathic/postinflammatory visceral pain in the pelvic area, for it is characterized by pathological enhancement in urethra activity caused by the activation of nociceptive afferent fibers. (12,14,46,47,71).…”

Molecular Assays for Characterization of Alternatively Spliced Isoforms of the Mu Opioid Receptor (MOR)

“…It has also been established that the activation of cAMP and cGMP cascades through Ca 2+ -dependent activation of nitric oxide synthase leads to activation of protein kinases A (PKA) and G (PKG) and establishment of a pronociceptive phenotype (27). The increased influx of Ca 2+ leads to activation of nitric oxide synthase through Ca-calmodulin dependent mechanism resulting in increased production of NO (28). In turn, increased levels of NO stimulate guanylyl cyclase, leading to the production of cGMP, activation of PKG, and establishment of a pro-nociceptive phenotype (28).…”

“…The increased influx of Ca 2+ leads to activation of nitric oxide synthase through Ca-calmodulin dependent mechanism resulting in increased production of NO (28). In turn, increased levels of NO stimulate guanylyl cyclase, leading to the production of cGMP, activation of PKG, and establishment of a pro-nociceptive phenotype (28). In agreement with this, the newly cloned human 5′-end alternatively spliced isoform of MOR-3 that codes for six transmembrane variant rather than the classic seven transmembrane variant, exhibited a dose-dependent release of NO following treatment with morphine (8).…”

Estrous cycle variation of TRPV1-mediated cross-organ sensitization between uterus and NMDA-dependent pelvic-urethra reflex activity

“…The pelvic-urethra reflex, which is the reflexive closure of the urethra caused by bladder distension, is the neural basis for urine continence (15,16,17,22,35,36,48,49,50). Neurogenic hyperactivity and/or dyssynergia are believed to be participants in lower urinary tract dysfunctions, including interstitial cystitis (19,47).…”