Increased levels of cGMP, presumably acting in presynaptic terminals, promote long-lasting potentiation of GABA release at these synapses (Nugent morphine exposure has no effect on the presynaptic cAMP-PKA signaling pathway Our recent work has shown that treatment with morphine persistently modulates GABAergic synaptic plasticity as a result of interference with presynaptic NO-cGMP signaling (Nugent morphine with cAMP signaling in presynaptic terminals has the potential to interfere with synaptic potentiation from the cAMP-PKA pathway. Activation of nitric oxide synthase by intracellular Ca2+ produces NO, which then travels retrogradely to activate soluble guanylate cyclase (sGC) in neighboring presynaptic GABAergic nerve L-Lysine thioctate terminals. Improved levels of cGMP, presumably acting in presynaptic terminals, promote long-lasting potentiation of GABA launch at these synapses (Nugent morphine exposure has no effect on the presynaptic cAMP-PKA signaling pathway Our recent work has shown that treatment with morphine persistently modulates GABAergic synaptic plasticity as a result of interference with presynaptic NO-cGMP signaling (Nugent morphine with cAMP signaling in presynaptic terminals has the potential to interfere with synaptic potentiation from the cAMP-PKA pathway. To address this question, rats were treated either with morphine (10 mg/kg i.p.) or with saline and 24 hours after treatment, the effects of forskolin (10M) were tested on GABAergic synapses. Synapses from both saline- and morphine-treated animals were potentiated after exposure to forskolin (Number 8a-c) suggesting the presynaptic cAMP-PKA pathway is definitely unaltered after morphine exposure, in contrast to morphine’s effect on the NO-PKG signaling cascade involved in LTPGABA. This result also confirms that the site of disruption of the NO signaling by morphine is definitely upstream to the unidentified converging mechanism for both PKG and PKA. Open in a separate window Number 8 morphine does not modulate the presynaptic cAMP signaling cascadeRats were treated with either 10 mg/kg morphine or saline. 24 hours later, slices were prepared, and IPSCs were recorded from dopamine cells while 10 M forskolin was bath-applied. (a) Solitary experiment illustrating the potentiating effect of forskolin (10M) on IPSCs from a saline-treated animal. Inset: Averaged GABAA IPSCs recorded before (black) and after 20 moments in forskolin (reddish). Calibration for insets: 10ms, 100 pA. (b) Solitary experiment illustrating the effect of forskolin (10M) on IPSCs from a morphine-treated animal. Forskolin still potentiates GABAA-mediated IPSCs. Inset: Averaged GABAA IPSCs recorded before (black) and after 20 moments in forskolin (reddish). (c) Averaged experiments showing the enhancing effect of forskolin on IPSCs in slices from both saline- and morphine-treated animals, demonstrating that morphine does not alter the effect of forskolin (saline, packed circles, 188 11% of pre-drug ideals, n=8; morphine, open circles, 167 15% of pre-drug ideals, n=10). (d) Proposed model of signaling molecules involved in opioid-induced plasticity at VTA GABAergic synapses. An injection of morphine alters GABAergic plasticity through modulation of the NO signaling pathway, probably at the level of sGC, without affecting the cAMP signaling cascade. Conversation Here we have investigated the involvement of PKG and PKA in the induction and expression of LTPGABA. Furthermore, we provide evidence for the synapse-specificity of NO signaling at VTA GABAA synapses and confirm that morphine persistently and specifically modulates the plasticity of these synapses through an interaction with the NO signaling pathway without an associated switch in the coexistent cAMP signaling cascade. The NO-cGMP-PKG and cAMP-PKA signaling cascades both potentiate GABAergic synapses Increasing levels of NO exogenously using SNAP, or application of a cGMP analog, pCPT-cGMP, potentiates GABAergic synapses onto VTA DA neurons. Inhibition of PKG prevented the potentiation induced by NO or cGMP, supporting the role of PKG as the downstream effector from NO-cGMP. However, inhibition of PKG experienced no effect on basal GABAergic firmness suggesting that constitutive PKG activity is not necessary to maintain basal levels of GABA release. PKG is usually a serineCthreonine kinase that mediates most.Forskolin still potentiates GABAA-mediated IPSCs. promote long-lasting potentiation of GABA L-Lysine thioctate release at these synapses (Nugent morphine exposure has no effect on the presynaptic cAMP-PKA signaling pathway Our recent work has shown that treatment with morphine persistently modulates GABAergic synaptic plasticity as a result of interference with presynaptic NO-cGMP signaling (Nugent morphine with cAMP signaling in presynaptic terminals has the potential to interfere with synaptic potentiation by the cAMP-PKA pathway. To address this question, rats were treated either with morphine (10 mg/kg i.p.) or with saline and 24 hours after treatment, the effects of forskolin (10M) were tested on GABAergic synapses. Synapses from both saline- and morphine-treated animals were potentiated after exposure to forskolin (Physique 8a-c) suggesting that this presynaptic cAMP-PKA pathway is usually unaltered after morphine exposure, in contrast to morphine’s effect on the NO-PKG signaling cascade involved in L-Lysine thioctate LTPGABA. This result also confirms that the site of disruption of the NO signaling by morphine is usually upstream to the unidentified converging mechanism for both PKG and PKA. Open in a separate window Physique 8 morphine does not modulate the presynaptic cAMP signaling cascadeRats were treated with either 10 mg/kg morphine or saline. 24 hours later, slices were prepared, and IPSCs were recorded from dopamine cells while 10 M forskolin was bath-applied. (a) Single experiment illustrating the potentiating effect of forskolin (10M) on IPSCs from a saline-treated animal. Inset: Averaged GABAA IPSCs recorded before (black) and after 20 moments in forskolin (reddish). Calibration for insets: 10ms, 100 pA. (b) Single experiment illustrating the effect of forskolin (10M) on IPSCs from a morphine-treated animal. Forskolin still potentiates GABAA-mediated IPSCs. Inset: Averaged GABAA IPSCs recorded before (black) and after 20 moments in forskolin (reddish). (c) Averaged experiments showing the enhancing effect of forskolin on IPSCs in slices from both saline- and morphine-treated animals, demonstrating that morphine does not alter the effect of forskolin L-Lysine thioctate (saline, packed circles, 188 11% of pre-drug values, n=8; morphine, open circles, 167 15% of pre-drug values, n=10). (d) Proposed model of signaling molecules involved in opioid-induced plasticity at VTA GABAergic synapses. An injection of morphine alters GABAergic plasticity through modulation of the NO signaling pathway, probably at the level of sGC, without affecting the cAMP signaling cascade. Conversation Here we have investigated the involvement of L-Lysine thioctate PKG and PKA in the induction and expression of LTPGABA. Furthermore, we provide evidence for the synapse-specificity of NO signaling at VTA GABAA synapses and confirm that GPATC3 morphine persistently and specifically modulates the plasticity of these synapses through an interaction with the NO signaling pathway without an associated switch in the coexistent cAMP signaling cascade. The NO-cGMP-PKG and cAMP-PKA signaling cascades both potentiate GABAergic synapses Increasing levels of NO exogenously using SNAP, or application of a cGMP analog, pCPT-cGMP, potentiates GABAergic synapses onto VTA DA neurons. Inhibition of PKG prevented the potentiation induced by NO or cGMP, supporting the role of PKG as the downstream effector from NO-cGMP. However, inhibition of PKG experienced no effect on basal GABAergic firmness suggesting that constitutive PKG activity is not necessary to maintain basal levels of GABA release. PKG is usually a serineCthreonine kinase that mediates most of the effects of cGMP. Two different classes of PKG have been reported, PKG I and PKG II. While PKG I is usually highly localized in cerebellar Purkinje cells and a few other sites in brain, the ubiquitous distribution of PKG II and its major localization in neuronal processes make it a major target in mediating.
