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Previously we observed differential activation in individual columns of the periaqueductal grey (PAG) during breathlessness and its conditioned anticipation (Faull et al., 2016). Here, we have extended this work by determining how the individual columns of the PAG interact with higher cortical centres, both at rest and in the context of breathlessness threat. Activation was observed in ventrolateral PAG (vlPAG) and lateral PAG (lPAG), where activity scaled with breathlessness intensity ratings, revealing a potential interface between sensation and cognition during breathlessness. At rest the lPAG was functionally correlated with cortical sensorimotor areas, conducive to facilitating fight/flight responses, and demonstrated increased synchronicity with the amygdala during breathlessness. The vlPAG showed fronto-limbic correlations at rest, whereas during breathlessness anticipation, reduced functional synchronicity was seen to both lPAG and motor structures, conducive to freezing behaviours. These results move us towards understanding how the PAG might be intricately involved in human responses to threat

Optimization of Microwave Networks by Razor Search

[121] G. C. Broyden, “A new method of solving nonlinear simultaneou

μ-opioid receptor modulation of calcium channel current in periaqueductal grey neurons from C57B16/J mice and mutant mice lacking MOR-1

1. The actions of opioid receptor agonists on the calcium channel currents (I(Ba)) of acutely dissociated periaqueductal grey (PAG) neurons from C57B16/J mice and mutant mice lacking the first exon of the μ-opioid receptor (MOR-1) were examined using whole cell patch clamp techniques. These effects were compared with the GABA(B)-receptor agonist baclofen. 2. The endogenous opioid agonist methionine-enkephalin (met-enkephalin, pEC(50) 6.8, maximum inhibition 40%), the putative endogenous μ-opioid agonist endomorphin-1 (pEC(50) 6.2, maximum inhibition 35%) and the μ-opioid selective agonist DAMGO (Tyr-D-Ala-Gly-N-Me-Phe-Gly-ol enkephalin, pEC(50) 6.9, maximum inhibition 40%) inhibited I(Ba) in 70% of mouse PAG neurons. The inhibition of I(Ba) by each agonist was completely prevented by the μ-receptor antagonist CTAP (D-Phe-Cys-Tyr-D-Trp-Arg-Thr-Pen-Thr-NH(2)). The δ-opioid receptor agonists DPDPE ([D-Pen(2,5)]-enkephalin, 1 μM) and deltorphin II (1 μM), and the κ-opioid receptor agonist U-69593 (1–10 μM), did not affect I(Ba) in any cell tested. 3. The GABA(B) agonist baclofen inhibited I(Ba) in all neurons (pEC(50) 5.9, maximum inhibition 42%). 4. In neurons from the MOR-1 deficient mice, the μ-opioid agonists met-enkephalin, DAMGO and endomorphin-1 did not inhibit I(Ba), whilst baclofen inhibited I(Ba) in a manner indistinguishable from wild type mice. 5. A maximally effective concentration of endomorphin-1 (30 μM) partially (19%), but significantly (P<0.005), occluded the inhibition of I(Ba) normally elicited by a maximally effective concentration of met-enkephalin (10 μM). 6. This study indicates that μ-opioid receptors, but not δ- or κ-opioid receptors, modulate somatic calcium channel currents in mouse PAG neurons. The putative endogenous μ-agonist, endomorphin-1, was a partial agonist in mouse PAG neurons

Cellular actions of opioids on periaqueductal grey neurons from C57B16/J mice and mutant mice lacking MOR-1

1. Patch clamp recordings were made from periaqueductal grey (PAG) neurons in vitro to investigate the cellular actions of opioids in wild-type C57B16/J mice and mutant mice lacking the first exon of the μ-opioid (MOP) receptor. 2. In wild-type mice, the κ-(KOP) agonist U-69593 (300 nM) and the mixed μ/δ-opioid agonist met-enkephalin (10 μM), but not the δ-(DOP) agonist deltorphin (300 nM), reduced the amplitude of evoked GABA(A)-mediated inhibitory postsynaptic currents (IPSCs). Met-enkephalin and U-69593 also reduced the rate of spontaneous miniature IPSCs, but had no effect on their amplitude and kinetics. In μ-receptor-deleted mice, only U-69593 (300 nM) reduced the amplitude of evoked IPSCs. 3. In wild-type mice, the MOP agonist DAMGO (3 μM) produced an outward current in 76% of the neurons. Deltorphin and U-69593 produced outward currents in 24 and 32% of the neurons, respectively. In μ-receptor-deleted mice, deltorphin and U-69593 produced similar outward currents in 32 and 27% of the neurons, respectively, while DAMGO was without effect. All neurons in both the wild-type and μ-receptor-deleted mice responded with similar outward currents to either the GABA(B) receptor agonist baclofen (10 μM), or the opioid-like receptor ORL1 (NOP) agonist nociceptin (300 nM). 4. The DAMGO-, deltorphin-, U-69593-, baclofen- and nociceptin-induced currents displayed inward rectification and reversed polarity at −109 to −116 mV. 5. These findings indicate that μ-, δ- and κ-opioid receptor activation has complex pre- and postsynaptic actions within the mouse PAG. This differs to the rat PAG where only μ-opioid receptor actions have been observed

Modulation of Ca2+ channel currents of acutely dissociated rat periaqueductal grey neurons

The actions of the neuropeptide nociceptin on the calcium channel currents (IBa) of acutely dissociated rat periaqueductal grey (PAG) neurons were examined using whole-cell patch clamp techniques. These effects were compared with those of opioid receptor agonists and the GABAB receptor agonist baclofen.Neurons from young adult rats (23 to 56 days old) expressed predominantly ω-conotoxin GVIA (N-type)- and ω-agatoxin IVA (P/Q-type)-sensitive IBa, together with smaller amounts of nimodipine-sensitive current and current resistant to all three blockers. There was proportionately more N-type IBa in neurons from female rats and proportionately more resistant current in neurons from male rats.Nociceptin (EC50, 5 nm) and baclofen (EC50, 0.8 μm) inhibited IBa in all PAG neurons, while the opioid agonist methionine enkephalin (met-enkephalin; 300 nm-10 μm) inhibited IBa in 40 % of neurons. The effects of met-enkephalin were reversed by the μ-opioid antagonist CTAP, and mimicked by the μ-opioid agonist DAMGO (300 nm-3 μm). The δ-opioid agonists DPDPE and deltorphin II, and the κ-opioid agonist U69593, did not affect IBa in any neuron. The actions of nociceptin were not mimicked or blocked by the opioid antagonist naloxone or the nociceptin analogue [desPhe1]-nociceptin.The effects of nociceptin and baclofen on IBa were blocked by pretreatment of the neurons with pertussis toxin (500 ng ml−1, 8 h).Nociceptin predominantly inhibited the N-type (EC50, 2 nm; maximum inhibition, 50 %) and P/Q-type (EC50, 7 nm; maximum inhibition, 33 %) IBa while having little effect on the L-type and R-type IBa.These results are consistent with the previously described actions of nociceptin, baclofen and μ-opioids in PAG slices, whereby they couple to increases in an inwardly rectifying K+ conductance. These agonists thus have the potential to modulate the function of PAG neurons via a number of different cellular effectors