Journal: Scientific Reports

Article Title: Chronic antidepressant potentiates spontaneous activity of dorsal raphe serotonergic neurons by decreasing GABA B receptor-mediated inhibition of L-type calcium channels

doi: 10.1038/s41598-017-13599-3

Figure Lengend Snippet: L-type voltage-dependent Ca 2+ channel (VDCC) participates in the spontaneous activity of DRN serotonergic neurons. ( a ) Representative traces of the spontaneous firing before (left) and after (right) the application of BAY K 8644 (BAY K; 1 μM). ( b ) The effect of BAY K 8644 (BAY K; 1 μM) on the spontaneous firing rate in serotonergic neurons. The average firing rate between 150–180 s after beginning the perfusion was compared to the basal firing rate (right). * P < 0.05 vs . Control. (Control, n = 4 neurons from 2 mice; BAY K, n = 6 neurons from 3 mice; P = 0.0496, Student’s t -test). ( c ) To block L-type VDCC current only in the recorded neurons, D890 (0.5 mM) was added to pipette solution, and the spontaneous firing was recorded for 30 s both in cell-attached (left) and whole-cell (right) configurations. ( d ) The average firing rate between 60–90 s after beginning the whole-cell recordings was compared to that in the cell-attached recordings. * P < 0.05 vs . Control. (Control, n = 4 neurons from 3 mice; D890, n = 4 neurons from 3 mice; P = 0.0190, Student’s t -test). Data are presented as the mean ± S.E.M.

Article Snippet: 6,7-dinitroquinoxaline-2,3(1 H,4 H)-dione (DNQX; an AMPA (non-NMDA) antagonist; Tocris Bioscience, Bristol, UK), bicuculline (a selective GABA A antagonist; Enzo Life Science, Farmingdale, NY, USA), prazosin (an α 1 receptor antagonist; Sigma-Aldrich), ZD7288 (a selective hyperpolarization-activated cyclic nucleotide–gated channel blocker; Cayman Chemical Company, Ann Arbor, MI, USA), (S)-(-)-Bay K 8644 (Bay K 8644; an L-type voltage-dependent Ca 2+ channel (VDCC) activator; Santa Cruz Biotechnology, Santa Cruz, CA, USA), nifedipine (an L-type VDCC blocker; Wako Pure Chemical Industries, Osaka, Japan), KT5720 (a selective PKA inhibitor; Wako Pure Chemical Industries), and gallein (a selective G βγ inhibitor; Sigma-Aldrich) were dissolved in dimethyl sulfoxide (DMSO).

Techniques: Activity Assay, Control, Blocking Assay, Transferring

Journal: Scientific Reports

Article Title: Chronic antidepressant potentiates spontaneous activity of dorsal raphe serotonergic neurons by decreasing GABA B receptor-mediated inhibition of L-type calcium channels

doi: 10.1038/s41598-017-13599-3

Figure Lengend Snippet: Chronic administration of citalopram increased L-type VDCC current. ( a ) Outline of recordings from citalopram-administrated mice. After chronic treatment with citalopram (Cit; 24 mg/kg/day) or its vehicle (Water) for 28 days, acute raphe slices were prepared, and whole-cell voltage clamp recordings were performed. ( b ) Representative traces (left) and peak current (right) of high voltage activated (HVA) current in DRN serotonergic neurons from drug-naïve (Water) and citalopram-treated (Cit) mice. * P < 0.05 vs . Water. (Water, n = 8 neurons from 3 mice; Cit, n = 9 neurons from 4 mice; Student’s t -test; P = 0.0487). ( c ) Effects of intracellularly applied D890 on HVA current in DRN serotonergic neurons. P = 0.3402 vs . Water by Student’s t -test, Water, n = 8 neurons from 2 mice; Cit, n = 8 neurons from 2 mice. ( d ) Effects of bath-applied CGP52432 on high voltage activated (HVA) current in DRN serotonergic neurons. P = 0.5283 vs . Water by Student’s t -test, Water, n = 14 neurons from 4 mice; Cit, n = 11 neurons from 2 mice. ( e ) HVA VDCC current was recorded in the presence of WAY100635 and GR127935. * P < 0.05 vs . Water. (Water, n = 11 neurons from 2 mice; Cit, n = 12 neurons from 2 mice; Student’s t -test; P = 0.0107). ( f ) Effects of intracellularly applied KT5720 on HVA current in DRN serotonergic neurons. P = 0.6866 vs . Water by Student’s t -test, Water, n = 10 neurons from 2 mice; Cit, n = 12 neurons from 2 mice. ( g ) Effects of intracellularly applied gallein (20 μM) on HVA current in DRN serotonergic neurons. * P < 0.05 vs . Water. (Water, n = 12 neurons from 2 mice; Cit, n = 17 neurons from 2 mice; Student’s t -test; P = 0.0172). Data are presented as the mean ± S.E.M. ( h ) In normal condition, continuous GABA B receptor signaling inhibits PKA activation. Decreased PKA activity might cause inhibition of L-type VDCC activity and subsequently serotonergic firing activity. After chronic antidepressant treatment, postsynaptic GABA B signaling is decreased, resulting in activation of PKA and disinhibition of L-type VDCCs. Increasing Ca 2+ current through L-type VDCCs accelerates serotonergic firing activity.

Article Snippet: 6,7-dinitroquinoxaline-2,3(1 H,4 H)-dione (DNQX; an AMPA (non-NMDA) antagonist; Tocris Bioscience, Bristol, UK), bicuculline (a selective GABA A antagonist; Enzo Life Science, Farmingdale, NY, USA), prazosin (an α 1 receptor antagonist; Sigma-Aldrich), ZD7288 (a selective hyperpolarization-activated cyclic nucleotide–gated channel blocker; Cayman Chemical Company, Ann Arbor, MI, USA), (S)-(-)-Bay K 8644 (Bay K 8644; an L-type voltage-dependent Ca 2+ channel (VDCC) activator; Santa Cruz Biotechnology, Santa Cruz, CA, USA), nifedipine (an L-type VDCC blocker; Wako Pure Chemical Industries, Osaka, Japan), KT5720 (a selective PKA inhibitor; Wako Pure Chemical Industries), and gallein (a selective G βγ inhibitor; Sigma-Aldrich) were dissolved in dimethyl sulfoxide (DMSO).

Techniques: Activation Assay, Activity Assay, Inhibition

Journal:

Article Title: Contractile activity in intestinal muscle evokes action potential discharge in guinea-pig myenteric neurons

doi: 10.1111/j.1469-7793.1999.0547t.x

Figure Lengend Snippet: Aa, record from a Dogiel type II neuron in tissue that was pinned without stretch and not exposed to drug; no action potentials were recorded. Ab, record from the same neuron after the addition of (-)-Bay K 8644 (1 μm), showing maintained action potential firing. Ba, membrane activity in a Dogiel type I neuron in tissue that was unstretched. Small depolarizing potentials with time courses similar to fast EPSPs were observed, but the neuron did not fire action potentials. Bb, response of the neuron to a depolarizing current pulse, indicating that it was excitable although it did not fire action potentials spontaneously prior to the addition of (-)-Bay K 8644. Bc, action potential firing after the addition of (-)-Bay K 8644. Bd, action potential discharge in the presence of (-)-Bay K 8644 was abolished when the membrane was hyperpolarized in response to current passed through the recording electrode, during the period that is marked.

Article Snippet: Tissue was contracted using the L-type channel opener (-)-Bay K 8644 (1 μ m ) (Research Biochemicals International).

Techniques: Activity Assay

Journal:

Article Title: Contractile activity in intestinal muscle evokes action potential discharge in guinea-pig myenteric neurons

doi: 10.1111/j.1469-7793.1999.0547t.x

Figure Lengend Snippet: Aa, action potential firing while the tissue was stretched 40% beyond slack width, but not exposed to drug; membrane potential -55 mV. Ab, membrane potential record taken from the same neuron 5 min after exposure of the tissue to gadolinium (1 μm); membrane potential -58 mV. Although no spontaneous action potentials were recorded in this period, the cell was sufficiently excitable to respond with anode break action potentials following a hyperpolarizing current pulse. Ac, interval return map for this neuron, before the addition of Gd3+. The map shows that the neuron exhibited a mixture of bursting and irregular action potential discharge. Ba, spontaneous action potential discharge in a second neuron after Bay K 8644 (1 μm) was added in the presence of Gd3+. Despite the presence of Gd3+, contraction evoked by Bay K 8644 was accompanied by action potentials in Dogiel type II neurons. Bb, record from the same neuron after exposure of the tissue to dispase (1 mg ml−1). This abolished the action potentials in the neuron, although the muscle continued to contract. An intracellular current pulse, at the dot, evoked a full action potential, indicating that the cell had not lost its ability to be excited.

Article Snippet: Tissue was contracted using the L-type channel opener (-)-Bay K 8644 (1 μ m ) (Research Biochemicals International).

Techniques: