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