TY - JOUR
T1 - Midline thalamic paraventricular nucleus neurons display diurnal variation in resting membrane potentials, conductances, and firing patterns in vitro
AU - Kolaj, Miloslav
AU - Zhang, Li
AU - Rønnekleiv, Oline K.
AU - Renaud, Leo P.
PY - 2012/4/1
Y1 - 2012/4/1
N2 - Neurons in the rodent midline thalamic paraventricular nucleus (PVT) receive inputs from brain stem and hypothalamic sites known to participate in sleep-wake and circadian rhythms. To evaluate possible diurnal changes in their excitability, we used patch-clamp techniques to record and examine the properties of neurons in anterior PVT (aPVT) in coronal rat brain slices prepared at zeitgeber time (ZT) 2-6 vs. ZT 14-18 and recorded at ZT 8.4 ± 0.2 (day) vs. ZT 21.2 ±0.2 (night), the subjective quiet vs. aroused states, respectively. Compared with neurons recorded during the day, neurons from the night period were significantly more depolarized and exhibited a lower membrane conductance that in part reflected loss of a potassium-mediated conductance. Furthermore, these neurons were also significantly more active, with tonic and burst firing patterns. Neurons from each ZT period were assessed for amplitudes of two conduct ances known to contribute to bursting behavior, i.e., low-threshold-activated Ca 2+ currents (I T) and hyper polarization- activated cation currents (I h). Data revealed that amplitudes of both I T and I h were significantly larger during the night period. In addition, biopsy samples from the night period revealed a significant increase in mRNA for Ca v3.1 and Ca v3.3 low-threshold Ca 2+ channel subtypes. Neurons recorded from the night period also displayed a comparative enhancement in spontaneous bursting at membrane potentials of approximately -60 mV and in burst firing consequent to hyper polarization-induced low-threshold currents and depolarization-induced current pulses. These novel in vitro observations reveal that midline thalamic neurons undergo diurnal changes in their I T, I h, and undefined potassium conductances. The underlying mechanisms remain to be characterized.
AB - Neurons in the rodent midline thalamic paraventricular nucleus (PVT) receive inputs from brain stem and hypothalamic sites known to participate in sleep-wake and circadian rhythms. To evaluate possible diurnal changes in their excitability, we used patch-clamp techniques to record and examine the properties of neurons in anterior PVT (aPVT) in coronal rat brain slices prepared at zeitgeber time (ZT) 2-6 vs. ZT 14-18 and recorded at ZT 8.4 ± 0.2 (day) vs. ZT 21.2 ±0.2 (night), the subjective quiet vs. aroused states, respectively. Compared with neurons recorded during the day, neurons from the night period were significantly more depolarized and exhibited a lower membrane conductance that in part reflected loss of a potassium-mediated conductance. Furthermore, these neurons were also significantly more active, with tonic and burst firing patterns. Neurons from each ZT period were assessed for amplitudes of two conduct ances known to contribute to bursting behavior, i.e., low-threshold-activated Ca 2+ currents (I T) and hyper polarization- activated cation currents (I h). Data revealed that amplitudes of both I T and I h were significantly larger during the night period. In addition, biopsy samples from the night period revealed a significant increase in mRNA for Ca v3.1 and Ca v3.3 low-threshold Ca 2+ channel subtypes. Neurons recorded from the night period also displayed a comparative enhancement in spontaneous bursting at membrane potentials of approximately -60 mV and in burst firing consequent to hyper polarization-induced low-threshold currents and depolarization-induced current pulses. These novel in vitro observations reveal that midline thalamic neurons undergo diurnal changes in their I T, I h, and undefined potassium conductances. The underlying mechanisms remain to be characterized.
KW - Brain slice preparations
KW - Burst firing patterns
KW - Day-night
KW - Midline thalamus
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U2 - 10.1152/jn.00974.2011
DO - 10.1152/jn.00974.2011
M3 - Article
C2 - 22219029
AN - SCOPUS:84859518734
SN - 0022-3077
VL - 107
SP - 1835
EP - 1844
JO - Journal of neurophysiology
JF - Journal of neurophysiology
IS - 7
ER -