Physiological and molecular characteristics of rat hypothalamic ventromedial nucleus glucosensing neurons.
To evaluate potential mechanisms for neuronal glucosensing, fura-2 Ca(2+) imaging and single-cell RT-PCR were carried out in dissociated ventromedial hypothalamic nucleus (VMN) neurons. Glucose-excited (GE) neurons increased and glucose-inhibited (GI) neurons decreased intracellular Ca(2+) ([Ca(2+)](i)) oscillations as glucose increased from 0.5 to 2.5 mmol/l. The Kir6.2 subunit mRNA of the ATP-sensitive K(+) channel was expressed in 42% of GE and GI neurons, but only 15% of nonglucosensing (NG) neurons. Glucokinase (GK), the putative glucosensing gatekeeper, was expressed in 64% of GE, 43% of GI, but only 8% of NG neurons and the GK inhibitor alloxan altered [Ca(2+)](i) oscillations in approximately 75% of GK-expressing GE and GI neurons. Insulin receptor and GLUT4 mRNAs were coexpressed in 75% of GE, 60% of GI, and 40% of NG neurons, although there were no statistically significant intergroup differences. Hexokinase-I, GLUT3, and lactate dehydrogenase-A and -B were ubiquitous, whereas GLUT2, monocarboxylate transporters-1 and -2, and leptin receptor and GAD mRNAs were expressed less frequently and without apparent relationship to glucosensing capacity. Thus, although GK may mediate glucosensing in up to 60% of VMN neurons, other regulatory mechanisms are likely to control glucosensing in the remaining ones.
Kang
Ling
L
Department of Neurology and Neurosciences, New Jersey Medical School, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, USA.
Routh
Vanessa H
VH
Kuzhikandathil
Eldo V
EV
Gaspers
Larry D
LD
Levin
Barry E
BE
D000818:Animals; D019540:Area Under Curve; D001483:Base Sequence; D002118:Calcium / Q000378:metabolism / Q000502:physiology*; D017931:DNA Primers; D005941:Glucokinase / Q000235:genetics; D005947:Glucose / Q000502:physiology*; D007700:Kinetics; D008297:Male; D009004:Monosaccharide Transport Proteins / Q000235:genetics; D009474:Neurons / Q000502:physiology*; D051381:Rats; D011930:Reaction Time; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014697:Ventromedial Hypothalamic Nucleus / Q000502:physiology*
D017931:DNA Primers; D009004:Monosaccharide Transport Proteins; D005941:Glucokinase; D005947:Glucose; D002118:Calcium