Abstract
Pharmacological stimulation/antagonism of astrocyte glio-peptide octadecaneuropeptide signaling alters ventromedial hypothalamic nucleus (VMN) counterregulatory γ-aminobutyric acid (GABA) and nitric oxide transmission. The current research used newly developed capillary zone electrophoresis-mass spectrometry methods to investigate hypoglycemia effects on VMN octadecaneuropeptide content, along with gene knockdown tools to determine if octadecaneuropeptide signaling regulates these transmitters during eu- and/or hypoglycemia. Hypoglycemia caused dissimilar adjustments in the octadecaneuropeptide precursor, i.e., diazepam-binding-inhibitor and octadecaneuropeptide levels in dorsomedial versus ventrolateral VMN. Intra-VMN diazepam-binding-inhibitor siRNA administration decreased baseline 67 and 65 kDa glutamate decarboxylase mRNA levels in GABAergic neurons laser-microdissected from each location, but only affected hypoglycemic transcript expression in ventrolateral VMN. This knockdown therapy imposed dissimilar effects on eu- and hypoglycemic glucokinase and 5'-AMP-activated protein kinase-alpha1 (AMPKα1) and -alpha2 (AMPKα2) gene profiles in dorsomedial versus ventrolateral GABAergic neurons. Diazepam-binding-inhibitor gene silencing up-regulated baseline (dorsomedial) or hypoglycemic (ventrolateral) nitrergic neuron neuronal nitric oxide synthase mRNA profiles. Baseline nitrergic cell glucokinase mRNA was up- (ventrolateral) or down- (dorsomedial) regulated by diazepam-binding-inhibitor siRNA, but knockdown enhanced hypoglycemic profiles in both sites. Nitrergic nerve cell AMPKα1 and -α2 transcripts exhibited division-specific responses to this genetic manipulation during eu- and hypoglycemia. Results document the utility of capillary zone electrophoresis-mass spectrometric tools for quantification of ODN in small-volume brain tissue samples. Data show that hypoglycemia has dissimilar effects on ODN signaling in the two major neuroanatomical divisions of the VMN and that this glio-peptide imposes differential control of glucose-regulatory neurotransmission in the VMNdm versus VMNvl during eu- and hypoglycemia.