Effects of hyperinsulinemia on local cerebral insulin binding and glucose utilization in normoglycemic awake rats.

The present study was carried out to characterize the effects of insulin, using the euglycemic hyperinsulinemic clamp, on insulin binding and glucose utilization in specific areas of rat brain, by autoradiographic methods. Binding of [125I]Insulin was significantly higher in the hippocampus CA1, the ventromedial and lateral hypothalamus nuclei of the hyperinsulinemic rats than in control rats. Glucose utilization was slightly but not significantly decreased in the hippocampus CA1, the ventromedial and lateral hypothalamus of hyperinsulinemic rats.

Metabolic clearance of insulin from the cerebrospinal fluid in the anesthetized rat.

Infusion of 125I-(Tyr A14)-insulin at tracer doses into the cerebrospinal fluid (CSF) resulted in a slow rate of increase in the CSF-labeled insulin during the first 2 hours with a plateau thereafter. Labeled insulin was cleared from the CSF at a higher rate than 3H-inulin, a marker of CSF bulk flow. The labeled insulin was mainly distributed in all the ventricular and periventricular brain regions.

Postsynaptic receptors for cholecystokinin in the thalamic reticular nucleus: a possible modulatory system for sensory transmission.

Cholecystokinin (CCK) binding sites have been described in several areas of the brain with a particularly rich localization being found in the thalamic reticular nucleus (TRN). We have studied the distribution of CCK binding sites in the TRN using a high resolution autoradiographic technique and observed that the CCK receptors were dense throughout the whole nucleus. Using kainic acid excitotoxic lesions, it was demonstrated that CCK receptors were attached to postsynaptic elements and not to afferent fibers.

Autoradiography of CCK receptors in the rat brain using [(3)H]Boc[Nle(28)(31)]CCK(27)-(33) and [(125)I]bolton-hunter CCK(8). Functional significance of subregional distributions.

[(3)H]Boc[Nle(28,31)]CCK(27)-(33) ([(3)H]BDNL-CCK(7)) is a new ligand for cholecystokinin (CCK) receptors, endowed with a high specific activity (100 Ci/mmol). Binding sites for this ligand were visualized in the rat brain by autoradiography [(3)H]BDNL-CCK(7) binds specifically to an apparent single class of CCK receptors on rat striatum sections with a K(d) of 1.76 nM and a B(max) of 57 fmol/mg protein.

[Radioautographic and quantitative study of insulin binding sites in the rat brain].

In the present study, we describe the specificity and the autoradiographic distribution of insulin binding sites in the rat central nervous system (CNS) after in vitro incubation of brain sections with [125I]-14A insulin. Increasing concentrations of unlabeled insulin produced a dose-dependent inhibition of [125I]-insulin binding which represented 92 +/- 2% displacement with 3 X 10(-5) M, whatever the brain sections tested. Half-maximum inhibition with native insulin was obtained with 2.