Comparison of histamine-H(1) receptors in bovine intracerebral microvessels with cerebral grey matter by [(3)H]mepyramine binding.

Abstract

Small intracerebral blood vessels (microvessels) of bovine brain are known to contain the vasoactive amine histamine, and the presence of histamine-H(1) receptors in microvessels was examined using the radioligand, [(3)H]mepyramine. Microvessels were isolated from cerebral cortex grey matter, striatum and hippocampus by a sieving technique and membranes prepared for binding studies. [(3)H]Mepyramine bound to a single, high affinity site, which displayed stereoselectivity for (+) chlorpheniramine relative to its (?) isomer and was consistent with binding to H(1)-receptors. The density of binding sites (B(max)), in microvessel membranes from cortical grey matter, was approximately one-third of that seen in membranes prepared from cortical grey matter. Microvessels isolated from striata and hippocampi had a similar density of H(1)-receptor sites to that seen in cortical microvessels. These results demonstrate that bovine intracerebral microvessels contain significant numbers of histamine-H(1) receptors and strengthen the hypothesis that histamine could regulate the calibre of intracerebral blood vessels.