Effects of nicotine on regional blood flow in the olfactory bulb in response to olfactory nerve stimulation.

This study examined the effect of olfactory nerve stimulation on regional cerebral blood flow and assessed the effect of intravenous nicotine administration on this response in anesthetized rats. Regional cerebral blood flow was measured with laser Doppler flowmetry or laser speckle contrast imaging. Unilateral olfactory nerve stimulation for 5 s produced current (≥ 100 µA) and frequency-dependent (≥ 5 Hz) increases in blood flow in the olfactory bulb ipsilateral to the stimulus. The increased olfactory bulb blood flow peaked at 30 ± 7% using stimulus parameters of 300 µA and 20 Hz. Nerve stimulation did not change frontal cortical blood flow or mean arterial pressure. The intravenous injection of nicotine (30 µg/kg) augmented the olfactory bulb blood flow response to nerve stimulation (20 Hz, 300 µA) by approximately 1.5-fold (60-s area after the stimulation). These results indicate that olfactory nerve stimulation increases olfactory bulb blood flow, and the response is potentiated by the activation of nicotinic cholinergic transmission.

Effect of quercetin on plasma extravasation in rat CNS and dura mater by ACE and NEP inhibition.

The effects of quercetin on substance P-induced plasma protein extravasation (PE) in the rat dura mater, cerebellum, olfactory bulb and cortex and also its modulation by endopeptidases, angiotensin-converting enzyme (ACE) and neutral endopeptidase (NEP) were studied. PE was assessed by photometric measurement of extravasated Evans blue. Substance P (SP) and NEP or ACE inhibitors increased the PE in dura mater. Pretreatment with captopril or phosphoramidon potentiated PE induced by SP in the dura mater and cerebellum, respectively. Quercetin increased the PE in the dura mater, cerebellum and cortex. Further results suggested that the PE induced by SP in the dura mater was enhanced by pretreatment with quercetin, similar to that observed with selective peptidase inhibitors. Quercetin-stimulated extravasation in all tissues was abolished by NK-1 receptor blockade. These results suggest that quercetin increases PE in the dura mater and CNS tissues by inhibiting NEP and/or ACE, showing that the effect induced in the dura mater, cerebellum and cortex occurs through endogenous SP accumulation.

Cellular localization of vasopressin V1a receptor messenger ribonucleic acid in adult male rat brain, pineal, and brain vasculature.

Vasopressin V1a receptor (V1aR) transcripts were localized in brain, pineal, and superficial brain vascular tissues of adult male rats using hybridization histochemistry and an [35S]riboprobe complementary to the messenger ribonucleic acid (mRNA) encoding the fifth to the midseventh transmembrane regions of the receptor. V1aR mRNA was extensively distributed throughout brain and was expressed in 1) superficial cells of the granule cell layers of the main olfactory bulb, hippocampal dentate gyrus, and cerebellum; 2) numerous anatomically distinct brain nuclei; 3) isolated cells dispersed throughout the central nervous system; 4) cells of the choroid plexus, occasional blood vessels in the olfactory bulb and interpeduncular nucleus, and extraparenchymal intracranial vasculature; and 5) some white matter structures. Numerous cells expressing V1aR transcripts were found in forebrain structures, including primary olfactory (piriform) cortex, the anterior and posterior olfactory nuclei; dorsal, intermediate, and ventral lateral septal nuclei; the septo-fimbrial nucleus and accumbens nucleus; and numerous hypothalamic regions with the most intense hypothalamic labeling in the arcuate, stigmoid, suprachiasmatic, and periventricular nuclei and the lateral hypothalamic area. Cells expressing V1aR transcripts were ubiquitous throughout the midbrain, pontine, and medullary regions. A lower intensity signal was found in cells of the parvocellular paraventricular and anteroventral nucleus of the thalamus, circumventricular organs including the pineal, and the subfornical organ. V1aR transcripts were not generally detected in parenchymal vasculature, but could be found over large blood vessels in the interpeduncular nucleus and medial olfactory bulb; transcripts were commonly detected in perivascular brain cells. V1aR mRNA was abundantly expressed by choroid plexus, endothelial cells of midline blood vessels between the main olfactory bulbs, and superficial vascular tissue on all brain surfaces. These data confirm the presence of the vascular/hepatic-type V1aR gene in brain tissue and document an extensive expression. The distribution of V1aR mRNA suggests that there are at least two types of vasopressin-responsive cells in brain: one type exemplified by lateral septal ara neurons innervated by classical axodendritic/somatic synaptic vasopressinergic terminals and a second, perivascular/vascular type that would facilitate humoral vasopressinergic signaling in the brain.

[Measurement of the blood flow in various areas of the rat brain by means of microspheres]. / Mesure du flux sanguin dans les différentes régions du cerveau du rat au moyen de microsphères

A method is described to measure regional blood flow in different structures of the rat brain. Microspheres (15 micron) are injected, the brain is sectioned, stained for myeline, radioautographs are prepared and the microspheres in the different structures are counted. The values obtained for different brain structures are counted. The values obtained for different brain regions (cortex, corpus callosum, thalamus hipocampus, hypothalamic region, colliculi, cerebellum, pons, medulla) compare well with those published by others on larger animals. In rats fed 1% of lead from birth, higher blood flow is found in the cortex and a lower one in the interior part of the brain compared to controls.