Central bombesin activates adrenal adrenaline- and noradrenaline-containing cells via brain thromboxane A2 in rats.

The sympathetic nervous system regulates peripheral organs via the adrenal chromaffin cells containing adrenaline (A-cells) or noradrenaline (NA-cells) and the sympathetic ganglia. We examined the effect of intracerebroventricularly administered bombesin on neuronal activities of adrenal A-cells and NA-cells and several kinds of sympathetic ganglia (superior cervical, stellate and celiac ganglia) using c-Fos (a marker for neuronal activation), with regard to brain prostanoid, in anesthetized rats. Bombesin induced c-Fos in both adrenal A-cells and NA-cells, but not in any of the sympathetic ganglia. Central pretreatment with either indomethacin (a cyclooxygenase inhibitor) or furegrelate (a thromboxane A(2) synthase inhibitor) abolished all bombesin-induced responses. These results suggest that bombesin centrally activates adrenal A-cells and NA-cells by brain thromboxane A(2)-mediated mechanisms in rats.

Selective activation of the sympathetic ganglia by centrally administered corticotropin-releasing factor in rats.

The sympathetic efferent pathway projects to the sympathetic ganglia and the adrenal medulla. In this study, we examined centrally administered corticotropin-releasing factor (CRF)-induced neuronal activation of noradrenergic postganglionic neurons in several kinds of the sympathetic ganglia (superior cervical, stellate and celiac ganglia) in anesthetized rats. CRF significantly increased c-Fos expression in the celiac and stellate ganglia, with more pronounced effect on the celiac ganglion. On the other hand, CRF had no effect on c-Fos expression in the superior cervical ganglion even at a higher dose. These results suggest that brain CRF selectively regulates neuronal activity of each sympathetic ganglion.

Role of brain prostanoids in glucagon-like peptide-1-induced central activation of sympatho-adrenomedullary outflow in rats.

1. The aim of the present study was to characterize the source of plasma catecholamines induced by centrally administered glucagon-like peptide-1 (GLP-1), with regard to brain prostanoids, in urethane-anaesthetized rats. 2. Glucagon-like peptide-1 and other compounds were administered intracerebroventricularly (i.c.v.) and blood samples were collected via a cannula inserted into the femoral artery. Catecholamines were extracted from plasma with activated alumina and were assayed electrochemically using high-performance liquid chromatography. 3. At 0.3, 1.0 and 3.0 nmol/animal, GLP-1 dose-dependently elevated plasma levels of noradrenaline and adrenaline and the 1.0 nmol GLP-1-induced response was dose-dependently reduced by 5 and 10 nmol/animal exendin (5-39), a selective GLP-1 receptor antagonist. The GLP-1-induced elevation of concentrations of both catecholamines was abolished by 1.2 micromol/animal indomethacin, an inhibitor of cyclo-oxygenase, whereas 1.2 micromol/animal baicalein, a lipoxygenase inhibitor, had no effect. 4. Both furegrelate (1.8 micromol/animal; an inhibitor of thromboxane A(2) synthase) and (+)S-145 (625 nmol/animal; a thromboxane A(2) receptor antagonist) attenuated the GLP-1-induced increases in plasma adrenaline concentrations, but had no effect on the increases in plasma noradrenaline. The GLP-1-induced increase in plasma adrenaline concentrations was abolished by acute bilateral adrenalectomy, but the procedure had no effect on increases in plasma noradrenaline. 5. These results suggest that, in rats, centrally administered GLP-1 induces the secretion of adrenaline from the adrenal medulla by brain thromboxane A(2)-mediated mechanisms, whereas the peptide evokes the release of noradrenaline from sympathetic nerves by brain prostanoids via mechanisms other than those mediated by thromboxane A(2).

Centrally administered N-methyl-d-aspartate evokes the adrenal secretion of noradrenaline and adrenaline by brain thromboxane A2-mediated mechanisms in rats.

Plasma adrenaline mainly originated from adrenaline-containing cells in the adrenal medulla, while plasma noradrenaline reflects the release from sympathetic nerves in addition to the secretion from noradrenaline-containing cells in the adrenal medulla. The present study was undertaken to characterize the source of plasma catecholamines induced by centrally administered N-methyl-d-aspartate with regard to the brain prostanoid, using urethane-anesthetized rats. Intracerebroventricularly (i.c.v.) administered N-methyl-d-aspartate (1.0, 5.0, 10.0 nmol/animal) dose-dependently elevated plasma levels of noradrenaline and adrenaline. The N-methyl-d-aspartate (5.0 nmol/animal, i.c.v.)-induced elevation of both catecholamines was reduced by dizocilpine maleate (5 nmol/animal, i.c.v.), a non-competitive N-methyl-d-aspartate receptor antagonist. Indomethacin (0.6 and 1.2 micromol/animal, i.c.v.), an inhibitor of cyclooxygenase, dose-dependently reduced the N-methyl-d-aspartate (5.0 nmol/animal, i.c.v.)-induced elevation of both catecholamines. The N-methyl-d-aspartate-induced response was dose-dependently attenuated by furegrelate (0.9 and 1.8 micromol/animal, i.c.v.), an inhibitor of thromboxane A2 synthase. Furthermore, the acute bilateral adrenalectomy abolished the N-methyl-d-aspartate-induced responses, indicating that the source of increase in plasma noradrenaline evoked by N-methyl-d-aspartate is due to secretion from the adrenal gland and not due to release from sympathetic nerve terminals. These results suggest that centrally administered N-methyl-d-aspartate induces the secretion of noradrenaline and adrenaline from adrenal medulla by the brain thromboxane A2-mediated mechanisms in rats.

Role of brain nicotinic acetylcholine receptor in centrally administered corticotropin-releasing factor-induced elevation of plasma corticosterone in rats.

The present study was undertaken to clarify the central mechanisms involved in the intracerebroventricularly administered corticotropin-releasing factor-induced elevation of plasma corticosterone in urethane- and alpha-chloralose-anesthetized rats using microdialysis and immunohistochemical techniques. When corticotropin-releasing factor was given at 0.5, 1.5, and 3.0 nmol/animal intracerebroventricularly, it dose-dependently increased noradrenaline release but not adrenaline release in the hypothalamic paraventricular nucleus. The 1.5 nmol/animal dose of corticotropin-releasing factor-induced noradrenaline release was attenuated by CP-154,526 (butyl-ethyl-{2,5-dimethyl-7-(2,4,6 trimethylphenyl)-7H-pyrrolo[2,3-d]pyrimidin-4-yl}amine), a selective corticotropin-releasing factor receptor 1 antagonist, at 1.3 micromol/animal, intracerebroventricularly, and was also abolished by phentolamine at 0.66 micromol/animal, intracerebroventricularly. In addition, the corticotropin-releasing factor-induced elevation of noradrenaline release in the hypothalamic paraventricular nucleus and plasma corticosterone were abolished by hexamethonium, a non-selective nicotinic acetylcholine receptor antagonist, at 1.8 micromol/animal, intracerebroventricularly, and alpha-conotoxin MII, a potent alpha(3)beta(2) nicotinic acetylcholine receptor antagonist, at 30 nmol/animal, i.c.v. Corticotropin-releasing factor at 1.5 nmol/animal, i.c.v. evoked a significant expression of Fos, an immediate-early transcription factor in neurons, on the dopamine-beta-hydroxylase-containing neurons and alpha(3) nicotinic acetylcholine receptor subunit-expressing neurons in the locus coeruleus, but not in the medullary A(1) and A(2) regions containing noradrenergic neurons. These results suggest that centrally administered corticotrophin-releasing factor elevates plasma corticosterone by the corticotropin-releasing factor 1 receptor and alpha(3) subunit-containing nicotinic acetylcholine receptor (probably alpha(3)beta(2) nicotinic acetylcholine receptor) mediated activation of the locus coeruleus noradrenergic neurons projecting to the paraventricular nucleus in rats.

Brain nuclear factor kappa B is involved in the corticotropin-releasing factor-induced central activation of sympatho-adrenomedullary outflow in rats.

Using urethane-anesthetized rats, we examined whether an activation of nuclear factor kappa B is involved in the corticotropin-releasing factor-induced increase in plasma levels of catecholamines. An intracerebroventricularly administered corticotropin-releasing factor (1.5 nmol/animal)-induced increase of plasma catecholamines was dose-dependently reduced by pyrrolidine dithiocarbamate (a nuclear factor kappa B antagonist) (1 and 9 nmol/animal, intracerebroventricularly) and SN50 (a peptide inhibiting nuclear factor kappa B translocation) (9 and 18 nmol/animal, intracerebroventricularly), while SN50M (an inactive control peptide for SN50, 19 nmol/animal, intracerebroventricularly) had no effect on the corticotropin-releasing factor-induced elevation of both catecholamines. Furthermore, the corticotropin-releasing factor-induced responses were also attenuated by rosiglitazone (a peroxisome proliferator-activated receptor-gamma agonist)(50 nmol/animal, intracerebroventricularly). These results suggest the involvement of brain nuclear factor kappa B in the corticotropin-releasing factor-induced central activation of the sympatho-adrenomedullary outflow in rats.

Role of brain adrenoceptors in the corticortopin-releasing factor-induced central activation of sympatho-adrenomedullary outflow in rats.

We investigated the role played by catecholamine-dependent pathways in modulating the ability of centrally administered corticotropin releasing factor (CRF) to activate sympatho-adrenomedullay outflow, using urethane-anesthetized rats. The CRF (1.5 nmol/animal, i.c.v.)-induced elevations of both plasma noradrenaline and adrenaline were attenuated by phentolamine (a non-selective alpha adrenoceptor antagonist) [125 and 250 microg (0.33 and 0.66 micromol)/animal], Heat (a selective alpha(1) adrenoceptor antagonist) [10 and 30 microg (30 and 90 nmol)/animal, i.c.v.] and clonidine (a selective alpha(2) adrenoceptor agonist) [100 microg (0.375 micromol)/animal, i.c.v.]. On the other hand, the CRF (1.5 nmol/animal, i.c.v.)-induced elevation of both catecholamines was not influenced by RS 79948 (a selective alpha(2) adrenoceptor antagonist) [10 and 30 microg (7.2 and 72 nmol)/animal, i.c.v.]. Furthermore, the CRF (1.5 nmol/animal, i.c.v.)-induced elevation of noradrenaline was attenuated by sotalol (a non-selective beta adrenoceptor antagonist) [125 and 250 microg (0.4 and 0.8 micromol)/animal, i.c.v.], while that of adrenaline was not influenced by sotalol. These results suggest that centrally administered CRF-induced elevation of plasma noradrenaline is mediated by an activation of alpha(1) and beta adrenoceptors in the brain, and that of plasma adrenaline is mediated by an activation of alpha(1) adrenoceptors in the brain. Furthermore, central alpha(2) adrenoceptors are involved in modulating the CRF-induced elevation of both plasma catecholamines.

Age-related changes in the expression of ER-beta mRNA in the female rat brain.

Estrogen is important for numerous physiological actions, most of which are mediated via the nuclear estrogen receptors (ERs), ER-alpha and ER-beta, which modulate the transcription of target genes following estrogen binding. Estrogen functions change with age. In the present study, to reveal the effects of normal aging on ER-beta expression in the brain, we examined ER-beta expression at the transcriptional level using young (10 weeks), middle-aged (12 months) and old (24 months) intact female rats. In situ hybridization using a digoxigenin-labeled RNA probe was used to assess the number of ER-beta mRNA-positive cells in each region in whole brain. ER-beta mRNA-positive cells were detected throughout the brain in young female rats and were reduced in number in the olfactory bulb, cerebral cortex, hippocampus, accumbens nucleus, part of the amygdala and raphe nucleus of middle-aged rats but did not decline further in number in aged animals. By contrast, the number of ER-beta mRNA-positive cells in the hippocampus, caudate putamen, claustrum, accumbens nucleus, substantia nigra and cerebellum was not significantly different between young and middle-aged rats but was decreased in old rats. These results indicate that the expression of ER-beta mRNA in the female rat brain is differentially modulated during aging and that the changes are region specific.

Adrenal adrenaline- and noradrenaline-containing cells and celiac sympathetic ganglia are differentially controlled by centrally administered corticotropin-releasing factor and arginine-vasopressin in rats.

The adrenal glands and sympathetic celiac ganglia are innervated mainly by the greater splanchnic nerves, which contain preganglionic sympathetic nerves that originated from the thoracic spinal cord. The adrenal medulla has two separate populations of chromaffin cells, adrenaline-containing cells (A-cells) and noradrenaline-containing cells (NA-cells), which have been shown to be differentially innervated by separate groups of the preganglionic sympathetic neurons. The present study was designed to characterize the centrally activating mechanisms of the adrenal A-cells, NA-cells and celiac sympathetic ganglia with expression of cFos (a marker for neural excitation), in regard to the brain prostanoids, in anesthetized rats. Intracerebroventricularly (i.c.v.) administered corticotropin-releasing factor (CRF) induced cFos expression in the adrenal A-cells, but not NA-cells, and celiac ganglia. On the other hand, i.c.v. administered arginine-vasopressin (AVP) resulted in cFos induction in both A-cells and NA-cells in the adrenal medulla, but not in the celiac ganglia. Intracerebroventricular pretreatment with indomethacin (an inhibitor of cyclooxygenase) abolished the CRF- and AVP-induced cFos expression in all regions described above. On the other hand, intracerebroventricular pretreatment with furegrelate (an inhibitor of thromboxane A2 synthase) abolished the CRF-induced cFos expression in the adrenal A-cells, but not in the celiac ganglia, and also abolished the AVP-induced cFos expression in both A-cells and NA-cells in the adrenal medulla. These results suggest that centrally administered CRF activates adrenal A-cells and celiac sympathetic ganglia by brain thromboxane A2-mediated and other prostanoid than thromboxane A2 (probably prostaglandin E2)-mediated mechanisms, respectively. On the other hand, centrally administered AVP activates adrenal A-cells and NA-cells by brain thromboxane A2-mediated mechanisms in rats.

Brain prostanoid TP receptor-mediated adrenal noradrenaline secretion and EP3 receptor-mediated sympathetic noradrenaline release in rats.

Sympathetic nerves release noradrenaline, whereas adrenal medullary chromaffin cells secrete noradrenaline and adrenaline. Therefore, plasma noradrenaline reflects the secretion from adrenal medulla in addition to the release from sympathetic nerves, however the exact mechanisms of adrenal noradrenaline secretion remain to be elucidated. The present study was designated to characterize the source of plasma noradrenaline induced by intracerebroventricularly (i.c.v.) administered bombesin and prostaglandin E2 in urethane-anesthetized rats. Bombesin (1.0 nmol/animal, i.c.v.) elevated plasma noradrenaline and adrenaline, while prostaglandin E2 (0.3 nmol/animal, i.c.v.) elevated only plasma noradrenaline. The bombesin-induced elevations of both catecholamines were attenuated by pretreatments with furegrelate (an inhibitor of thromboxane A2 synthase) [250 and 500 microg (0.9 and 1.8 micromol)/animal, i.c.v.)] and [(+)-S-145] [(+)-(1R,2R,3S,4S)-(5Z)-7-(3-[4-3H]-phenylsulphonyl-aminobicyclo[2.2.1]hept-2-yl)hept-5-enoic acid sodium salt] (an antagonist of prostanoid TP receptors) [100 and 250 microg (250 and 625 nmol)/animal)], and abolished by acute bilateral adrenalectomy. On the other hand, the prostaglandin E2-induced elevation of plasma noradrenaline was not influenced by acute bilateral adrenalectomy. These results suggest that adrenal noradrenaline secretion and sympathetic noradrenaline release are mediated by differential central mechanisms; brain prostanoid TP receptors activated by bombesin are involved in the adrenal noradrenaline secretion, while brain prostanoid EP (probably EP3) receptors activated by prostaglandin E2 are involved in the sympathetic noradrenaline release in rats. Brain prostanoid TP receptors activated by bombesin are also involved in the adrenal adrenaline secretion.

Brain phospholipase C-diacylglycerol lipase pathway is involved in vasopressin-induced release of noradrenaline and adrenaline from adrenal medulla in rats.

Recently, we reported that intracerebroventricularly (i.c.v.) administered arginine-vasopressin evokes the release of noradrenaline and adrenaline from adrenal medulla by brain thromboxane A2-mediated mechanisms in rats. These results suggest the involvement of brain arachidonic acid in the vasopressin-induced activation of the central adrenomedullary outflow. Arachidonic acid is released mainly by two pathways: phospholipase A2 (PLA2)-dependent pathway; phospholipase C (PLC)- and diacylglycerol lipase-dependent pathway. In the present study, therefore, we attempted to identify which pathway is involved in the vasopressin-induced release of both catecholamines from adrenal medulla using urethane-anesthetized rats. Vasopressin (0.2 nmol/animal, i.c.v.)-induced elevation of plasma noradrenaline and adrenaline was dose-dependently reduced by neomycin [0.28 and 0.55 micromol (250 and 500 microg)/animal, i.c.v.] and 1-[6-[[(17beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione (U-73122) [5 and 10 nmol (2.3 and 4.6 microg)/animal, i.c.v.] (inhibitors of PLC), and also by 1,6-bis(cyclohexyloximinocarbonylamino)hexane (RHC-80267) [1.3 and 2.6 micromol (500 and 1000 microg)/animal, i.c.v.] (an inhibitor of diacylglycerol lipase). On the other hand, mepacrine [1.1 and 2.2 micromol (500 and 1000 microg)/animal, i.c.v.] (an inhibitor of PLA2) was largely ineffective on the vasopressin-induced elevation of plasma catecholamines. These results suggest that vasopressin evokes the release of noradrenaline and adrenaline from adrenal medulla by the brain PLC- and diacylglycerol lipase-dependent mechanisms in rats.