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PubMed1981

Acute sino-aortic denervation in rats produces a selective increase of adrenaline turnover in the dorsal midline area of the caudal medulla oblongata and a reduction of adrenaline levels in the anterior and posterior hypothalamus.

Acute sino-aortic denervation produces an acute reduction of adrenaline stores in the anterior and posterior hypothalamus and a reduction of noradrenaline stores in the dorsal midline area of the caudal medulla oblongata. Furthermore, removal of baroreflex afferents results in an increase of adrenaline turnover in the DCMO but not in the hypothalamus. The present findings give evidence for participation of adrenergic mechanisms in central baroreflex regulation. The findings can be interpreted according to the adrenaline vasodepressor hypothesis of hypertension.

Animals↗
PubMed2006

Hemorrhage activates proopiomelanocortin neurons in the rat hypothalamus.

Severe blood loss lowers arterial pressure through a central mechanism that is thought to include opioid neurons. In this study, we investigated whether hemorrhage activates proopiomelanocortin (POMC) neurons by measuring Fos immunoreactivity and POMC mRNA levels in the medial basal hypothalamus. Hemorrhage (2.2 ml/100 g body weight over 20 min) increased the number of Fos immunoreactive neurons throughout the rostral-caudal extent of the arcuate nucleus, the retrochiasmatic area and the peri-arcuate region lateral to the arcuate nucleus where POMC neurons are located. Double label immunohistochemistry revealed that hemorrhage increased Fos expression by beta-endorphin immunoreactive neurons significantly. The proportion of beta-endorphin immunoreactive neurons that expressed Fos immunoreactivity increased approximately four-fold, from 11.7+/-1.4% in sham-operated control animals to 42.0+/-5.2% in hemorrhaged animals. Hemorrhage also increased POMC mRNA levels in the medial basal hypothalamus significantly, consistent with the hypothesis that blood loss activates POMC neurons. To test whether activation of arcuate neurons contributes to the fall in arterial pressure evoked by hemorrhage, we inhibited neuronal activity in the caudal arcuate nucleus by microinjecting the local anesthetic lidocaine (2%; 0.1 or 0.3 microl) bilaterally 2 min before hemorrhage was initiated. Lidocaine injection inhibited hemorrhagic hypotension and bradycardia significantly although it did not influence arterial pressure or heart rate in non-hemorrhaged rats. These results demonstrate that hemorrhage activates POMC neurons and provide evidence that activation of neurons in the arcuate nucleus plays an important role in the hemodynamic response to hemorrhage.

Animals↗
PubMed2001

Regional distribution of benzodiazepine binding sites in the human newborn and infant hypothalamus. A quantitative autoradiographic study.

Using in vitro quantitative autoradiography and [3H]flunitrazepam we examined the rostrocaudal distribution of benzodiazepine binding sites in the human neonate/infant hypothalamus. The autoradiographic analysis shows the presence of a heterogeneous distribution throughout the rostrocaudal extent of this brain structure. High [3H]flunitrazepam binding corresponds primarily to the diagonal band of Broca and the preoptic region. The labelling in the preoptic region showed a rostrocaudal increase, contrasting in that with the other hypothalamic structures. Intermediate densities were present in the septohypothalamic, suprachiasmatic, periventricular and paraventricular nuclei as well as in the mammillary complex. Low binding was observed in the other hypothalamic structures. The benzodiazepine binding sites analyzed belong mostly to type II receptors. In an attempt to unravel possible differences related to age, we compared the autoradiographic distribution in three postnatal age ranges. The topographical distribution of these binding sites was almost identical in each period analyzed. We found, however, that benzodiazepine binding is generally low in the neonatal period and a tendency in increasing densities is observed during development. Taken together, these results provide evidence for a large distribution of benzodiazepine binding sites in neonate/infant hypothalamus, suggesting their implication in the development of this brain structure and the maintenance of its various functions.

Age Factors↗
PubMed1998

Aromatic L-amino acid decarboxylase- and tyrosine hydroxylase-immunohistochemistry in the adult human hypothalamus.

The distribution of cell bodies immunoreactive for tyrosine hydroxylase and aromatic L-amino acid decarboxylase was studied in the adult human hypothalamus. Many neurons in the posterior (A11) and caudal dorsal hypothalamic areas (A13) as well as in the arcuate (A12) and periventricular (A14) zone were immunoreactive for the two enzymes, suggesting that they were dopaminergic. Numerous tyrosine hydroxylase-immunoreactive neurons, which were not immunoreactive for aromatic L-amino acid decarboxylase, could be seen in the paraventricular, supraoptic and accessory nuclei (A15) as well as in the rostral dorsal hypothalamic area. These were considered to be non-dopaminergic. Conversely, large numbers of small neurons immunoreactive for aromatic L-amino acid decarboxylase but not for tyrosine hydroxylase, were identified in the premammillary nucleus (D8), zona incerta (D10), lateral hypothalamic area (D11), anterior portion of the dorsomedial nucleus (D12), suprachiasmatic nucleus (D13), medial preoptic area and bed nucleus of the stria terminalis (D14). In the human hypothalamus, besides dopaminergic cell bodies, there exists a large number of tyrosine hydroxylase-only and aromatic L-amino acid decarboxylase-only neurons, whose physiological roles remain to be determined.

Aged↗
PubMed1977

The distribution of arylamidases in the hypothalamus of rat and the effect of exogenous testosterone.

Arylamidase activities towards specific substrates, the 4-nitroanilides of L-alanine, L-leucine, L-phenylanine, L-tyrosinb L-cystine, L-glutamic acid, and L-glycine, have been investigated in different regions of the hypothalamus of adult, male rat. It was found that the activities with respect to these substrates decreased in the order listed above, in all tissues examined. The arylamidase activity towards L-alamine-4-nitroanilide and L-cystine-bis(4-mitroanilide) was elevated in hypothalamic tissues as compared to the cerebral cortex, but the relatives distribution of the activity towards these two substrates varied in different regions of the hypothalamus. Testosterone caused a decrease in the level of arylamidase activity towards the cystine substrate in all hypothalamic regions, an effect which was found to be dose dependent. The role of hypothalamic arylamidases is discussed.

Amino Acids↗
PubMed1977

Quantitative histochemical studies of the hypothalamus: dehydrogenase enzymes following androgen sterilization.

Four enzymes, selected as representative of major metabolic pathways (malic dehydrogenase, of the citric acid cycle, lactic dehydrogenase, of glycolysis, glucose-6-phosphate dehydrogenase, of the pentose pathway and glutamic dehydrogenase, of glutamate metabolism), were measured by quantitative histochemical methods in individual hypothalamic nuclei of adult neonatally androgenized female rats. Malic dehydrogenase (MDH) was significantly reduced in nuclei of the anterior hypothalamus: the suprachiasmatic, supraoptic and anterior. Lactic dehydrogenase (LDH) increased significantly in the lateral preoptic area. Glucose-6-phosphate dehydrogenase G-6-PDH was also significantly elevated in anterior hypothalamic nuclei: medial preoptic, lateral preoptic, supraoptic and paraventricular. Glutamic dehydrogenase (GDH) was generally elevated throughout the hypothalamus with significant increases of activity occurring in the paraventricular, lateral ventromedial, arcuate, medial mamillary and posterior nuclei.

Animals↗
PubMed1990

A norepinephrine-dependent mechanism in the preoptic/anterior hypothalamic area but not in the mediobasal hypothalamus is involved in the regulation of the gonadotropin-releasing hormone pulse generator in ovariectomized rats.

Pulsatile gonadotropin secretion from the pituitary is dependent upon the gonadotropin-releasing hormone (Gn-RH) pulse generator producing intermittent release of the neuropeptide into the portal vessels. Various neurotransmitters seem to be involved in the regulation of pulsatile Gn-RH release. The present study was an attempt to determine in vivo the temporal relation of preoptic/anterior hypothalamic area (PO/AH) norepinephrine (NE) release and pulsatile luteinizing hormone (LH) secretion in ovariectomized rats. To assess whether NE acts in the PO/AH to maintain pulsatile Gn-RH release, we applied locally an alpha 1-receptor antagonist into this structure. Push-pull cannulae (PPC) were implanted into the PO/AH of ovariectomized rats. The contralateral, not PPC-implanted PO/AH was lesioned electrochemically. Another group of ovariectomized rats was implanted with a PPC into the mediobasal hypothalamus. Two experiments were performed: (1) To determine whether the PO/AH or the mediobasal hypothalamus is the site where NE exerts its stimulatory effect on LH secretion, we applied doxazosine, a new specific alpha 1-receptor antagonist, locally into these structures by means of PPC. The effect of this adrenergic drug on the Gn-RH pulse generator was examined by measuring blood LH levels. (2) To study the temporal relation between in vivo release rates of NE and amine metabolites in the preoptic area and pulsatile pituitary LH secretion, preoptic perfusates and blood samples were collected at 5-min intervals. Brain perfusates were subjected to high-performance liquid chromatography-electrochemical analysis. In blood samples LH concentrations were determined.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗
PubMed1995

Glutamate and GABAergic neurointeractions in the monkey hypothalamus: a quantitative immunomorphological study.

Glutamate (Glu) and gamma-aminobutyric acid (GABA) are the most abundant excitatory and inhibitory neurotransmitters in the mammalian hypothalamus. Glu and GABA-containing neurons have both been shown to synapse with gonadotropin-releasing hormone (GnRH) and other neuroendocrine systems in the hypothalamus of several species. Since their direct interactions could play a pivotal role in governing neuroendocrine function, we performed double-label immunostaining for Glu and for glutamic acid decarboxylase (GAD) as a marker for GABAergic neurons in hypothalamic sections from adult female cynomolgus monkeys. Ultrastructural analysis of 785 Glu-immunoreactive (-ir) and GAD-ir elements in the medial septum (MS), arcuate nucleus-ventral hypothalamic tract (VHT1), supraoptic nucleus (SON), paraventricular nucleus (PVN), and median eminence (ME) revealed that 63% were Glu-ir, 28% were GAD-ir, and 9% were Glu + GAD-ir. In addition, we observed surprisingly consistent labeling of 2-4% somata (SOM), 65-80% dendrites (DEN), and 15-30% axons and terminals (AXO) in all of these areas. Characterization of 177 interactions (36% synapses, 64% contacts) by pre/post-transmitter content indicated that 29% contained Glu/GAD, 15% Glu/Glu, and 15% Glu/Glu + GAD, while 16% were unlabeled/Glu, 9% were unlabeled/GAD, and 16% expressed other transmitter combinations. Regional analysis of these interactions showed that 43% occurred in the MS, 22% in VHT1, 14% in SON, 9% in PVN, and 12% in the ME. AXO/DEN interactions made up 51% of all labeled interactions characterized, and were comprised 29% of Glu/GAD, 22% of Glu/Glu, and 18% of the Glu/Glu, and 18% of the Glu/Glu + GAD type. AXO/DEN synapses were more prevalent than contacts in all areas except the PVN and of course the ME, where anatomical synapses do not occur. AXO/SOM interactions represented approximately 15% of all those identified, and were predominantly unlabeled/Glu (71%) and unlabeled/GAD (18%) synapses. Almost all (95%) AXO/SOM synapses and 75% of the contacts occurred in the MS. DEN/DEN interactions, 28% of the total, were composed 50% of Glu/GAD, 12% of Glu/Glu, and 18% of the Glu/Glu+GAD type. The relatively few DEN/DEN synapses all appeared in the MS, whereas much more abundant DEN/DEN contacts were more widely distributed. DEN/SOM interactions, 6% of the total, appeared only as contacts, with the majority (60%) again located in the MS. In addition, the MS contained 48% of all asymmetrical synapses (vs. 35% in VHT1 and 17% in SON), 62% of all symmetrical synapses (vs. 19% in VHT1 and 14% in SON), and 35% of all contacts (vs. 21% in VHT1 and 12% in SON) identified.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Regional distribution of rat growth hormone releasing factor-like immunoreactivity in rat hypothalamus.

A heterologous RIA for rat GH-releasing factor (rGRF) was established using synthetic rGRF-(1-43)OH for both standard reference and radioiodination with the antiserum produced against human GRF-(1-44) NH2. The regional distribution of rGRF-like immunoreactivity (LI) in rat hypothalamus was examined according to the Palkovits microdissection method and compared with that of somatostatin (SRIF)-LI. Both rGRF- and SRIF-LI contents (mean +/- SE; nanograms per mg protein) were highest in the median eminence (rGRF, 32.28 +/- 11.42; SRIF, 109.9 +/- 19.2) and next most abundant in the arcuate nucleus (rGRF, 3.50 +/- 0.47; SRIF, 12.88 +/- 0.60). Only a small amount of rGRF-LI was found in the ventromedial (1.41 +/- 0.51) and dorsomedial (1.16 +/- 0.15) nuclei and the anterior hypothalamic area (1.29 +/- 0.42), whereas rGRF-LI was not detected in the other nuclei of the hypothalamus. A considerable amount of SRIF-LI was contained in the periventricular, ventromedial, and paraventricular nuclei and the anterior hypothalamic area, in accordance with other reports. Gel filtration chromatography revealed that hypothalamic extracts contained a major peak of rGRF-LI corresponding to rGRF-(1-43)OH and two peaks of SRIF-LI equivalent to SRIF-(1-28) and SRIF-(1-14), respectively. These findings indicate that rGRF-LI is localized in the median eminence and arcuate nucleus in the rat and that rGRF-, SRIF-(1-28)-, and SRIF-(1-14)-LI are present in a 1:2.10:6.29 ratio on a molar basis.

Animals↗
PubMed1987

Neuropeptide Y levels in microdissected regions of the hypothalamus and in vitro release in response to KCl and prostaglandin E2: effects of castration.

Intracerebroventricular administration of neuropeptide Y (NPY) has been shown to modify LH secretion, with the direction of the response dependent on the steroid background. To study further the role of gonadal steroids in the regulation of NPY secretion, the basal and KCl-evoked release of NPY from the medial basal hypothalamus (MBH) of intact and castrated male rats was assessed twice with the use of an in vitro incubation system. In each experiment, the amounts of NPY released in response to a 15-min pulse of KCl (45 mM) were significantly smaller from the MBH of castrated rats than of intact rats (P less than 0.05). Next, to assess the possible effects of prostaglandin E2 (PGE2), the MBH were exposed in a similar manner to two 15-min pulses, 30 min apart, of 0.568 and 56.8 mumol PGE2. Unlike KCl, PGE2 failed to stimulate NPY release from the MBH of either intact or castrated rats. However, a similar 56.8 mumol concentration of PGE2 was effective in stimulating the release of LHRH. We next examined the effects of castration on NPY levels in several microdissected regions of the hypothalamus. Whereas NPY concentrations were unchanged in the medial preoptic area, paraventricular nucleus and dorsomedial nucleus, NPY levels were significantly decreased in the median eminence, arcuate nucleus, and ventromedial nucleus 2 weeks after castration. These studies show that KCl can stimulate NPY release from the MBH in vitro, like that of LHRH, the KCl-induced NPY response is significantly smaller from the MBH of castrated than intact males, castration can significantly reduce the levels of NPY in the median eminence, arcuate nucleus, and ventromedial nucleus, thereby suggesting that testicular secretions may modulate NPY levels and release from the MBH, and because PGE2 stimulated the release of LHRH but not of NPY, separate regulatory neural events may underlie the secretion of these two neuropeptides.

Animals↗
PubMed1989

Testosterone raises neuropeptide-Y concentration in selected hypothalamic sites and in vitro release from the medial basal hypothalamus of castrated male rats.

Although neuropeptide-Y (NPY)-containing neurons are widely distributed in the hypothalamus, castration decreased NPY concentrations only in the median eminence (ME), arcuate nucleus (ARC), and ventromedial nucleus (VMN). We have now examined the effects of testosterone (T) replacement in 2-week castrated male rats on NPY levels in hypothalamic and preoptic area regions and in vitro NPY release in three experiments. In the first experiment we studied the effect of T on NPY concentration in castrated rats. Two-week castrated rats were implanted sc with T-filled or empty Silastic capsules 30 mm in length. Ten days later rats were killed, and NPY levels were measured by RIA in microdissected sites. T implants raised serum T levels to the range found in gonad-intact rats and decreased serum LH levels to the basal range. Further, of the six brain sites examined, significant increases in NPY concentrations occurred selectively in the ME, ARC, and VMN of T-implanted rats. In the second experiment, the ability of T to reverse the effect of castration on NPY levels compared to those in intact (sham) rats was assessed. Again, castration decreased NPY levels in the ME, ARC, and VMN only, and replacement of physiological levels of T restored NPY levels approximately 100%, 127%, and 74% in the ARC, VMN, and ME, respectively. In the third experiment, the effect of castration and T implants (30-mm T capsules for 10 days) to 2-week castrated rats on the in vitro release of NPY from medial basal hypothalamus (MBH) was assessed. Basal NPY release was not significantly changed after castration and T replacement. However, in response to a 30-min pulse of KCl (45 mM) NPY release from the MBH of castrated rats was significantly reduced compared to that in intact and T-replaced castrated rats. These studies show that castration decreases and T replacement restores NPY levels selectively in three hypothalamic sites, viz. ME, ARC, and VMN, and KCl-induced NPY release from the MBH in vitro is decreased after castration and restored by T replacement, thereby suggesting that a local subset of androgen-concentrating neurons may regulate NPY levels and release in a site-specific manner. Further, these results are in line with our emerging view that gonadal steroids modulate neurosecretion not only of LHRH, but also of other functionally linked regulatory peptides.

Animals↗
PubMedDate not supplied

[Excitability of the hypothalamus and limbic structures of the rabbit brain under the influence of glucocorticoids and ACTH].

The influence of glucocorticoids and ACTH on the excitability of the hypothalamus and limbic structures of the brain in rabbits was studied in chronic tests with electrochemotrodes preliminarily implanted into the brain. Results bearing proof to a dissimilar effect produced by ACTH and glucocorticoids on the excitability of the anterior and posterior hypothalamus, hippocampus and amygdala are presented. It is suggested that the mechanism of the retroinhibitory action of corticosteroids and ACTH provides for the participation of hypothalamic and limbic structures of the brain.

Adrenocorticotropic Hormone↗
PubMed1977

[Morphological studies of the matrix in human hypothalamus].

The variations of matrix and ependyma in the hypothalamus was histologicaly investigated in 120 human brains of both sexes from the 13 week old fetuses up to the end of the first year of postnatal life. The plane of cuts were in the region of the anterior hypothalamic nucleus, of the ventromedial nucleus, and the arcuate nucleus. We have found that the exhaustion of the matrix begins in the 14 week old embryo in the anterior and medial hypothalamus. A subependymale zone is present in these areas in the 17 week old embryo and exists up to 23 week. The one-cell-layer ependyma appears in the anterior are of the ventromedial nucleus at first in the 24 week week old embryo. After this the ependyma appears from the 25 to the 28 week old embryo in the regions of the anterior hypothalamic nucleus and the other areas of the ventromedial nucleus. In the immediate surrounding of the arcuate nucleus we observed the first alterations in the 15 week old embryo. The exhaustion of matrix is a continuous process up to the 23rd week. The boundary of the third ventricle remained to be a multilayer and in all stages of development cells were found, which reach into the lumen. Only after birth the multilayer boundary was reduced. At the end of the first year of postnatal life the one-layer ependyma was developed at a few sites. We could not find any significant variations of matrix exhaustion in the different sexes.

Ependyma↗
PubMed1981

Cardiovascular response to electrical stimulation of and microinjection of ouabain into posterior and ventromedial hypothalamus of cat.

Electrical stimulation (ES) of and injection of ouabain into ventromedial hypothalamus (VMH) of cats elicited only minor changes in heart rate (HR) and blood pressure (BP). On the other hand similar treatments to posterior hypothalamus (PH) consistently produced a significant increase in HR and BP; two out of five animals developed cardiac arrhythmias. The study suggests that PH is a potential site of action of ouabain for induction of arrhythmias.

Animals↗
PubMed1980

[Changes in the neuronal activity of the lateral geniculate bodies upon stimulation of the motivational centers of the hypothalamus].

In experiments on immobilized unanesthetized cats it was found that electrical stimulation of anterior hypothalamic areas and lateral hypothalamus causes predominantly a suppression of background activity of lateral geniculate neurons. Changes of light evoked activity were mostly of modulating character. During stimulation of the ventromedial nucleus of the hypothalamus a predominance of activating changes in background activity of lateral geniculate neurons was observed.

Animals↗
PubMed1997

Organization of efferent projections from the parabrachial area to the hypothalamus: a Phaseolus vulgaris-leucoagglutinin study in the rat.

The organization of projections from the parabrachial (PB) area to the hypothalamus was studied in the rat by using microinjections of Phaseolus vulgaris-leucoagglutinin (PHA-L) into subregions of the PB area. The present study is a follow-up of two former studies (Bernard et al. [1993] J. Comp. Neurol. 329:201-229; Aldén et al. [1994] J. Comp. Neurol. 341:289-314) that examined PB projections onto the amygdala and the bed nucleus of the stria terminalis. The results demonstrate that 1) the mesencephalic PB region, centered in the lateral portion of the superior lateral subnucleus projects extremely densely to almost the entire dorsomedial subdivision of the ipsilateral ventromedial hypothalamic nucleus; 2) the mesencephalic PB region, located in the medial portion of the superior lateral subnucleus and weakly overflowing into the rostralmost dorsal lateral pontine subnucleus, projects densely to the retrochiasmatic area and, to a lesser extent, to the ipsilateral ventromedial nucleus of the hypothalamus; 3) the PB region, including the central lateral, a portion of the superior lateral, and the outer external lateral subnuclei, projects densely to the ipsilateral median, anteroventral, and periventricular preoptic hypothalamic nuclei and projects more weakly to the dorsal border of the paraventricular nucleus (PVN). No consistent projection was found in the magnocellular PVN. All of these PB regions also project diffusely to the dorsomedial area and to a small tuberal subfornical hypothalamic area. In addition, the medial half of the PB area projects consistently to the posterior lateral hypothalamus. It is suggested that these pathways may be involved in aversive-defensive behavior, in autonomic and neuroendocrine aspects of pain, and in feeding and energy metabolism regulation.

Amygdala↗
PubMed2000

CART peptide immunoreactivity in the hypothalamus and pituitary in monkeys: analysis of ultrastructural features and synaptic connections in the paraventricular nucleus.

Cocaine and amphetamine regulated transcript (CART) has been identified as one of the most abundant mRNAs in the rat hypothalamus. The objective of the present study was to elucidate the distribution of CART peptide immunoreactive (CARTir) neurons in the monkey hypothalamus and characterize their ultrastructural features and synaptic connections in the paraventricular nucleus (PVN). CARTir neurons were particularly abundant in the PVN, supraoptic nucleus (SON), infundibular nucleus, and premammillary nucleus, whereas the anterior, lateral, and posterior hypothalamic areas as well as the posterior nucleus displayed moderate immunoreactivity. Dense bundles of CARTir fibers exited the PVN and SON and followed a trajectory to the infundibulum similar to that previously shown for vasopressin and oxytocin fibers. The posterior pituitary was densely packed with large CARTir varicosities which, in some cases, were apposed to labeled pituicytes. The external/palisade zone of the median eminence contained rich plexuses of small CARTir varicose fibers, and the internal/fibrous zone was enriched in large axon-like processes. Electron microscope analysis of the PVN revealed (1) that CART peptide immunoreactivity is found in neurosecretory and non-neurosecretory neurons contacted predominantly by unlabelled terminals forming asymmetric synapses, (2) that CARTir terminals resemble glutamatergic and/or noradrenergic boutons and form asymmetric synapses with non-neurosecretory dendrites, and (3) that neuropeptide Y (NPY)-containing terminals are apposed to CARTir neurons in the medial part of the nucleus. In conclusion, our findings demonstrate that CART peptide is abundant in neuronal perikarya and axon terminals throughout the monkey hypothalamus and along the hypothalamopituitary axis. This strengthens the idea that CART peptides may act as putative neurotansmitters/neuromodulators that mediate various neuroendocrine and autonomic functions in primates.

Animals↗
PubMed1996

Distribution of aromatase-immunoreactive cells in the forebrain of zebra finches (Taeniopygia guttata): implications for the neural action of steroids and nuclear definition in the avian hypothalamus.

Cells immunoreactive for the enzyme aromatase were localized in the forebrain of male zebra finches with the use of an immunocytochemistry procedure. Two polyclonal antibodies, one directed against human placental aromatase and the other directed against quail recombinant aromatase, revealed a heterogeneous distribution of the enzyme in the telencephalon, diencephalon, and mesencephalon. Staining was enhanced in some birds by the administration of the nonsteroidal aromatase inhibitor, R76713 racemic Vorozole) prior to the perfusion of the birds as previously described in Japanese quail. Large numbers of cells immunoreactive for aromatase were found in nuclei in the preoptic region and in the tuberal hypothalamus. A nucleus was identified in the preoptic region based on the high density of aromatase immunoreactive cells within its boundaries that appears to be homologous to the preoptic medial nucleus (POM) described previously in Japanese quail. In several birds alternate sections were stained for immunoreactive vasotocin, a marker of the paraventricular nucleus (PVN). This information facilitated the clear separation of the POM in zebra finches from nuclei that are adjacent to the POM in the preoptic area-hypothalamus, such as the PVN and the ventromedial nucleus of the hypothalamus. Positively staining cells were also detected widely throughout the telencephalon. Cells were discerned in the medial parts of the ventral hyperstriatum and neostriatum near the lateral ventricle and in dorsal and medial parts of the hippocampus. They were most abundant in the caudal neostriatum where they clustered in the dorsomedial neostriatum, and as a band of cells coursing along the dorsal edge of the lamina archistriatalis dorsalis. They were also present in high numbers in the ventrolateral aspect of the neostriatum and in the nucleus taeniae. None of the telencephalic vocal control nuclei had appreciable numbers of cells immunoreactive for aromatase within their boundaries, with the possible exception of a group of cells that may correspond to the medial part of the magnocellular nucleus of the neostriatum. The distribution of immunoreactive aromatase cells in the zebra finch brain is in excellent agreement with the distribution of cells expressing the mRNA for aromatase recently described in the finch telencephalon. This widespread telencephalic distribution of cells immunoreactive for aromatase has not been described in non-songbird species such as the Japanese quail, the ring dove, and the domestic fowl.

Animals↗