Partial co-existence of NADPH-diaphorase and acetylcholinesterase in the hypothalamic magnocellular secretory nuclei of the rat.

Co-localization of NADPH-diaphorase (ND) and acetylcholinesterase (AChE) activities were explored in the magnocellular secretory nuclei of the rat hypothalamus by means of a double histochemical staining of the same sections. Partial co-existence was found in all the nuclei studied (paraventricular, supraoptic, fornicals and circular nuclei). No particular location of the neurons expressing both markers was found, although in the paraventricular nucleus all of them (ND +, AChE + and neurons expressing both markers) were preferentially located in the magnocellular subdivisions whereas in the parvicellular ones only some neurons belonging to all three types were detected, mainly located in the periventricular and medial subdivisions. The lowest degree of co-existence was found at the level of the main magnocellular nuclei (supraoptic and paraventricular) when compared with the accessory magnocellular nuclei, especially the posterior fornical and the circular nuclei. These results extend previous data on the chemical nature of the neurons producing nitric oxide in the neurosecretory nuclei and the possible functional role of this atypical messenger in the hypothalamus.

Absence of coexistence between NADPH-diaphorase and antidiuretic hormone in the hypothalamus of two galliforms: Japanese quail (Coturnix japonica) and chicken (Gallus domesticus).

Based on previous studies demonstrating coexistence of NADPH-diaphorase (ND) and vasopressin (VP) in the rat hypothalamus. ND histochemistry and vasotocin (VT) immunocytochemistry have been combined in order to study the distribution of both markers in the hypothalamus of the Japanese quail (Coturnix japonica) and chicken (Gallus domesticus). No coexistence was found, however, close anatomical relationships between ND-positive and VT-immunoreactive elements were observed in specific preoptic and hypothalamic locations. These findings indicate interspecies differences in the expression of ND and the antidiuretic hormone with functional implications in osmoregulation.

Coexistence of NADPH-diaphorase with vasopressin and oxytocin in the hypothalamic magnocellular neurosecretory nuclei of the rat.

Coexistence of NADPH-diaphorase with vasopressin and oxytocin was studied in the magnocellular neurosecretory nuclei of the rat hypothalamus by use of sequential histochemical and immunocytochemical techniques in the same sections. Coexistence was found in all the nuclei examined (supraoptic, paraventricular, circular, fornical, and in some isolated neurons located in the hypothalamic area between the paraventricular and supraoptic nuclei). The ratios of neurons expressing both markers (NADPH-diaphorase and vasopressin, NADPH-diaphorase and oxytocin) in each of the nuclei were very similar. Although further studies must be carried out, the partial coexistence found in all nuclei suggests that NADPH-diaphorase is probably not related to general mechanisms involving vasopressin and oxytocin, but rather in specific functions shared by certain hypothalamic neuronal cell populations.

Calretinin immunoreactivity in the magnocellular neurosecretory nuclei of the rat hypothalamus.

The distribution of calretinin-immunoreactivity in the magnocellular neurosecretory nuclei of the rat hypothalamus was studied using a polyclonal antibody and the avidin-biotin immunoperoxidase technique. Calretinin-immunoreactive neurons were observed in the supraoptic and paraventricular nuclei. Additionally, we detected for the first time, immunoreactive neurons located in the circularis and fornicals nuclei, and isolated positive neurons situated in the hypothalamic area located between the supraoptic and paracentricular nuclei. When these results were compared to those obtained in previous studies for another two calcium-binding proteins: calbindin D-28k and parvalbumin, two major differences may be concluded: a) a different distribution of calretinin, especially in the paraventricular nucleus, and b) an expression of calretinin lower than calbindin D-28k and higher than parvalbumin in the magnocellular hypothalamic nuclei. Of special interest is the fact that calretinin is one of the few markers which demonstrates predominantly parvicellular neurons in the paraventricular nucleus. Although the exact biochemical function of these three calcium-binding proteins remains unknown, their uneven and characteristic distributions strongly suggest that specific neuronal populations in the hypothalamus may use alternatively different calcium-sequestering molecules.

Infrequent cellular coexistence of NADPH-diaphorase and calretinin in the neurosecretory nuclei and adjacent areas of the rat hypothalamus.

Colocalization of the calcium-binding protein calretinin and NADPH-diaphorase activity at the cellular level was studied in the magnocellular secretory nuclei of the rat hypothalamus using sequential immunocytochemical and histochemical staining of the same sections. A low degree of colocalization of these markers was observed in certain cellular subpopulations within all the areas considered (supra-optic, paraventricular, circular and both fornicals nuclei and in the hypothalamic area located between the supraoptic and paraventricular nuclei). However, since in the paraventricular nucleus both markers were expressed by different neuronal populations, the coexistence was almost non-existent in some subdivisions of this nucleus. This rare coexistence strongly suggests that NADPH-diaphorase and calretinin are related to different functions shared by restricted hypothalamic neuronal populations.

NADPH-diaphorase activity in the hypothalamic magnocellular neurosecretory nuclei of the rat.

A histochemical study of the distribution of NADPH diaphorase activity in the hypothalamus of normal rats was carried out. Our study demonstrates the presence of NADPH-diaphorase activity in the circularis and anterior and posterior fornicals nuclei for the first time. Additionally, we confirm the presence of NADPH-diaphorase-stained neurons in the paraventricular (both magno- and parvicellular neurons) and supraoptic nuclei, as well as a population of isolated positive neurons (not included in any hypothalamic nuclei) located among the different nuclei. Because NADPH diaphorase has recently been shown to be a nitric oxide synthase, our study reveals a wide presence of this enzymatic activity in the hypothalamus of the rat.

CaBP D-28k and NADPH-diaphorase coexistence in the magnocellular neurosecretory nuclei.

Coexistence of the calcium binding protein calbindin D-28k and NADPH-diaphorase activity was studied in the magnocellular secretory nuclei of the rat hypothalamus using both immunocytochemical and histochemical techniques. Coexistence was found in all the nuclei considered (supraoptic, paraventricular, circularis and fornicals nuclei) with the exception of the hypothalamic area situated between the supraoptic and the paraventricular nuclei. Since both stainings are reliable markers, not based upon the physiological characteristics at a given moment, our study provides a further characterization of the neurons in the magnocellular neurosecretory nuclei.

Calbindin D-28K- and parvalbumin-reacting neurons in the hypothalamic magnocellular neurosecretory nuclei of the rat.

The distribution of calbindin D-28K- and parvalbumin-reacting neurons in the hypothalamic magnocellular neurosecretory nuclei of the rat was studied using the avidin-biotin-immunoperoxidase method and highly specific monoclonal antibodies. Incubation with anticalbindin D-28K-antiserum revealed immunoreactive neurons in the following nuclei: supraoptic, paraventricular (both in the magnocellular and parvicellular regions), circularis, fornicals and medial forebrain bundle. Incubation with parvalbumin antiserum displayed immunoreactive neurons only in the circularis nucleus. Additionally, it was possible to observe scattered calbindin and parvalbumin immunoreactive neurons (which do not form part of the nuclei considered) located in the hypothalamic area between the supraoptic and the paraventricular nuclei, especially for the calbindin D-28K antiserum.

Distribution of parvalbumin-immunoreactivity in the rat thalamus using a monoclonal antibody.

1. The distribution of parvalbumin cell bodies and fibers in the thalamus of the rat was studied using a monoclonal antibody and the avidin-biotin-peroxidase method. The densest clusters of immunoreactive perikarya were observed in the nuclei ventralis posterior, reticularis, ventralis anterior and zona incerta, whereas the nuclei habenularis lateralis, lateralis posterior, lateralis, centralis lateralis and ventralis lateralis had the lowest density. In the nucleus geniculatum laterale ventralis, the density of parvalbumin cell bodies was intermediate. In all these thalamic nuclei, small, round or fusiform immunoreactive cells with short immunolabeled dendritic processes were observed. 2. The densest network of immunoreactive fibers was observed in the nuclei geniculatum laterale ventralis, reticularis and zona incerta. The nuclei geniculatum laterale dorsalis, ventralis posterior, medialis ventralis, ventralis anterior, anterior ventralis, anterior dorsalis and rhomboidens contained a moderate number of parvalbumin fibers, whereas the nuclei lateralis posterior, habenularis lateralis, parataenialis, centrum medianum, lateralis, centralis lateralis, ventralis lateralis, medialis dorsalis, anterior medialis, ventralis medialis and lateralis anterior had the lowest density of immunoreactive fibers. In addition, a large number of immunoreactive fibers was found in the lemniscus medialis and a scarce number in the stria medullaris. 3. No immunoreactive structure was observed in the nuclei habenularis medialis, paraventricularis, reuniens and geniculatum mediale. 4. Thus, perikarya and fibers containing parvalbumin are widely distributed throughout the thalamus of the rat, suggesting that parvalbumin might play a role, directly or indirectly, in limbic, visual and somatosensory mechanisms.

Different roles of intrahypothalamic and nigrostriatal dopaminergic systems in thermoregulatory responses of the rat.

Classically, two neurotransmitters in the brain have been implicated in thermoregulation: 5-hydroxytryptamine and norepinephrine. A dopamine action is less well-known and usually has been studied by means of pharmacological rather than physiological procedures. In the present work using a physiological approach to the problem, the role of different central dopaminergic systems in the thermoregulatory response of rats exposed to cold (4 degrees C) or warm (45 degrees C) environments has been studied. Rostral incertohypothalamic neurons in the medial preoptic area synthesized and released more dopamine in response to a warm but not to a cold environment. On the other hand DA and DOPAC levels in nigrostriatal systems were decreased by cold but not warm environments. The dopaminergic neurons projecting to nucleus accumbens or hypothalamus do not appear to be related to the thermoregulatory response in the rat.