Relationship of alpha MSH-specific neurons to the arcuate opiocortin neuronal system as determined by dual antigen immunocytochemical procedures

Neuronal activation by stimuli that predict sexual reward in female rats

Conditioned stimuli (CSs) associated with paced copulation induce a conditioned partner preference for males bearing the CS. Here we examined the activation of Fos immunoreactivity (Fos-IR) following exposure to a CS previously paired with either paced or nonpaced copulation. Ovariectomized, hormone-primed rats received 10 sequential conditioning trials at 4-day intervals. In experiment 1, females in the odor-paired group learned to associate an almond odor on a male with paced copulation and an unscented male with nonpaced copulation. In the odor-unpaired group, females received the opposite association. In experiment 2, females associated two different strains of male, Long-Evans or Wistar, with paced or nonpaced copulation, respectively. A preference test indicated that females in both experiments developed a conditioned preference for the pacing-related males, as indicated by significantly more solicitations toward the male and a preference to copulate with the pacing-related male. Subsequently, females were exposed to the CS (odor or strain) alone for 1 h prior to kill and preparation of their brains for immunocytochemistry. In both experiments, the CS associated with paced copulation produced significantly more Fos-IR in the piriform cortex, medial preoptic area, and ventral tegmental area, relative to the same odor or strain cues associated with nonpaced copulation. These findings provide evidence that the state associated with paced copulation can be conditioned to environmental stimuli such as neutral odors or strain cues, which earn an incentive value via classical conditioning. The significance of the brain areas activated is discussed with regard to their role in sexual and other motivated behaviors.

Pathway tracing using biotinylated dextran amines

Biotinylated dextran amines (BDA) are highly sensitive tools for anterograde and retrograde pathway tracing studies of the nervous system. BDA can be reliably delivered into the nervous system by iontophoretic or pressure injection and visualized with an avidin-biotinylated HRP (ABC) procedure, followed by a standard or metal-enhanced diaminobenzidine (DAB) reaction. High molecular weight BDA (10 k) yields sensitive and exquisitely detailed labeling of axons and terminals, while low molecular weight BDA (3 k) yields sensitive and detailed retrograde labeling of neuronal cell bodies. The detail of neuronal cell body labeling can be Golgi-like. BDA tolerates EM fixation and processing well and can, therefore, be readily used in ultrastructural studies. Additionally, BDA can be combined with other anterograde or retrograde tracers (e.g. PHA-L or cholera toxin B fragment) and visualized either by multi-color DAB multiple-labeling - if permanent labels are desired, or by using multiple simultaneous immunofluorescence - if fluorescence viewing is desired. In the same manner, BDA pathway tracing and neurotransmitter immunolabeling can be combined. Note that BDA pathway tracing can also be combined with anterograde or retrograde labeling with fluorescent dextran amines, if one wishes to exclusively use tracers with the favorable transport properties and sensitivities of dextran amines. In this case, the BDA can be visualized together with the fluorescent dextran amines using fluorescence labeling for the BDA, or the fluorescent dextran amines can be visualized together with the BDA by multicolor DAB labeling via immunolabeling of the fluorescent dextran amines using anti-fluorophore antisera. BDA is, thus, a flexible and valuable pathway tracing tool that has gained widespread popularity in recent years.

Melanotropic peptides in the mammalian brain: the melanin-concentrating hormone

Melanin-concentrating hormone (MCH) has been identified in neurons of the mammalian brain. This review summarizes some current information regarding the cell biology of this neuropeptide and the topography of MCH-immunoreactive (-IR) neurons in several species including mouse, rat, hamster, guinea pig, rabbit, dog and monkey; and atlas of MCH-IR neurons in the hypothalamus and subthalamus of the brain of guinea pig is presented. Based upon the location of this MCH cell group, it is hypothesized that they may be functionally involved in circuits of extrapyramidal motor systems from striatal centers to the thalamus and cerebral cortex and to the midbrain and spinal cord.

Immunohistochemical mapping of neuropeptides in the premamillary region of the hypothalamus in rats

The topographical distribution of neuropeptide-containing cell bodies, fibers and terminals was studied in the premamillary region of the rat hypothalamus using light microscopic immunohistochemistry. Alternate coronal sections through the posterior third of the hypothalamus of normal and colchicine-treated male rats were immunostained for 19 different neuropeptides and their distributions were mapped throughout the following structures: the ventral and dorsal premamillary, the supramamillary, the tuberomamillary and the posterior hypothalamic nuclei, as well as the premamillary portion of the arcuate nucleus and the postinfundibular median eminence. Seventeen of the investigated neuropeptides were present in neuronal perikarya, nerve fibers and terminals while the gonadotropin associated peptide and vasopressin occurred only in fibers and terminals. Growth hormone-releasing hormone-, somatostatin-, alpha-melanocyte stimulating hormone-, adrenocorticotropin-, beta-endorphin- and neuropeptide Y-immunoreactive neurons were seen exclusively in the premamillary portion of the arcuate nucleus. Thyrotropin-releasing hormone-, dynorphin A- and galanin-containing neurons were distributed mainly in the arcuate and the tuberomamillary nuclei. A high number of methionine- and leucine-enkephalin-immunoreactive cells were detected in the arcuate and dorsal premamillary nuclei, as well as in the area ventrolateral to the fornix. Substance P-immunoreactive perikarya were present in very high number within the entire region, in particular in the ventral and dorsal premamillary nuclei. Cell bodies labelled with cholecystokinin- and calcitonin gene-related peptide antisera were found predominantly in the supramamillary and the terete nuclei, respectively. Corticotropin-releasing hormone-, vasoactive intestinal polypeptide- and neurotensin-immunoreactive neurons were scattered randomly in low number, mostly in the arcuate and the ventral and dorsal premamillary nuclei. Peptidergic fibers were distributed unevenly throughout the whole region, with each peptide showing an individual distribution pattern. The highest density of immunoreactive fibers was presented in the ventral half of the region including the arcuate, the ventral premamillary and the tuberomamillary nuclei. The supramamillary nucleus showed moderately dense fiber networks, while the dorsal premamillary and the posterior hypothalamic nuclei were poor in peptidergic fibers.

Interaction between adrenergic fibers and intermediate cholinergic neurons in the rat spinal cord: a new double-immunostaining method for correlated light and electron microscopic observations

Relationships between cholinergic neurons and adrenergic fibers in the intermediate region of the rat thoracic spinal cord were examined using a new immunohistochemical double-staining method for light and electron microscopic observations. Cholinergic neurons were labeled by a monoclonal antibody to choline acetyltransferase and stained bluish green by 5-bromo-4-chloro-3-indolyl-beta-D-galactoside reaction products using beta-galactosidase as a marker. On the same sections, adrenergic fibers were labeled by a polyclonal antiserum to phenyl-ethanolamine-N-methyltransferase and stained brown by diaminobenzidine reaction products using peroxidase as a marker. After embedding in Epon, the sections were examined in the light and electron microscopes. In the light microscope, choline acetyltransferase-like immunoreactive cells were seen in the four discrete areas of the intermediate region: the principal intermediolateral nucleus, the central autonomic nucleus, the intercalated nucleus and the funicular intermediolateral nucleus. These cell groups seemed to be connected to each other by their processes, and they showed a "ladder-like appearance" as a whole. Phenylethanolamine-N-methyltransferase-like immunoreactive fibers were present only along this "ladder-like structure" and were the most rich in the principal intermediolateral nucleus. In the electron microscope, some of the choline acetyltransferase-like immunoreactive neurons, which were identified by light micrographs, were found to receive synaptic inputs from phenylethanolamine-N-methyltransferase-like immunoreactive boutons in the principal intermediolateral nucleus. These findings suggest that the adrenergic axons in the principal intermediolateral nucleus directly affect the activity of the cholinergic preganglionic sympathetic neurons.

Immunocytochemical evidence for alpha-melanocyte-stimulating hormone in the hypothalamus of the frog Rana esculenta

The distribution of immunoreactive alpha-melanocyte-stimulating hormone (alpha-MSH) within the brain of the frog, Rana esculenta, has been studied on adjacent serial sections using an indirect immunofluorescence technique. Immunoreactive cell bodies are found in the anterior part of the preoptic nucleus and in some ventral subependymal cerebrospinal fluid-contacting elements, and in the nucleus infundibularis ventralis. Numerous alpha-MSH-like immunoreactive fibers are present in the preoptic area, in the pars ventralis of the tuber cinereum, and in the outer layer of the median eminence. This staining pattern is completely eliminated after preabsorbing the antiserum with the corresponding antigen, but blocking tests with alpha-MSH-related peptides do not lead to any change in the immunoreaction. From these results it may be inferred that an alpha-MSH-like system is present in the hypothalamic neurosecretory area of R. esculenta, and is probably related to its hypophysiotropic functions. The results are compared to the distribution of alpha-MSH within the hypothalamus of reptiles and mammals.

Staining of magnocellular neurons of the supraoptic and paraventricular nuclei with vasopressin anti-idiotype antibody: a potential method for receptor immunocytochemistry

A vasopressin anti-idiotype antibody was generated by immunization with a primary anti-vasopressin IgG. This antibody was capable of immunostaining vasopressinergic neurons in the supraoptic and paraventricular nuclei of the hypothalami of normal and Brattleboro rats. Staining was eliminated by preabsorption or coincubation of the antibody with a vasopressin binding protein prepared from rat neural membranes. The anti-idiotype also inhibited binding of [3H]vasopressin to this neural membrane protein in a dose-dependent manner. These experiments suggest that the anti-idiotype antibody recognizes a receptor associated with vasopressinergic neurons.

Co-existence of CRF and vasopressin immunoreactivity in parvocellular paraventricular neurons of rat hypothalamus

New dual immunocytochemical staining procedures were used in the same tissue section to elucidate the distribution and co-existence of CRF and vasopressin in parvocellular neuronal perikarya in the paraventricular nucleus (PVN) of rat hypothalamus. CRF immunostained cells were for the most part concentrated in the medial parvocellular component of PVN. Few vasopressin-immunoreactive (ir) neurons were seen in this area in the normal and colchicine-treated animals. Vasopressin-containing neurons predominated in the magnocellular component of PVN. In the adrenalectomized and adrenalectomized-colchicine-treated animals, a dense accumulation of vasopressin-ir cells were observed in the medial parvocellular area of PVN; this region is normally vasopressin-ir poor and CRF-ir rich. The vasopressin immunostained cells appeared to have an anatomical distribution similar to that seen for CRF-containing cell bodies. Results of this study unequivocally establish the co-existence of vasopressin and CRF in the same parvocellular perikarya of PVN following pertubation of the pituitary-adrenal axis.

Dual immunostaining procedure demonstrating neurotransmitter and neuropeptide codistribution in the same brain section

A method for sequential immunostaining of two antigens in the same section and the application to neuronal elements in the CNS is described. This method employs the peroxidase-antiperoxidase (PAP) technique as a first sequence, followed by glucose oxidase-antiglucose oxidase (GAG) complex as the second sequence, yielding rich brown and vibrant blue reaction products, respectively. Application of the PAP/GAG immunoreagents as dual markers for various neuropeptide and neurotransmitter systems is described in detail and the procedure is outlined. Comparisons with other dual staining methods are discussed and the application to other systems is presented.

Ultrastructural characteristics of peptidergic neurons using pre-embedding immunocytochemical methods

The immunocytochemical staining technique represents a valuable method for electron microscopic analysis with which to elucidate the ultrastructural characteristics, synaptology, and potential interactions of selectively labeled neuronal systems. The unlabeled antibody peroxidase-antiperoxidase (PAP) technique is one of the most widely used immunocytochemical methods and has been applied to both pre-embedding and postembedding EM procedures. This review provides a detailed protocol for the former method and discusses advantages and disadvantages associated with the use of both approaches. A descriptive fine structural analysis of peptidergic neurons localized in the hypothalamus of brain illustrates the applicability and specificity of utilizing this method for the localization of cellular antigens of other systems.

Relationship of ACTH1-39-immunostained fibers and magnocellular neurons in the paraventricular nucleus of rat hypothalamus

Dual antigen immunocytochemical staining procedures were used in the same tissue section to determine the distribution of ACTH immunostained fibers and varicosities within the magnocellular and parvocellular divisions in the paraventricular nucleus (PVN) of rat hypothalamus and elucidate its anatomical relationship to vasopressin (VP) and oxytocin (OXY)-containing neurons. Double immunostained preparations using glucose oxidase-antiglucose oxidase complex combined with PAP complex to visualize two antigens with contrasting colors in the same tissue section were employed. ACTH-immunoreactive (ir) fibers were distributed throughout the periventricular stratum and the parvocellular component of the PVN; in the latter area fibers were particularly dense in the ventral medial portion of the medial parvocellular division. Dual immunostained sections revealed a close anatomical association between opiocortin fibers and oxytocin and vasopressin parvocellular neurons. ACTH immunostained fibers were present in the anterior and medial magnocellular component of PVN and in the ventral medial portion of the posterior magnocellular division; these immunoreactive fibers were in intimate proximity to oxytocin-ir perikarya. The very close approximation between the ACTH-ir fibers and oxytocin-containing cell bodies suggests potential cell to cell communication between the two peptidergic systems in PVN. Few ACTH immunostained fibers were seen in the dorsal lateral portion of the posterior magnocellular division in which vasopressinergic neurons predominate. The present anatomical study supports pharmacological and physiological studies which indicate that opioids can influence the activity of magnocellular PV neurons. This study also elucidates an anatomical relationship between opiocortins (ACTH1-39) and parvocellular PV neurons which suggests that the opiocortin system may play a role in the regulation of both the neuroendocrine and autonomic activities of specific PV neurons.

Distribution of CRF- and tyrosine hydroxylase-immunoreactive neurons in the brainstem of the domestic fowl (Gallus domesticus)

The distribution of CRF and tyrosine hydroxylase (TH)-immunoreactive neurons was examined in the brainstem of the chicken. Very dense populations of both CRF and TH-immunoreactive (-ir) perikarya are co-extensive in separate neuronal systems throughout a large field of the rostral brainstem, encompassing locus ceruleus, the mesencephalic reticular formation, parabrachial nucleus, and the dorsal and ventral tegmental areas. They are present also in nucleus tractus solitarius, and sparsely in the ventral and lateral areas of the medulla. This co-distribution suggests that the effects of CRF upon central autonomic activity may be mediated via brainstem catecholamine systems. CRF-ir neurons alone are present also in midline nuclei, including n. centralis superior, n.annularis, n.linearis caudalis, and the raphe.