Sexually dimorphic level of CCK-8-like immunoreactive neuronal somata within several basal forebrain nuclei of the rat

Polyclonal IgY Antibodies from Chicken Egg Yolk — an Alternative to the Production of Mammalian IgG Type Antibodies in Rabbits

Based on a physiological process, antibodies are concentrated in the yolk of chicken eggs, and can be used as a convenient source of polyclonal antibodies. Hens were immunised with a BSA-cholecystokinin octapeptide conjugate (CCK-8) to obtain antibodies against CCK-8. A simple method is described for extracting the antibodies from egg yolk, which can then successfully be used in immunocytochemical studies. Using these antibodies, CCK-like immunoreactivity was found in brain sections of rats, both by fluorescein isothiocyanate and peroxidase staining. The specificities of these antibodies were different from those of rabbit antibodies against the C-terminal part of CCK-8.

The applicability of egg yolk antibodies in immunological investigations is reviewed and discussed in detail. The properties of avian egg yolk antibodies are compared with those of polyclonal antibodies obtained from mammals (e.g. the rabbit). The more general use of avian antibodies is emphasised as a real alternative, taking into consideration the reduction in animal suffering involved in comparison with the classical immunisation techniques used on rabbits.

Advantages of Using Egg Yolk Antibodies in the Life Sciences: The Results of Five Studies

It has been known for over a century that specific antibodies can be extracted from the eggs of immunised chickens. However, it was only when animal welfare became a subject of public debate that the chicken was considered as an alternative source of antibodies due to the possibility of non-invasive antibody sampling. Unfortunately, the welfare of animals alone is not sufficient to attract the interest of scientists; it is therefore important to demonstrate to potential users that avian antibodies can be used successfully in a variety of scientific investigations. The particular specificity of avian antibodies would appear to be due to the phylogenetic difference between Mammalia and Aves as well as to differences between the molecular structures of avian immunoglobulin (IgY) and mammalian immunoglobulin (IgG). The use of avian antibodies has additional advantages, as a considerable quantity of antibodies can be obtained from one chicken, and because the specificity of avian antibodies often markedly differs from that of comparable mammalian antibodies. This paper aims to demonstrate the advantages of using avian antibodies by presenting the results of five separate studies. In the first study, coordinated by Rüdiger Schade, the visualisation of cholecystokinin-like immuno-reactivity in the substantia nigra of rats by using anti-cholecystokinin antibody, without the pre-treatment of colchicine, is described. The second study, headed by Albrecht Zott, describes the use of avian antibodies in the identification of modern acellular pertussis vaccines by using rocket immunoelectrophoresis. The identification of unknown vaccine batches and the comparison with reference vaccines is a prerequisite for reducing the number of animal experiments necessary for vaccine control. The third study, coordinated by Martin Gerl, investigates the specificity of antibodies directed against the N-terminal propeptide of procollagen type III (PIIINP). Among the antibodies originating from different species (rabbit, mouse and chicken), only the chicken antibody was able to respond to the PIIINP in both human and rat sera. Thus, a direct comparison between human serum samples (alcoholic liver) and serum samples derived from corresponding animal models was possible. The fourth study, coordinated by Michael Erhard, shows that egg yolk antibodies can be successfully used to manage infectious diarrhoea in young agricultural animals. The final study, led by Andreas Hlinak, describes the successful production of anti-bovine leukaemia virus antibody. This antibody could be used in several diagnostic systems (for example, enzyme immunoassays and cytology). The five studies demonstrate that avian antibodies are an attractive alternative to mammalian antibodies, not only with respect to the welfare of animals, but also with respect to scientific and economic considerations.

Individual differences in novelty-seeking behavior in rats: a c-fos study

Novelty-seeking personality traits have been implicated in substance abuse and psychiatric disorders in humans. Novelty-seeking behaviors are also observed in rats, and individual rats exhibit substantial differences in expression of these behaviors. Thus, some rats exhibit low reactivity to novelty and high anxiety-like behavior and are termed low responders, while others are hyperresponsive to novelty and exhibit low anxiety-like behavior and are termed high responders. While we and others had shown differences in patterns of gene expression in high and low responding animals at rest, no studies have described their brain activation following an anxiety test. We report here that a 5-min exposure to an anxiogenic stressor induced distinct patterns of c-fos expression in the brains of high and low responding rats. When compared to low responders, high responding rats showed low expression of c-fos mRNA in the CA1 area of the hippocampus, but high c-fos mRNA levels in the olfactory area, the orbital cortex, the cingulate cortex, the dorsal striatum and the paraventricular nucleus of the hypothalamus. Given that c-fos is a trans-acting factor, we suggest that the short- and long-term consequences of the exposure to the anxiogenic stressor may also be quantitatively and anatomically different in these two groups of animals. Thus, these c-fos results demonstrate how experience may further exaggerate individual differences. Animals that differ in emotional reactivity not only exhibit basal differences in gene expression, but also react to novelty with different molecular responses, further increasing the neuronal differences between them.

Roles of steroid hormones and their receptors in structural organization in the nervous system

Due to their chemical properties, steroid hormones cross the blood-brain barrier where they have profound effects on neuronal development and reorganization both in invertebrates and vertebrates, including humans mediated through their receptors. Steroids play a crucial role in the organizational actions of cellular differentiation representing sexual dimorphism and apoptosis, and in the activational effects of phenotypic changes in association with structural plasticity. Their sites of action are primarily the genes themselves but some are coupled with membrane-bound receptor/ion channels. The effects of steroid hormones on gene transcription are not direct, and other cellular components interfere with their receptors through cross-talk and convergence of the signaling pathways in neurons. These genomic and non-genomic actions account for the divergent effects of steroid hormones on brain function as well as on their structure. This review looks again at and updates the tremendous advances made in recent decades on the study of the role of steroid (gonadal and adrenal) hormones and their receptors on developmental processes and plastic changes in the nervous system.

Cholecystokinin excites neostriatal neurons in rats via CCKA or CCKB receptors

The effect of iontophoretically applied cholecystokinin (CCK) on neurons of the neostriatum was studied in rats anaesthetized with urethane. The most frequently observed effect of the sulphated octapeptide (CCK-8S) on striatal neurons was excitation. Spontaneously active neurons responded more often to CCK-8S than quiescent cells. Silent, primarily non-responsive neurons could often be stimulated with CCK-8S using glutamate to induce an ongoing discharge. Thus, 45.8% of the 177 neurons studied changed their discharge rate by more than 30%. Certain CCK receptor antagonists could prevent the effect of CCK-8S, fully or at least partly, in the majority of CCK-responsive neurons. The data suggest that cholecystokinin modulates the firing of active neostriatal neurons via the CCKA or the CCKB receptor type. Furthermore, we compared neuronal responses to glutamate with those recorded during concomitant administration of CCK-8S in order to study the interaction of both transmitters, which may be colocalized in striatal afferents. CCK-8S mainly enhanced the excitatory effect of glutamate on striatal neurons, but in several neurons the response to glutamate was reduced. The CCKB receptor antagonist could prevent CCK-8S from increasing the glutamate-induced activation.

Ultrastructural study of CCK and tyrosine hydroxylase immunoreactivity in the rat nucleus accumbens

The cholecystokinin (CCK)- and tyrosine hydroxylase (TH)-like immunoreactive (LI) axons and boutons were studied in the caudal and medial parts of the rat nucleus accumbens (NAC), using the indirect immunoperoxidase technique, at the electron microscopic level. Both CCK- and TH-LI boutons contained clear synaptic vesicles and large granular vesicles of similar size, but the CCK-LI boutons contained more large granular vesicles than TH-LI boutons. The CCK-LI and TH-LI boutons were heterogeneous. This finding might be related to the various immunoreactive neuronal types innervating the caudomedial NAC. However, the CCK-LI boutons (containing mostly small, round, clear synaptic vesicles) formed mainly asymmetrical synaptic contacts with dendritic spines whereas the TH-LI boutons (containing medium-sized as well as small, round, clear synaptic vesicles) formed mostly symmetrical synaptic contacts with dendritic shafts.

Sex differences in densities of dopaminergic fibers and GABAergic neurons in the prenatal rat striatum

On the basis of observations on dopaminergic neurons developing in gender-specific cultures of embryonic rat mesencephalon, we have hypothesized that as yet unknown sexual dimorphisms might be found in projection areas of dopaminergic neurons. Therefore we searched for possible sex differences in the striatum during the period when massive ingrowth of mesencephalic afferents occurs and the striatal gamma-aminobutyric acid (GABA)ergic neurons differentiate. Male and female rats of embryonic days (E) 16, 18, 20, and 21 were fixed by perfusion through the heart. Vibratome sections were cut from the striatal anlage and sequentially immunostained for GABA by the immunogold-silver technique and tyrosine hydroxylase (TH) by the avidin-biotin-peroxidase method. Ultrathin sections were scanned for numbers of GABA- and TH-immunoreactive (IR) elements. Densities of TH-IR axons as well as of GABA-IR cell body profiles progressed with time. Contacts between TH-IR axons and GABA-IR and immunonegative cells were observed as early as E-16, increasing in numbers toward later stages. Throughout prenatal development, female striata displayed higher densities of both TH-IR axon and GABA-IR cell body profiles than male ones. This is the first report of a distinct anatomical sex difference regarding two major components of a key center of motor control. Prenatal sexual differentiation of the striatum may lead to a sexually dimorphic extrapyramidal circuitry, the existence of which, in the adult, is suggested by experimental and clinical data.