Autoradiographic localization of receptors for neuropeptide Y (NPY) in the brain of broiler and leghorn chickens (Gallus domesticus)

Comparisons of insulin related parameters in commercial-type chicks: Evidence for insulin resistance in broiler chicks

The aim of this study is to elucidate whether insulin acts differentially within the central nervous system (CNS) of two types of commercial chicks to control ingestive behavior. Male layer and broiler chicks (4-day-old) were intracerebroventricularly (ICV) injected with saline or insulin under satiated and starved conditions. Feed intake was measured at 30, 60 and 120 min after treatment. Secondly, blood and hypothalamus were collected from both chick types under ad libitum feeding and fasting for 24 h. Plasma insulin concentration was measured by time-resolved fluoro-immunoassay. Hypothalamic insulin receptor mRNA expression levels were measured by quantitative RT-PCR. The ICV injection of insulin significantly inhibited feed consumption in layer chicks when compared with saline (P<0.05), but not broiler chicks (P>0.1). Plasma insulin concentration of both chick types significantly decreased following 24 h of fasting, while insulin concentrations in the broiler chicks were significantly higher compared to the layers fed under ad libitum conditions. Hypothalamic insulin receptor mRNA expression levels were significantly lower (P<0.05) in broiler chicks than in layer ones under ad libitum feeding. Feed deprivation significantly decreased insulin receptor mRNA levels in layer chicks (P<0.01), but not in broiler chicks (P>0.1). Moreover, plasma insulin concentrations correlated negatively with hypothalamic insulin receptor protein expression in the two types of chicks fed ad libitum (P<0.05). These results suggest that insulin resistance exists in the CNS of broiler chicks, possibly due to persistent hyperinsulinemia, which results in a down-regulation of CNS insulin receptor expression compared to that in layer chicks.

Immunohistochemical distribution of neuropeptide Y in the mesencephalon and rhombencephalon of carp, Cyprinus carpio L. (Cyprinidae: Teleostei)

The localization of neuropeptide Y (NPY)-immunoreactive elements was investigated in the mesencephalon and rhombencephalon of carp, Cyprinus carpio, by using antisera raised against porcine NPY and the immunoperoxidase technique. Concurrently, to identify the distribution of NPY-immunoreactivity, we developed an atlas of the studied areas based on Nissl-stained sections. The NPY-immunoreactive (NPY-ir) elements were located in many zones of the mesencephalon and rhombencephalon. In the mesencephalon, positive fibers were the most abundant elements while neurons were scarce. The rhombencephalon rostral part was characterized by a low to moderate fiber density, distributed in the ventro-medial and ventro-lateral region. Differently the caudal part of the rhombencephalon exhibited several NPY-ir elements. In particular, a high density of immunoreactivity was located in the gustatory area at the level of the nucleus (n.) originis nervi glossopharyngei, in the n. nervi vagi, and in the vagal lobe. The latter can be considered a valid neuroanatomical model for the study of gustatory signal processing in vertebrates. Our results regarding the primary gustatory centers give neuroanatomical support to the view that NPY may act as a neurotransmitter and/or a neuromodulator in a wide neural network for feeding behavior control.

Sex-peptides bind to two molecularly different targets in Drosophila melanogaster females

Sex-Peptide (SP) and the peptide DUP99B elicit two postmating responses in Drosophila melanogaster females: receptivity is reduced and oviposition is increased. Both are synthesized in the male genital tract and transferred into the female during copulation. To elucidate their function, we characterized the binding properties of SP and DUP99B in females. Cryostat sections of adult females were incubated with alkaline phosphatase (AP)-tagged peptides. In virgin females, both peptides have specific target sites in the nervous system and in the genital tract. The binding pattern is almost identical for both peptides. Incubation of sections of mated females confirm that some of these target sites correspond to the in vivo targets of the two peptides. Neuronal binding is dependent on an intact C-terminal sequence of SP, binding in the genital tract is less demanding in terms of amino acid sequence requirement. On affinity blots the AP-SP probe binds to membrane proteins extracted from abdomen and head plus thorax, respectively. The binding proteins in the nervous system and the genital tract differ in their molecular properties. Calculation of dissociation constants (K(d)), and also determination of the minimal peptide concentrations necessary for binding, indicate that SP is the more important peptide inducing the postmating responses. Our results suggest that binding of SP in the nervous system is responsible for eliciting the postmating responses, whereas binding in the genital tract reflects the presence of a peptide transporter.

Autoradiographic distribution of neuropeptide Y binding sites in the brain of the carp Cyprinus carpio L. (Cyprinidae, Teleostei)

The present study reports the distribution of neuropeptide Y (NPY)-binding sites in the brain of the adult carp Cyprinus carpio L. Radioiodinated NPY was used as tracer in the autoradiographic procedure. The NPY-binding sites (NPY-bs) were widely distributed in the carp brain. Generally, a good match was observed between the distribution of NPY-bs and the distribution of NPY-immunoreactive (NPY-ir) elements previously reported in the forebrain of the carp. Low to moderate concentration of NPY-bs were found in the telencephalon, this finding indicates that NPY may play a role in the processing of olfactory inputs and in more complex behaviours like spatial learning acquisition and retention, whose importance could correlated with similar results obtained in mammals. Moreover, in the rhombencephalon, the presence of NPY-bs at level of lobus vagus and the lobus facialis suggests that NPY may be implicated in food-seeking behaviour and swallowing reflex.

The distribution of neuropeptide Y gene expression in the chicken brain

Neuropeptide Y (NPY) is demonstrated to play an important role in central control of voluntary feed intake (FI) of a variety of species. The commercial broiler chicken has been intensively selected over generations for increased body weight, achieved largely through increased FI. This has resulted in a contemporary animal that does not regulate FI to maintain energy balance, and represents a model for hyperphagia and obesity if allowed unrestricted access to feed. In the present study, the distribution of NPY mRNA was mapped in the brain of juvenile, broiler-strain chicken, and results interpreted in the context of previous data for strains that do not exhibit hyperphagia. NPY mRNA was widely distributed in the broiler brain, and highly expressed in the hippocampus, nucleus commissurae pallii, infundibular hypothalamic nucleus, nucleus pretectalis pars ventralis and neurons around the nucleus rotundus. Moderately labeled neurons were found in the lateral septal organ, nucleus periventricularis hypothalamus and nucleus paraventricularis magnocellularis. The pallium exhibited only sparse labeling. Generally, the distribution of cell groups expressing NPY mRNA was consistent with those regions exhibiting NPY immunoreactivity, and also matches the distribution of receptor binding sites reported in the literature for the chicken brain. This suggests that NPY may be involved in functions controlled by these regions. The observation of NPY gene expression in brain regions involved in appetite regulation is consistent with the recognized importance of NPY in FI regulation in a variety of species, and with the chronic hyperphagia, characteristic of the broiler.

Anatomical distribution of NPY-like immunoreactivity in the domestic chick brain (Gallus domesticus)

Neuropeptide Y-immunoreactive (NPY-ir) fibers and neurons in the brain of the domestic chick (Gallus domesticus) were described using an immunohistochemical technique. NPY-ir neurons were seen in the lobus parolfactorius; hyperstriatum, neostriatum, paleostriatum, and archistriatum; hippocampal and parahippocampal areas; dorsolateral corticoid area; piriform cortex; two thalamic areas contiguous to the n. rotundus; n. dorsolateralis anterior thalami, pars lateralis, and pars magnocellularis; n. periventricularis hypothalami; n. paraventricularis magnocellularis; regio lateralis hypothalami; n. infundibuli; inner zone of the median eminence; dorsal and lateral portions of the n. opticus basalis; n. raphes; and n. reticularis paramedianus. NPY-ir fibers were seen throughout the entire chick brain, but were more abundant in the hypothalamus where they formed networks and pathways. They were also observed in some circumventricular organs. The anatomical data of the present study regarding the distribution of NPY ir in the chick brain, together with the physiological findings of other studies, suggest that NPY plays a key role in the regulation of the neuroendocrine, vegetative, and sensory systems of birds by acting as a neuromodulator and/or neurotransmitter.

Chicken neuropeptide Y receptor Y2: structural and pharmacological differences to mammalian Y2(1)

Here we report the molecular cloning of the chicken (Gallus gallus) neuropeptide Y (NPY) receptor Y2, the first non-mammalian Y2 receptor. It displays 75-80% identity to mammalian Y2 and has a surprisingly divergent cytoplasmic tail. Expression of the receptor protein in a cell line showed that the receptor did not bind the mammalian Y2 selective antagonist BIIE0246. Furthermore, porcine [Leu(31), Pro(34)]NPY, which binds poorly to mammalian Y2, exhibited an unexpectedly high affinity for chicken Y2. In situ hybridisation revealed expression in the hippocampus. Thus, the chicken Y2 receptor exhibits substantial differences with regard to sequence and pharmacological profile in comparison to mammalian Y2 receptors, while the expression pattern in the central nervous system resembles that observed in mammals.

Hypothalamic neuropeptide Y mRNA is increased after feed restriction in growing broilers

As part of an approach to uncover the brain mechanisms underlying the regulation of energy balance in broiler chickens, we investigated the possible role of neuropeptide Y (NPY). The NPY gene expression was measured in the hypothalamus of birds from a standard Ross male line and a Ross relaxed line. Both lines are derived from the same founder stock, but the relaxed line has not been selected for rapid growth since 1976. Birds of each line consumed feed either ad libitum or according to a standard commercial restricted feeding program. All groups of birds were killed at an average body weight of 2.4 kg. The NPY mRNA levels were significantly increased (P < 0.0001) in feed-restricted birds of both lines relative to ad libitum controls. No significant differences were detected between the lines. These results show that NPY gene expression in the broiler hypothalamus is sensitive to changes in energetic status, as it is in mammals. However, the maintenance of selection pressure for high growth rate is not associated with altered hypothalamic NPY mRNA levels in the ad libitum or restricted state.