Neurotensin expressing neurons developed earlier than vasoactive intestinal polypeptide and vasopressin expressing neurons in the human suprachiasmatic nucleus

Development of neurotensin (NT), vasoactive intestinal polypeptide (VIP), vasopressin (AVP) and neuropeptide-Y (NPY) expressing neurons was investigated in the human fetal suprachiasmatic nucleus of nine subjects ranging from 20-40 weeks of gestation using immunocytochemistry and morphometry. Results obtained showed that NT expressing neurons developed earlier than VIP, AVP and NPY expressing neurons. Consistent with results obtained from animal studies, we also found VIP expressing neurons were born earlier than AVP expressing neurons. Whether the NT expressing neurons play a role in generating circadian rhythms in the early life of humans needs to be further investigated.     

Effects of gap junction blocker on vasopressin and vasoactive intestinal polypeptide rhythms in the rat suprachiasmatic nucleus in vitro

We examined effects of gap junction blockers, octanol and halothane, on circadian rhythms in the release of arginine-vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) in suprachiasmatic nucleus (SCN) slice cultures of the rat. Circadian rhythms in AVP and VIP release maintained when the SCN culture was treated with octanol for 42 h. However, the release of AVP and VIP showed no circadian rhythms after 7 days incubation with octanol or halothane. Circadian rhythmicity in the two peptide rhythms appeared after the removal of the drug from the culture medium. These findings suggested that the gap junction communication may be involved in intercellular coupling within each subpopulation of AVP or VIP neurons in the SCN.     

Vasoactive intestinal polypeptide neuron changes in the senile rat suprachiasmatic nucleus

The suprachiasmatic nucleus (SCN) is thought to be the main neuronal oscillator underlying circadian rhythmicity of different biological phenomena such as sleep-wakefulness and body temperature. Although numerous studies in old rats showed that circadian organization is clearly disturbed in senescence, no decrease in total SCN cell number has been observed. However, in an earlier study we found a significant decrease of approximately 30% in the number of immunocytochemically-stained vasopressin (VP) neurons in the SCN of the old rat. The aim of the present study was to examine whether another group of SCN neurons, i.e., the vasoactive intestinal polypeptide (VIP) cells, shows age-related changes parallel with disturbances found in sleep/wake parameters. Immunocytochemical staining with antiVIP followed by morphometric analysis revealed a 36% decrease in the number of immunoreactive VIP neurons in the SCN of old rats as compared to young ones. The average size of the remaining VIP cells increased in aged rats. The rapid-eye-movement (REM)-sleep time was negatively correlated with the immunoreactive VIP cell number in the old animals. VP and VIP alterations in the SCN may constitute an anatomical substrate for the circadian disturbances observed in senescence.     

Pregnancy does not alter the response of uterine arteries to vasoactive intestinal polypeptide

In order to provide sufficient nutrients for fetal development, pregnancy is associated with a significant increase in uterine blood flow. Although vasoactive intestinal polypeptide (VIP) is considered to be an important regulator of uterine blood flow it is not known whether endothelium-derived relaxing factors contribute to VIP action in the uterine artery, whether pregnancy alters the effect of VIP in the uterine artery and/or whether VIP interacts with noradrenaline and acetylcholine on the uterine artery and whether pregnancy regulates this possible interaction. In the present study, VIP induced a concentration-dependent relaxation of guinea pig uterine arterial rings, both intact and denuded of endothelium. Pregnancy did not alter the relaxation of uterine artery in response to VIP. In all preparations, addition of N(G)-monomethyl-L-arginine (L-NMMA), indomethacin and diethylcarbamazine did not modify the effect of VIP in uterine arteries. The VIP-receptor complex dissociation constant did not differ significantly between studied vessels, and in all experimental groups the relationship between receptor occupancy and the response was linear, with the receptor reserve (K(A)/EC(50)) close to unity. VIP did not modulate acetylcholine-induced relaxation or noradrenaline-induced contraction in both non-pregnant and pregnant guinea pig uterine arteries. This study has shown that: (i) VIP induces relaxation of guinea pig uterine artery acting as a partial agonist on receptors localized in smooth muscle; (ii) pregnancy does not alter the response of guinea pig uterine arteries to VIP and does not change the receptor affinity for VIP, the efficiency of the receptor coupling or the VIP receptor density; and (iii) VIP does not modulate effects of neurotransmitters on guinea pig uterine arteries and pregnancy is not associated with the changes of VIP-neurotransmitter interaction.     

Regulation of inhibitory synaptic transmission by vasoactive intestinal peptide (VIP) in the mouse suprachiasmatic nucleus

Circadian rhythmicity in mammals is generated by a pair of nuclei in the anterior hypothalamus known as the suprachiasmatic nuclei (SCN), whose neurons express a variety of neuropeptides that are thought to play an important role in the circadian timing system. To evaluate the influence of VIP on inhibitory synaptic transmission between SCN neurons, we used whole cell patch-clamp recording in an acute brain slice preparation of mouse SCN. Baseline spontaneous GABAergic inhibitory postsynaptic currents (IPSCs) varied significantly between regions and across phases, with a greater frequency of IPSCs observed in the dorsomedial region during the early night. Bath-applied VIP caused a significant increase in the frequency of spontaneous inhibitory postsynaptic currents (sIPSC) in a reversible and dose-dependent manner with no effect on the mean amplitude or kinetic parameters. The effect of VIP was widespread throughout the SCN and observed in both ventrolateral (VL) and dorsomedial (DM) regions. In the presence of tetrodotoxin, VIP increased the frequency of miniature IPSCs without affecting the mean magnitude or kinetic parameters. The magnitude of the enhancement by VIP was significantly larger during the day than during the night. Pretreatment with the VIP-PACAP receptor antagonist [Ac-Tyr1, D-Phe2]-GHRF 1-29 or the selective VPAC2 receptor antagonist PG 99-465 completely blocked the VIP-induced enhancement. The effect of VIP appears to be mediated by a cAMP/PKA-dependent mechanism as forskolin mimics, while the PKA antagonist H-89 blocks the observed enhancement of GABA currents. Our data suggest that VIP activates presynaptic VPAC2 receptors to regulate inhibitory synaptic transmission within the SCN and that this effect varies from day to night.     

Calbindin-D28k immunoreactivity in the suprachiasmatic nucleus and the circadian response to constant light in the rat

Recent studies in the hamster have led to the discovery that the expression of the calcium binding protein, calbindin-D28k, is a defining feature of neurons in the suprachiasmatic nucleus involved in the regulation of circadian rhythms by environmental light.(2,18, 19,32) To study further the involvement of calbindin-D28k, we examined the effect of exposure to constant light on calbindin-D28k immunoreactivity in the suprachiasmatic nucleus of intact rats and of rats treated neonatally with the retinal neurotoxin, monosodium glutamate. Exposure to constant light is known to disrupt circadian rhythms in rodents and we found previously that treatment with monosodium glutamate selectively prevents the disruptive effect of constant light on circadian rhythms in rats.(7,9) In the present study we found that exposure to light suppresses calbindin-D28k expression in the ventrolateral retinorecipient region of the suprachiasmatic nucleus of rats and that neonatal treatment with monosodium glutamate blocks the suppressive effect of constant light on calbindin-D28k expression. These findings are consistent with the proposed role of calbindin-D28k in photic signaling in the suprachiasmatic nucleus,(32) and point to the possibility that suppression of calbindin-D28k expression is linked to the mechanism by which constant light disrupts circadian rhythms.     

Changes in vasoactive intestinal peptide and arginine vasopressin expression in the suprachiasmatic nucleus of the rat brain following footshock stress

The neuropeptides, arginine vasopressin (AVP) and vasoactive intestinal polypeptide (VIP) are synthesized by neurons of the suprachiasmatic nucleus (SCN) of the hypothalamus and are important regulators of SCN function. Previous studies have demonstrated that acute exposure to stressors can disrupt circadian activity rhythms, suggesting the possibility of stress-related alterations in the expression of these neuropeptides within SCN neurons. In this study, we examined the effect of intermittent footshock stress on AVP mRNA and heterogeneous nuclear RNA (hnRNA) and VIP mRNA expression in neurons of the SCN. Young adult male Sprague/Dawley rats were subjected to 15 s of scrambled intermittent footshock (0.50 mA pulses, 1 pulse/s, 300 ms duration) every 5 min for 30 min. Animals were sacrificed 75 or 135 min after the onset of stress and brains examined for AVP mRNA and hnRNA, and VIP mRNA using in situ hybridization. Footshock stress increased AVP hnRNA levels at the 75 min time point whereas AVP mRNA was elevated at both the 75 and 135 min time points. In contrast, footshock stress decreased the number of cells expressing VIP mRNA in the SCN without changing hybridization level per cell. These data indicate that the disruptive effect of stress on activity rhythms correlate with alterations in the expression of regulatory peptides within the SCN.     

Motor response of the human isolated colon to capsaicin and its relationship to release of vasoactive intestinal polypeptide

The aim of this study was to obtain indirect evidence of the presence of capsaicin-sensitive afferents in the human colon by studying the motor response to capsaicin of longitudinal strips from the human isolated taenia coli in parallel to the ability of capsaicin or KCl to induce peptide release from the human superfused colon. Capsaicin (1 microM) evoked a relaxation of the taenia, approaching 60-80% of the response to isoprenaline. Tachykinins evoked contractions of the taenia, while calcitonin gene-related peptide induced a relaxation. Neither tachyphylaxis to calcitonin gene-related peptide nor preincubation with an anti-calcitonin gene-related peptide serum did block the response to capsaicin which was also unaffected by tetrodotoxin, apamin, naloxone or an anti-galanin serum. Vasoactive intestinal polypeptide produced a concentration-dependent tetrodotoxin-resistant relaxation which was shifted rightward in the presence of anti-vasoactive intestinal polypeptide serum. The anti-vasoactive intestinal polypeptide serum reduced the response to capsaicin and application of capsaicin prevented the ability of anti-vasoactive intestinal polypeptide serum to block exogenous vasoactive intestinal polypeptide. Capsaicin (1 microM) evoked a significant release of vasoactive intestinal polypeptide-like immunoreactivity from the superfused muscle but not mucosa of the human colon. A significant vasoactive intestinal polypeptide-like immunoreactivity release was also observed in response to KCl (80 mM). KCl but not capsaicin evoked a significant release of neurokinin A-like immunoreactivity from colonic muscle and mucosa. No significant release of either substance P-, neuropeptide Y-, galanin- or calcitonin gene-related peptide-like immunoreactivity was detected in response to capsaicin or KCl although detectable levels of each peptide were evident in tissue extracts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lack of circadian patterns in vasoactive intestinal polypeptide release and variability in vasopressin release in vole suprachiasmatic nuclei in vitro

Organotypic hypothalamic cultures of neonatal rats comprising the suprachiasmatic nuclei (SCN) produce stable 20 h release patterns of vasoactive intestinal polypeptide (VIP) and arginine-vasopressin (AVP). Compared with rats, voles show variably expressed circadian activity patterns. In this study we measured neuropeptidergic release patterns in organotypic SCN cultures of neonatal common voles (Microtus arvalis, n = 6). Slices were prepared at postnatal day 6. After 14 days of incubation, 2 h samples of medium were collected during 50 h. None of the vole SCN slices showed a circadian modulation in VIP release. Peaks in AVP occurred, 20 h apart from each other, in four of six vole SCN slices. These findings contrast with the concurrent release patterns of VIP and AVP in rat SCN slices. The results suggest an independent role of both neuropeptides in the oscillatory output pathways of the circadian pacemaker in the common vole.     

Sexual differences and seasonal variations in vasoactive intestinal peptide immunoreactivity in the suprachiasmatic nucleus of jerboa (Jaculus orientalis).

The sexual differences and the seasonal variation in the vasoactive intestinal peptide (VIP) content of the suprachiasmatic nucleus (SCN) of a desert rodent, the jerboa (Jaculus orientalis) were studied using immunocytochemical techniques. During the period of sexual activity (spring-early summer), the VIP immunoreactivity in the SCN was higher in females than in males. In the period of sexual quiescence (autumn), both males and females exhibited an even more intense VIP immunoreaction in the SCN as compared to spring. However, during this period, the sex-related differences in the VIP content of the SCN observed in spring were no longer detectable. The direct possible influence of sex hormones on the VIP content in the SCN, and the physiological significance of the seasonal variation observed in the VIP immunoreactivity in the SCN in this species remains to be determined.     

Changes in vasoactive intestinal peptide mRNA levels in the rat suprachiasmatic nucleus following p-chlorophenylalanine (PCPA) treatment under light/dark conditions

Photic stimulus and serotonin (5-hydroxytryptamine; 5-HT) are two factors known to regulate vasoactive intestinal peptide (VIP) synthesis in the suprachiasmatic nucleus (SCN). To explore the role of 5-HT in the photic stimulus-induced change in VIP synthesis, we investigated the changes in level of VIP mRNA under a 12 h light/12 h dark cycle following depletion of 5-HT by intraperitoneal administration of p-chlorophenylalanine (PCPA) methyl ester (200 mg/kg concentration) for 3 successive days. To estimate VIP mRNA expression, we performed in situ hybridization using imaging plates combined with microcomputer-based imaging analysis. In light-phase, total signals of VIP mRNA from the PCPA-treated rats showed a signifanct decrease compared with those from the saline-treated control rats. However, in dark-phase, there were no significant decreases between the PCPA-treated rats and the saline-control rats. The present results strongly suggest that 5-HT neuronal inputs to the SCN interfere with the effect of photic stimulus on VIP synthesis at the mRNA level.     

Depression of hypoxic arousal response in adolescent mice following antenatal vasoactive intestinal polypeptide blockade

Late-gestation blockade of vasoactive intestinal polypeptide (VIP) activity in pregnant mice produces discrete morphological abnormalities in the somatosensory cortex of offspring. We investigated the functional implications of this lesion on the behavioural arousal response to moderate hypoxia. Pregnant mice received twice-daily injections of 200 μl saline (control), or saline + 50 μg VIP antagonist (anti-VIP) on embryonic days 17 and 18. Offspring were studied unrestrained at 6–7 weeks after birth, in a bias-flow whole-body plethysmograph during behavioural quiet sleep. Arousal was defined by movement (MVT) lasting >1 s. Hypoxic ventilatory (HVR) and arousal responses were measured during a 5 min exposure to 10 % O₂-3 % CO₂ (hypoxia); peripheral chemoreflex drive was estimated by transient hyperoxia administered at rest and end-hypoxia (Dejours-type test). MVTs increased in all mice during hypoxia, but in anti-VIP mice: (a) MVT onset was delayed (174 ± 90 vs. 108 ± 59 s from the start of hypoxia, anti-VIP vs. control;   P = 0.008  ); and (b) MVTs were less frequent, and total MVT time in hypoxia was less (8 ± 7 vs. 15 ± 9 %;   P = 0.03  ). The HVR, and peripheral drive at rest and end-hypoxia were comparable in control and anti-VIP mice. In conclusion, a significant arousal deficit was evident in anti-VIP mice. This was not associated with obviously deranged peripheral or brainstem-mediated responses to hypoxia during sleep. This may signal a general deficit in the way hypoxic distress is monitored and processed, and arousal initiated and sustained in these mice.     

Distribution of vasoactive intestinal polypeptide in the rat and mouse brain.

The distribution of cell bodies and nerve fibers that combine with antisera to vasoactive intestinal polypeptide (VIP) was studied by immunohistochemistry in combination with radioimmunoassay in the brain of rat and mouse. The highest concentrations (60pmol/g wet wt) of immuno-reactive VIP were found in the cerebral cortex and in certain limbic structures, whereas the concentrations in the basal ganglia, thalamus, lower brain stem, cerebellum and spinal cord were low (<15pmol/g). VIP-immunoreactive cell bodies were found mainly in the cerebral cortex and the limbic system, with the great majority of them in neo- and allocortical areas. In the neocortex the VIP-containing cell bodies were found in layers II-V in all areas. The cells were fusiform or stellate shaped, resembling intracortical and corticocortical association neurones. In the pyriform and entorhinal cortex the cell bodies were located mainly in layer II. In the hippocampal complex VIP-containing cell bodies occurred in both the subiculum, areas CA1 and CA3 and the dentate gyrus. Most of the cells had the appearance of interneurones, some of them probably being identical with basket cells. Of subcortical areas, the amygdala had the largest number of VIP-containing cell bodies; they were numerous in all amygdaloid nuclei except in the central nucleus. Non-cortical areas where there were cell bodies containing VIP included the anterior olfactory nuclei, the bed nucleus of stria terminalis, lateral septum, suprachiasmatic nucleus, superior colliculus, and the mesencephalic periaqueductal gray.VIP-immunoreactive fibres had a distribution which on the whole paralleled that of the cell bodies, suggesting that many of the VIP-containing cells project locally. VIP-containing fibres were numerous in the following areas: the entire neocortex, the pyrifom cortex, the entorhinal cortex, the hippocampal complex, the amygdala (the central nucleus in particular), the anterior olfactory nuclei, the nucleus accumbens, ventral pallidum, bed nucleus of stria terminalis, suprachiasmatic nucleus, medial preoptic nucleus, median eminence, lateral geniculate body, pretectum, superior colliculus, periaqueductal gray, and the lateral parabrachial nucleus. Only few, scattered fibres were seen in other parts of the brain stem, in the striatum, thalamus and spinal cord. The cerebellum was devoid of VIP-containing fibres. VIP-containing neurones seem to form predominantly local projections. In addition, some VIP-containing neurones probably also form long projections, such as descending and transcallosal projections from the cortical cells, and projections from the amygdala to preoptic, hypothalamic and basal forebrain areas.The characteristic telencephalic distribution of the neurones that contain VIP suggests a role for this peptide in cortical and limbic functions.     

Disrupted neuronal activity rhythms in the suprachiasmatic nuclei of vasoactive intestinal polypeptide-deficient mice

Vasoactive intestinal polypeptide (VIP), acting via the VPAC(2) receptor, is a key signaling pathway in the suprachiasmatic nuclei (SCN), the master clock controlling daily rhythms in mammals. Most mice lacking functional VPAC(2) receptors are unable to sustain behavioral rhythms and lack detectable SCN electrical rhythms in vitro. Adult mice that do not produce VIP (VIP/PHI(-/-)) exhibit less severe alterations in wheel-running rhythms, but the effects of this deficiency on the amplitude, phasing, or periodicity of their SCN cellular rhythms are unknown. To investigate this, we used suction electrodes to extracellularly record multiple- and single-unit electrical activity in SCN brain slices from mice with varying degrees of VIP deficiency, ranging from wild-type (VIP/PHI(+/+)) to heterozygous (VIP/PHI(+/-)) and VIP/PHI(-/-) animals. We found decreasing proportions of rhythmic cells in SCN slices from VIP/PHI(+/+) ( approximately 91%, n = 23) through VIP/PHI(-/+) ( approximately 71%, n = 28) to VIP/PHI(-/-) mice (62%; n = 37) and a parallel trend toward decreasing amplitude in the remaining rhythmic cells. SCN neurons from VIP/PHI(-/-) mice exhibited a broad range in the period and phasing of electrical rhythms, concordant with the known alterations in their behavioral rhythms. Further, treatment of VIP/PHI(-/-) slices with a VPAC(2) receptor antagonist significantly reduced the proportion of oscillating neurons, suggesting that VPAC(2) receptors still become activated in the SCN of these mice. The results establish that VIP is important for appropriate periodicity and phasing of SCN neuronal rhythms and suggest that residual VPAC(2) receptor signaling promotes rhythmicity in adult VIP/PHI(-/-) mice.     

Per1 and Per2 gene expression in the rat suprachiasmatic nucleus: circadian profile and the compartment-specific response to light

Expression profiles of rPer1 and rPer2 messenger RNAs, rat homologues of the Drosophila clock gene period, were examined in the rat suprachiasmatic nucleus, a main locus of circadian oscillation, with special reference to the topographical compartmentation of the suprachiasmatic nucleus. Quantitative in situ hybridization of rPer1 and rPer2 messenger RNAs showed a robust circadian rhythm in the suprachiasmatic nucleus, with a characteristic peak/trough profile in each gene: the peak of rPer1 messenger RNA was in the daytime and that of rPer2 messenger RNA was at the transition time of day to night in both light-dark and constant dark conditions. Light exposure at circadian time 16 increased both rPer1 and rPer2 messenger RNAs in the suprachiasmatic nucleus. In a detailed histological analysis, we found that light exposure at circadian time 16 induced the expression of rPer1 and rPer2 genes in neurons limited to the ventrolateral part of the suprachiasmatic nucleus, although the usual circadian rPer1 and rPer2 messenger RNA oscillation in light-dark and constant dark conditions occurred strongly in neurons in the dorsomedial part but weakly in neurons in the ventrolateral part of the suprachiasmatic nucleus. These rPer expression profiles indicate that the two major subpopulations of neurons in the suprachiasmatic nucleus play different roles in the generation of circadian rhythm: a strong autonomous expression ability with no light response in dorsomedial neurons and a strong light responsiveness with a weak autonomous expression in ventrolateral neurons.     

Environmental light and suprachiasmatic nucleus interact in the regulation of body temperature

The mammalian biological clock, located in the suprachiasmatic nucleus (SCN), is crucial for circadian rhythms in physiology and behavior. However, equivocal findings have been reported on its role in the circadian regulation of body temperature. The goal of the present studies was to investigate the interaction between the SCN and environmental light in the regulation of body temperature. All recordings were performed by telemetry in free moving male Wistar rats. Firstly, we demonstrated an endogenous circadian rhythm in body temperature independent of locomotor activity. This rhythm was abolished by stereotactic lesioning of the SCN. Secondly, we demonstrated a circadian phase-dependent suppressive effect of light ('negative masking') on body temperature. Light suppressed body temperature more at the end of the subjective night (circadian time [CT] 22) than in the middle (CT 6) and at the end (CT 10) of the subjective day. This circadian-phase dependent suppression was not demonstrated in SCN-lesioned animals. Surprisingly, after half a year of recovery from lesioning of the SCN, light regained its suppressing action on body temperature, resulting in a daily body temperature rhythm only under light-dark conditions. In contrast to body temperature, light could not substantially mimic a daytime inhibitory SCN-output in the regulation of heart rate and locomotor activity. The present results suggest that, after lesioning of the SCN as main relay station for the immediate body temperature-inhibition by light, secondary relay nuclei can fully take over this function of the SCN. These findings provide a possible explanation for the controversy in literature over the question whether the SCN is required for the diurnal rhythm in body temperature. Furthermore, they show that light may have an acute effect on behavior and physiology of the organism via the SCN, which extends beyond the generally acknowledged effect on melatonin secretion.     

Down-regulation of vasoactive intestinal polypeptide receptor expression in atopic dermatitis

BACKGROUND: Receptors for vasoactive intestinal polypeptide (VIP) have recently been suggested to play a key role in immunomodulation with genetically modified mice. However, it is not known whether changes in receptor gene regulation are involved in the pathogenesis of human immune disorders. OBJECTIVE: We studied the expression of VPAC(2) in acute lesions of the human immune disease atopic dermatitis. METHODS: By using nonradioactive in situ hybridization, quantitative immunohistochemistry, RT-PCR, and gene array studies, the expression status of VPAC(2) was assessed in atopic dermatitis and control tissues and in the human mast cell line HMC-1. RESULTS: In situ hybridization and immunohistochemistry demonstrated VPAC(2) mRNA and protein expression in human mast cells surrounded by VIP positive nerve fibers. Gene array experiments and RT-PCR studies showed high levels of VPAC(2) mRNA expression in mast cells that were increased compared to other receptors such as VPAC(1) or VIP in the human mast cell line HMC-1. Stimulation of HMC-1 cells led to a downregulation of VPAC(2). Similarly, quantitative immunohistochemistry for VPAC(2) in acute atopic dermatitis lesions showed a significantly decreased VPAC(2) immunoreactivity in mast cells. CONCLUSION: The downregulation of VPAC(2) in human mast cells in acute lesions of atopic dermatitis suggests a role of this G-protein;coupled receptor in the pathophysiology of the disease.     

Circadian entrainment to temperature,but not light,in the isolated suprachiasmatic nucleus

The suprachiasmatic nucleus (SCN) is the master pacemaker that drives circadian rhythms in mammalian physiology and behavior. The abilities to synchronize to daily cycles in the environment and to keep accurate time over a range of physiologic temperatures are two fundamental properties of circadian pacemakers. Recordings from a bioluminescent reporter (Per1-luc) of Period1 gene activity in rats showed that the cultured SCN entrained to daily, 1.5 degrees C cycles of temperature, but did not synchronize to daily light cycles. Temperature entrainment developed by 1 day after birth. Light cycles failed to affect the isolated SCN of rats aged 2 to 339 days. Entrainment to a 3-h shift in the warm-cool cycle was possible in <3 days with 3 degrees C cycles. Importantly, Per1-luc expression in vitro was similar to that seen in vivo where peak expression occurs approximately 1 h prior to the daily increase in temperature. In addition, the firing rate of individual mouse SCN neurons continued to express near 24-h rhythms from 24-37 degrees C. At lower temperatures, the percentage of rhythmic cells was reduced, but periodicity was temperature compensated. The results indicate that normal rhythms in brain temperature may serve to stabilize rhythmicity of the circadian system in vivo and that temperature compensation of this period is determined at the level of individual SCN cells.     

Developmental changes in vasoactive intestinal polypeptide immunoreactivity in the human paravertebral ganglia

Vasoactive intestinal polypeptide (VIP) belongs to the glucagon-secretin family of polypeptides and possesses numerous functions. Its existence in the mammalian central and peripheral nervous system has been widely documented. However, there are no reports on the developmental aspects of VIP-like immunoreactivity (VIP-IR) in the human postganglionic sympathetic neurons. In this study the availability and distribution of vasoactive intestinal polypeptide has been localized in human stellate ganglia neurons and nerve fibers from neonates, children and adults using the immunohistochemical method. In neonatal ganglia VIP-immunoreactive postganglionic neurons were revealed in a marked population compared to others age-groups. These nerve cells are both small and large in size and are distributed in small clusters or singly in the area of ganglia sections. In children, VIP-IR in ganglionic neurons decreases. In adult stellate ganglia, VIP-immunoreactive postganglionic neurons rarely occur. In ganglia of an individual human only varicosities of VIP-positive nerve fibers were observed. These results provide the age-dependent reduction of VIP-like immunoreactivity in human stellate ganglia neurons and suggest the different role of this peptide in the function of sympathetic ganglia neurons with age.     

Effect of vasoactive intestinal polypeptide on cerebral blood flow in the goat

The effect of vasoactive intestinal polypeptide (VIP) on the cerebral blood flow was investigated in the goat. An electromagnetic flow probe was placed around the internal maxillary artery for continuous measurement of ipsilateral blood flow. Intraarterial injection of VIP resulted in a dose-dependent increase in the cerebral blood flow. The effect was not antagonized by any of the antagonists atropine, propranolol, phentolamine and naloxone administered intraarterially 1 min before VIP. It is discussed that VIP may play a physiological role in the local blood flow regulation in the CNS.