benzimidazol-2-one), either injected intranigrally or given systemically, also elevated striatal dopamine release and facilitated motor activity, confirming that these effects were caused by blockade of endogenous N/OFQ signaling. The inhibitory role played by endogenous N/OFQ on motor activity was additionally strengthened by the finding that mice lacking the NOP receptor gene outperformed wild-type mice on the rotarod. We conclude that NOP receptors in the substantia nigra pars reticulata, activated by endogenous N/OFQ, drive a physiologically inhibitory control on motor behavior, possibly via modulation of the nigrostriatal dopaminergic pathway.

1 The newly discovered neuropeptide nociceptin (NC) has recently been reported to be the endogenous ligand of the opioid-like orphan receptor. Despite its structural similarity to opioids, when injected intracerebroventricularly (i.c.v.) in the mouse, NC exerts a direct hyperalgesic e ect and reverses opioidinduced analgesia. In the present investigation, these two e ects of NC were evaluated under the same experimental conditions; in addition, a pharmacological characterization of the receptor mediating these central e ects of NC was attempted. 2 NC caused a dose dependent (0.1 ± 10 nmol/mouse), naloxone-insensitive reduction of tail withdrawal latency with a maximal e ect of about 50% of the reaction time observed in saline injected mice. In the same range of doses, NC inhibited morphine (1 nmol/mouse) induced analgesia.3 The e ects of the natural peptide were mimicked by NCNH 2 and NC(1 ± 13)NH 2 (all tested at 1 nmol/mouse) while 1 nmol NC(1 ± 9)NH 2 was found to be inactive either in reducing tail withdrawal latency or in preventing morphine analgesia. 4 [Phe 1 c(CH 2 -NH)Gly 2 ]NC(1 ± 13)NH 2 ([F/G]NC(1 ± 13)NH 2 ), which has been shown to antagonize NC e ects in the mouse vas deferens, acted as an agonist, mimicking NC e ects in both the experimental paradigms. In addition, when NC and [F/G]NC(1 ± 13)NH 2 were given together, their e ects were additive. 5 These results demonstrate that both the direct hyperalgesic action and the anti-morphine e ect of NC can be studied under the same experimental conditions in the mouse tail withdrawal assay. Moreover, the pharmacological characterization of the NC functional site responsible for these actions compared with the peripherally active site, indicates the existence of important di erences between peripheral and central NC receptors.

To establish a dominance order, social animals often rely on indicators of fighting to avoid costly aggressive encounters. In some species, individuals use colour patterns to signal their social status. Recent studies claimed that facial markings in the eusocial paper wasp Polistes dominulus are status badges that allow co-foundresses to form a linear hierarchy based on individual quality. Here, we evaluated facial patterns in natural populations of P. dominulus, in its native range, to observe whether the marks reflect overall wasp quality in different contexts. We used the same measures of clypeus patterns used by earlier studies, but did not find that they functioned as status badges. Our analyses showed no evidence that visual markers are related to: (i) size, (ii) probability of surviving winter, (iii) social rank in spring associations, or (iv) health status (assessed by the presence of strepsipteran endoparasites). Size, however, is important. Larger wasps are more likely to survive the winter and to acquire the dominant position in spring associations. Larvae infected with endoparasites become smaller adult wasps. These findings suggest that body size is a reliable quality indicator on which wasps build their social networks, and that clypeus patterning is not involved.

Infection of the paper wasp, Polistes dominulus (Christ), by the strepsipteran parasite Xenos vesparum Rossi results in a dramatic behavioral change, which culminates in colony desertion and the formation of extranidal aggregations, in which up to 98% of occupants are parasitized females. Aggregations formed on prominent vegetation, traditional lek-sites of Polistes males, and on buildings, which were later adopted as hibernating sites by future queens. First discovered by W.D. Hamilton, these aberrant aggregations are an overlooked phenomenon of the behavioral ecology of this intensively studied wasp. For 3 months in the summer of 2000, during the peak of colony development, we sampled 91 extranidal aggregations from seven areas, numbering 1322 wasps. These wasps were parasitized by both sexes of X. vesparum, but males were more frequent from July until mid-August, during the mating season of the parasite. Aggregations were present for days at the same sites (in one case a leaf was occupied for 36 consecutive days) and were characterized by extreme inactivity. After artificial infection, parasitized ''workers'' deserted the nest 1 week after emergence from their cell and before the extrusion of the parasite through the host cuticle. Infected individuals did not work, were more inactive, and did not receive more aggression than did controls. We suggest that early nest desertion and subsequent aggregations by parasitized nominal workers and ''future queens'' is adaptive manipulation of host behavior by the parasite to promote the completion of its life cycle.

]-5-HT over¯ow (EC 50 =64 nM; E max =31% inhibition), but its eect was partially antagonized by 10 mM naloxone. 5 It is concluded that the ORL 1 receptor is the most important presynaptic modulator of neocortical 5-HT release within the opioid receptor family. This suggests that the ORL 1 /nociceptin system may have a powerful role in the control of cerebral 5-HT-mediated biological functions.

Using flow cytometry, the genome sizes of two species of Strepsiptera were studied: that of male Caenocholax fenyesi texensis Kathirithamby & Johnston (Myrmecolacidae) at 108 Mb, which is the smallest insect genome documented to date; and those of male and female Xenos vesparum Rossi (Stylopidae), which are 1C = 130 and 133 Mb, respectively. The genome sizes of the following were analysed for comparative purposes: (a) the Hessian fly, Mayetiola destructor (Say), which was previously reported to be the smallest among insects: the male measured at 1C = 121 Mb and the female at 1C = 158 Mb; and (b) the female parasitic, haplodiploid, microhymenopteran wasp, Trichogramma brassicae Bezdenko, which measured at 1C = 246 Mb. The hosts of the strepsipterans were also measured: male Solenopsis invicta Buren, the red imported fire ant (host of male C. f. texensis), which is 1C = 753.3 Mb, and female Polistes dominulus Christ, the paper wasp (host of X. vesparum), is 1C = 301.4 Mb. Endoreduplication (4C) of the genome of the thorax of the male strepsipteran, and higher levels of endoduplication (4, 8, 16C) in the body of the larger female was observed. In contrast, little or no endoreduplication was observed, either in the Hessian fly, or in the parasitic wasp.

Though the paper wasp genus, Polistes, is well studied, we know little of the incidence of parasitism in this group. Here we present details of 45 nest dissections for 4 species: P. dominulus (Christ), P. gallicus (L.), P. stabilinus Richards and P. carnifex (F.) to detail levels of parasitism of colony members by the obligate parasitic group of insects, the Strepsiptera. All 4 species showed evidence of parasitism among immature members. For 3 species, more than 50 % of inspected nests were parasitized and the levels of parasitism among brood (larvae and pupae) was very high and did not differ significantly between parasitized nests. One species, P. stabilinus, suffered very low levels of parasitism, which may be related to its habitat choice. The number of parasites per host was positively related to the proportion of infected brood (parasite prevalence) and in some cases reached phenomenally high levels, which casts doubt on previously assumed mechanisms of infection for nest-making Hymenoptera, i.e. phoresy. We also document cases of egg parasitism and encapsulation in Polistes nests. Our data show that parasitism levels greatly varied among areas. Finally, the recent debate on the competitive advantage of P. dominulus in its introduced range, USA, has credited an absence of strepsipteran parasites of this species in facilitating its spread. For the first time, we document levels of parasitism for this species in its nature P range and this would appear to corroborate previous claims. We place our work in the context of other studies of parasitism of social insects and posit that the genus Polistes may have much to offer to this field.

Dual probe microdialysis was employed in conscious rats to investigate whether endogenous dopamine is involved in the stimulation of glutamate release in the substantia nigra pars reticulata following striatal NMDA receptor activation. Intrastriatal perfusion with NMDA (1 and 10 lM) facilitated nigral glutamate release (dizocilpine-and tetrodotoxin-sensitive). The D 2 dopamine receptor antagonist raclopride increased spontaneous nigral glutamate release and caused a leftward shift in the NMDA sensitivity, lowering NMDA effective concentrations to submicromolar levels. Conversely, the D 1 antagonist SCH23390 prevented the effect of NMDA (1 lM) and caused a rightward shift in the NMDA sensitivity. It was tested whether the antagonist effects were due to dopamine receptor blockade or increased tone on D 1 /D 2 receptors. SCH23390 prevented the raclopride-induced enhancement of spontaneous but not NMDA-evoked glutamate release while raclopride left unchanged the SCH23390-induced inhibition. The physiopathological relevance of the dopaminergic modulation was strengthened by perfusing NMDA in the dopaminedepleted striatum of hemiparkinsonian rats. Nigral glutamate responsiveness to NMDA was enhanced as with raclopride. We conclude that endogenous striatal dopamine regulates both spontaneous and NMDA-induced nigral glutamate release via an opposite control mediated by D 1 facilitatory and D 2 inhibitory receptors. Alterations of this control may subserve the motor symptoms of Parkinson's disease.