This 11-month study examined rates of encountering dung pellet groups, dung piles and ungulates in gallery forests and non-gallery forests during diurnal surveys in the Loma Mountains Non-Hunting Forest Reserve (LMNHFR) in Sierra Leone, West Africa. These indices of relative abundance were then used to infer relative habitat use by the seven ungulate species on which data were collected. This study also examined the differences in rates of encountering duikers during nocturnal surveys with rates of encountering duikers during diurnal surveys to determine which time of day produces higher rates of encounter, and thereby a more accurate estimate of duiker abundance. The dung of four of the seven species, namely Cephalophus niger, Philantomba maxwelli, Tragelaphus scriptus, and Potamochoerus porcus is encountered at a higher rate in gallery forest than in non-gallery forest. Rates of encountering the dung of three species, C. silvicultor, C. dorsalis and Syncerus caffer nanus, do not differ between forest types. Rates of encountering four species, namely C. niger, P. maxwelli, T. scriptus, and C. silvicultor are higher in gallery forest than in non-gallery forest. Rates of encountering three species, namely C. dorsalis, S. caffer nanus, and P. porcus do not differ between forest types. Rates of encountering duikers ranged from three to six times higher during nocturnal surveys than during diurnal surveys for C. niger and P. maxwelli and 20 times higher for C. dorsalis. Survey timing did not affect the rate of encounter for C. silvicultor. Forest ungulates in the LMNHFR utilize gallery forests regularly. Possible reasons for the higher rates of encounter for six of the species in gallery forests compared with non-gallery forests are access to water, readily available browse resulting from annual fire damage on the periphery and interior of gallery forests, and easy access to cover for ungulates when foraging in adjacent grassland. Given the current rate of forest loss in West Africa, studies examining how forest mammals are able to persist in small forest fragments should be high priority for both government and conservation groups. The findings here give evidence that forest ungulates can and do use small areas of forest. Most importantly, the findings from this study show the global value of the LMNHFR for the conservation of large mammals endemic to the Upper Guinea Forests.

Nous avons étudié les relations anatomiques entre les systèmes de neurotransmission à substance P (SP) et à sérotonine (5-hydroxytryptamine, 5-HT) dans le noyau du raphé dorsal (NRD) du rongeur, afin de mieux comprendre les interactions entre ces systèmes durant la régulation de l’humeur. Le NRD reçoit une innervation SP provenant de l’habenula, et le blocage pharmacologique des récepteurs neurokinine-1 (rNK1) de la SP aurait des effets antidépresseurs. Chez le rongeur, le traitement par les antagonistes des rNK1 s’accompagne d’une désensibilisation des autorécepteurs 5-HT1A de la 5-HT et d’une hausse de l’activité des neurones 5-HT dans le NRD, suggérant des interactions locales entre ces deux systèmes. Dans un premier temps, nous avons démontré par doubles marquages immunocytochimiques en microscopies optique, confocale et électronique, la présence du rNK1 dans une sous-population de neurones 5-HT du NRD caudal. Lors de l’analyse en microscopie électronique, nous avons pu constater que les rNK1 étaient principalement cytoplasmiques dans les neurones 5-HT et membranaires sur les neurones non 5-HT du noyau. Grâce à d’autres doubles marquages, nous avons aussi pu identifier les neurones non-5-HT porteurs de rNK1 comme étant GABAergiques. Nous avons ensuite combiné l’immunomarquage de la SP avec celui du rNK1, dans le but d’examiner les relations entre les terminaisons (varicosités *) axonales SP et les neurones 5-HT (pourvus de rNK1 cytoplasmiques du NRD caudal. En simple marquage de la SP, nous avons pu estimer à 41% la fréquence avec laquelle les terminaisons SP font synapse. Dans le matériel doublement marqué pour la SP et son récepteur, les terminaisons SP ont été fréquemment retrouvées en contact direct ou à proximité des dendrites munies de rNK1 cytoplasmiques, mais toujours éloignées des dendrites à rNK1 membranaires. Pour tester l’hypothèse d’une internalisation soutenue des rNK1 par la SP dans les neurones 5-HT, nous avons ensuite examiné la localisation subcellulaire du récepteur chez le rat traité avec un antagoniste du rNK1, le RP67580. La densité du marquage des rNK1 a été mesurée dans le cytoplasme et sur la membrane des deux types de dendrites (5-HT: rNK1 cytoplasmiques; non 5-HT: rNK1 membranaires). Une heure après une injection unique de l’antagoniste, la distribution du rNK1 est apparue inchangée dans les deux types de neurones (5-HT et non 5-HT). Par contre, après un traitement quotidien de 7 ou 21 jours avec l’antagoniste, nous avons mesuré une augmentation significative des densités cytoplasmique et membranaire du rNK1 dans les neurones 5-HT, sans aucun changement dans les neurones non 5-HT. Ces traitements ont aussi augmenté l’expression du gène rNK1 dans le NRD. Enfin, nous avons mesuré une hausse de la densité membranaire du rNK1 dans les neurones 5-HT, sans hausse de densité cytoplasmique, par suite d’une lésion bilatérale de l’habenula. Ces résultats confortent l’hypothèse d’une activation et d’une internalisation soutenues des rNK1 par la SP dans les neurones 5-HT du NRD caudal. Ils suggèrent aussi que le trafic des rNK1 dans les neurones 5-HT du NRD représente un mécanisme cellulaire en contrôle de l’activation du système 5-HT par les afférences SP en provenance de l’habenula. / We have studied in detail the relationships between substance P (SP) and serotonin (5-hydroxytryptamine, 5-HT) neurotransmission systems in the dorsal raphe nucleus (DRN) of rodents, in order to further our understanding of their interaction during mood regulation. The DRN receives a SP innervation arising from the habenula and, in human, it is known that blockade of the neurokinin-1 receptor (NK1r) of SP by antagonists may have antidepressant effects. In rodents, treatment with NK1r antagonists is known to increase the firing of DRN 5-HT neurons and to induce a desensitization of their 5-HT1A autoreceptors, suggesting local interactions between the SP and 5-HT systems. In a first step, we were able to demonstrate by means of light, confocal, and electron microscopic immunocytochemistry, including double immunolabelings of NK1r and of the biosynthetic enzyme of 5-HT, tryptophane hydroxylase, the presence of NK1r in a subpopulation of 5-HT neurons in the caudal DRN of rat and mouse. After the dual immunolabelings for electron microscopy, we also found that NK1r was mostly cytoplasmic in 5-HT neurons while predominating on the plasma membrane of TPH negative (non 5-HT) neurons. Subsequently, in additionnal double labeling experiments, we were able to identify most if not all non 5-HT dendrites bearing membranous NK1r as GABAergic. In a second step, we combined the immunolabeling of SP with that of NK1r, in order to examine the relationships between SP axon terminals (varicosities *) and the two categories of DRN neurons (5-HT: cytoplasmic NK1r; non 5-HT: membranous NK1r). After single SP labeling, we could estimate the frequency with which SP terminals made synapse at 41%, at least. In the material doubly labeled for SP and NK1r, the SP terminals were often found in close contact or in the immediate proximity of dendrites endowed with cytoplasmic receptor, but never near non 5-HT dendrites bearing membrane bound receptors. To test the hypothesis of a sustained internalization of NK1r in 5-HT neurons, we then tested the effects of RP67580, a selective NK1r antagonist, on the subcellular localization of the receptor. One hour after administration of a single dose, the NK1r distribution was unchanged in both types of dendrites (5-HT and non 5-HT). However, after administration for 7 (subchronic) or 21 (chronic) days, the cytoplasmic and the membrane densities of NK1r were significantly increased in 5-HT dendrites, without any change in non 5-HT dendrites. These treatments also increased NK1r gene expression in the caudal DRN. Lastly, a significant increase in the membrane density of NK1r was measured in the 5-HT neurons, without any increase of the cytoplamic density, following bilateral electrolytic lesioning of the habenula. These results strenghtened the hypothesis of a sustained activation and internalization of NK1r by SP in 5-HT neurons of the caudal DRN. They also suggested that trafficking of NK1r in these cells might represent a cellular mechanism in control of the activation of the 5-HT system by SP afferents from the habebula.

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