Gonadotropin-releasing hormone (GnRH) immunoreactive neurons in male mouse lemurs following removal of the vomeronasal organ.

Removal of the vomeronasal organ (VNO) in male mouse lemurs led to an increase in the number of immunoreactive gonadotropin-releasing hormone (GnRH) neurons in the medial preoptic area, compared to control males. No difference was found in the mediobasal hypothalamus. In this primate, which presents a fully functional VNO, the anterior part of the hypothalamus could be the major target for VNO-mediated regulation of GnRH function and the subsequent modulation of chemosensory dependent reproductive behavior.

Behavioral study in the gray mouse lemur (Microcebus murinus) using compounds considered sweet by humans.

This study presents the results from two-bottle preference (TBP) tests performed on the gray mouse lemur (Microcebus murinus), a small Malagasy primate. We found that of 18 compounds considered sweet by humans, M. murinus preferred only six: D-tryptophan, dulcin, fructose, sucrose, SC45647, and xylitol. The animals neither preferred nor rejected acesulfame-K, alitame, aspartame, N-4-cyanophenyl-N'-cyanoguanidineacetate (CCGA), cyanosuosan, cyclamate, monellin, saccharin, suosan, super-aspartame, N-trifluoroacetyl-L-glutamyl-4-aminophenylcarbonitrile (TGC), and thaumatin. Together with previously recorded taste-nerve responses in M. murinus to acesulfame-K, alitame, aspartame, cyclamate, monellin, saccharin, and suosan [Hellekant et al., Chem Senses 18:307-320, 1993b], the current results suggest that these compounds either do not taste sweet to M. murinus or they have an aversive taste component. In this work we also relate these findings to phylogeny.

Olfactory bulbectomy modifies photic entrainment and circadian rhythms of body temperature and locomotor activity in a nocturnal primate.

Studies on rodents have emphasized that removal of the olfactory bulbs modulates circadian rhythmicity. Using telemetric recordings of both body temperature (Tb) and locomotor activity (LA) in a male nocturnal primate, the gray mouse lemur, the authors investigated the effects of olfactory bulbectomy on (1) the circadian periods of Tb and LA in constant dim light condition, and (2) photic re-entrainment rates of circadian rhythms following 6-h phase shifts of entrained light-dark cycle (LD 12:12). Under free-running condition, bulbectomized males had significantly shorter circadian periods of Tb and LA rhythms than those of control males. However, the profiles of Tb rhythms, characterized by a phase of hypothermia at the beginning of the subjective day, and Tb parameters were not modified by olfactory bulbectomy. Under a light-dark cycle, olfactory bulbectomy significantly modified the expression of daily hypothermia, especially by an increase in the latency to reach minimal daily Tb, suggesting a delayed response to induction of daily hypothermia by light onset. Reentrainment rates following both a 6-h phase advance and a 6-h phase delay of entrained LD were also delayed in bulbectomized males. Olfactory bulbectomy led to significant fragmentation of locomotor activity and increased locomotor activity levels during the resting period. The shortening of circadian periods in bulbectomized males could partly explain the delayed responses to photic stimuli since in control males, the longer the circadian period, the better the response to light entrainment. This experiment shows for the 1st time that olfactory bulbs can markedly modify the circadian system in a primate.