Age-related changes on marking, marking-like behavior and the scent gland in adult Mongolian gerbils (Meriones unguiculatus)

Age affects over-marking of opposite-sex scent marks in meadow voles, Microtus pennsylvanicus

Models of age-related effects on behavior predict that among short-lived species younger adults are more attractive and attracted to opposite-sex conspecifics than are older adults, whereas the converse is predicted for long-lived species. Although most studies of age-related effects on behavior support these predictions, they are not supported by many studies of scent marking, a behavior used in mate attraction. Over-marking, a form of scent marking, is a tactic used by many terrestrial mammals to convey information about themselves to opposite-sex conspecifics. The present study tested the hypothesis that the age of meadow voles, Microtus pennsylvanicus; a microtine rodent, affects their over- and scent marking behaviors when they encounter the marks of opposite-sex conspecifics. Sex differences existed in the over-marking behavior of adult voles among the three different age groups that were tested. Male voles that were 5-7 mo-old and 10-12 mo-old over-marked a higher proportion of the marks of females than did 2-3 mo-old male voles. Female voles that were 2-3 mo-old, 5-7 mo-old, and 10-12 mo-old over-marked a similar number of marks deposited by male voles. Overall, the data were not consistent with models predicting the behavior of short-lived animals such as rodents when they encounter the opposite sex. The differences in over-marking displayed by older and younger adult male voles may be associated with life history tradeoffs, the likelihood that they will encounter sexually receptive females, and being selected as mates.

Muscarinic receptor changes in the gerbil thalamus during aging

Here we studied muscarinic receptors in the gerbil thalamus at 8 different ages - from 6 to 36 months - using receptor and functional autoradiography. The pharmacological profile inhibiting [(3)H]N-methyl scopolamine ([(3)H]NMS) binding with 50 and 200 nM pirenzepine, 30 nM pFHHSiD and 100 nM AF-DX 116 revealed the predominance of the M(2) muscarinic subtype in the thalamic nuclei studied, mainly in the anteroventral, anteromedial and paraventricular thalamic nuclei. These data correlated with the highest [(35)S]guanylyl-5'-O-(gamma-thio)-triphosphate ([(35)S]GTP gamma S) binding induced in these nuclei by the muscarinic agonist oxotremorine in functional autoradiographic assays. Significant aging-dependent increases in the functional response in these three nuclei were observed, but only the anteroventral and anteromedial thalamic nuclei showed aging-dependent increases in [(3)H]NMS binding. Since these nuclei exert relevant functions, in which cholinergic pathways are involved and acetylcholine release is reported to decrease during aging, we suggest that the anteroventral and anteromedial thalamic nuclei would play critical roles in the cholinergic transmission that require compensatory mechanisms during the aging process and that are not observed in other thalamic nuclei.