Elsevier

Peptides

Volume 19, Issue 6, June 1998, Pages 999-1005
Peptides

Original Articles
The effects of infusion of arginine vasopressin, oxytocin, or their antagonists into the olfactory bulb upon social recognition responses in male rats

https://doi.org/10.1016/S0196-9781(98)00047-3Get rights and content

Abstract

In the present report, the peptides arginine vasopressin (AVP), oxytocin (OXT) or their respective antagonists were infused bilaterally into the olfactory bulb to assess their effects upon recognition responses. Recognition responses were determined in a social discrimination paradigm and consisted of measuring the amount of investigation directed to either the same (previously exposed) or novel juvenile rats under conditions in which clear recognition responses are either present as tested with a 30 min inter-exposure interval or absent as tested with a 120 min inter-exposure interval. Infusion of AVP or OXT resulted in preserved recognition responses, as tested with a 120 min inter-exposure interval, compared with that observed in vehicle-infused controls. When animals were infused with the AVP or OXT antagonists using two different doses and tested for the display of recognition as tested with the 30 min inter-exposure interval, no effects of these antagonists were obtained with either dose. These results demonstrate that the olfactory bulb represents an additional important central nervous system target site where these peptides can act to preserve social recognition responses. Moreover, our results suggest that the underlying mechanisms by which these peptides function within the olfactory bulb differ as a function of whether they are involved with the display versus preservation of recognition responses.

Section snippets

Animals

Adult male Wistar rats (270–300 g body weight) were used as subjects in the experiments. The animals were caged individually with free access to food and water and were maintained under a natural light-dark cycle.

Cannula implantation and infusion

All animals were implanted bilaterally with guide cannulae (21 gauge, 10 mm long) directed toward the olfactory bulbs (OB). Implantations were performed using a stereotaxic apparatus while the animals were under halothane anesthesia. Coordinates for cannulae implants were 7.0 mm

Results

Figure 1 contains the social discrimination response profiles for control (A, Ringer’s), AVP (B), and OXT (C) infused animals as tested at the 120 min IEI. Control animals showed quite similar, and statistically non-significant investigation scores toward the same versus novel juveniles (t = 1.39, p = 0.195). By contrast, the amount of investigation directed to the novel juveniles was significantly greater than the same juveniles in animals receiving an infusion of either AVP (t = 3.77, p <

Discussion

The data from the I125-AVP infusion into the OB suggest this peptide remains primarily localized within the OB. Notably, under the present conditions of I125-AVP infusion, no activity was observed within the septal area. The significance of this observation is that the AVP infused into the OB would unlikely diffuse in substantial amounts so as to activate the septal area to exert its effects; a site which has been shown to be particularly responsive to the modulatory effects of these peptides 3

Acknowledgements

This work was supported by funds provided by the Deutscher Akademischer Austauschdienst (DAAD) Fellowship Program (DED) and Deutsche Forschungsgemeinschaft (RL). The help of Patrick Lorscher is appreciated.

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