Gustatory and Homeostatic Functionsof the Rodent Parabrachial Nucleus

摘要

Previous studies demonstrate that lesions to the rodent parabrachial nucleus (PBN) dis-rupt the formation of gustatory-postingestive associations, while preserving gustatoryand viscerosensory functions. This suggests that the rodent PBN functions essentiallyas an integrative circuit, supporting the conditioning of tastants to postingestive factors.In the case of primates, however, anatomical studies have failed to demonstrate gusta-tory projections from medullary nuclei to PBN. It should therefore be inferred that theprimate PBN lacks the associative functions assigned to its rodent counterpart. More-over, the ability of rodent midbrain doparninergic systems to respond to the activationof palatable tastants depends on the integrity of the gustatory PBN. However, recentstudies demonstrate that caloric palatable compounds do not require taste signalingto produce elevated brain dopamine levels. This raises the possibility that, in rodents,PBN neurons are important for the detection of postingestive effects of nutrients thatoccur independently of gustatory input. If confirmed, such function would assign non-associative roles to the rodent PBN, approximating its functional organization to itsprimate counterpart. We are currently testing this possibility by monitoring the be-havioral responses to caloric glucose solutions in sweet-blind mice having sustainedbilateral lesions to the PBN. Preliminary results indicate that the rodent PBN regulatesnutrient intake even when no gustatory inputs are involved. This favors the assignmentof non-gustatory, homeostatic functions to the rodent PBN during feeding, a concept thatbrings an additional perspective on the rodent versus primate functional discrepancyassociated with the anatomy of this pontine nucleus.