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Ontogeny of renin-induced salt appetite in the rat pup
1Biology Department, University of Pennsylvania, Philadelphia.
Insights
Intracerebroventricular renin injections stimulate salt appetite in young rat pups. This behavior is present from 3 days of age and is distinct from milk intake regulation.
Area of Science:
- Neuroscience
- Physiology
- Endocrinology
Background:
- Salt appetite is a critical behavior for maintaining fluid and electrolyte balance.
- The role of renin and its downstream products in regulating salt intake, particularly in early development, is not fully understood.
Purpose of the Study:
- To investigate the effect of intracerebroventricular renin administration on salt appetite in suckling rat pups.
- To determine the developmental emergence and characteristics of renin-induced salt appetite.
Main Methods:
- Suckling rat pups of varying ages received intracerebroventricular injections of renin.
- Following injections, pups were offered NaCl solutions and milk for intake measurements.
- NaCl concentration preferences were assessed.
Main Results:
- Intracerebroventricular renin significantly increased NaCl solution intake in rat pups 5 hours post-injection.
- Salt appetite was observed as early as 3 days of age, was more pronounced in females, and did not affect milk intake.
- Younger pups (3 days) preferred a 12% NaCl concentration, with acceptable concentrations decreasing in older pups.
Conclusions:
- The brain mechanisms for salt appetite are functional in very young rat pups.
- The neurobiological pathways mediating renin-induced salt appetite are distinct from those controlling thirst (dipsogenic effect).
Abstract:
Intracerebroventricular injections of renin in suckling rat pups increased intake of NaCl solutions when they were orally infused 5 hr after injection. The appetite for saline solution was evident in pups as young as 3 days, was greater in females, and was specific insofar as intake of milk, either by suckling or by oral infusion, was not affected. Three-day-old pups increased intake only to 12% NaCl, the acceptable concentration of NaCl becoming lower in older pups. These results suggest, first, that, as is true for feeding and drinking, the brain mechanism for salt appetite is competent for expression of the behavior in the very young rat pup, and second, that its angiotensinergic neural substrate is distinct from that which mediates the dipsogenic effect of the hormone.