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Stimulation-induced ingestion in neonatal rats
Insights
Electrical stimulation of the medial forebrain bundle (MFB) in neonatal rats elicited organized behaviors, with milk enhancing ingestion and activity in younger pups. Older pups showed age-dependent behavioral changes and milk-induced inhibition of non-ingestive actions.
Area of Science:
- Neuroscience
- Developmental Psychology
- Animal Behavior
Background:
- Neonatal rat behavior is complex and influenced by various stimuli.
- The medial forebrain bundle (MFB) is crucial for motivated behaviors.
- Understanding early behavioral organization is key to developmental neuroscience.
Purpose of the Study:
- To investigate the effects of medial forebrain bundle (MFB) electrical stimulation on neonatal rat behavior.
- To determine the role of milk in modulating MFB-stimulated behaviors in rat pups.
- To assess age-dependent changes in behavioral responses to MFB stimulation.
Main Methods:
- Rat pups aged 3, 6, 10, and 15 days received MFB electrical stimulation.
- Stimulation was delivered as 500 ms pulse trains in the presence of milk.
- Behavioral responses, including ingestion and activity levels, were recorded over 30-min tests.
Main Results:
- Stimulated pups ingested more milk than controls at 3, 6, and 10 days, but not 15 days.
- MFB stimulation increased activity and elicited organized behaviors (mouthing, licking, gaping, stretching, lordosis) in pups up to 10 days.
- Milk augmented stimulation effects, increasing all behaviors in 3-day-olds and channeling older pups towards ingestion, while inhibiting incompatible behaviors like lordosis.
Conclusions:
- Neonatal rats exhibit significant behavioral organization elicited by MFB stimulation.
- Milk acts as a modulator, enhancing ingestive behaviors and influencing activity levels in a dose- and age-dependent manner.
- MFB stimulation reveals age-related shifts towards goal-directed behaviors, particularly ingestion, in developing rats.
Abstract:
Rat pups, 3, 6, 10 and 15 days old, received 500 ms pulse trains of electrical stimulation to the medial forebrain bundle (MFB) at the level of the lateral hypothalamus in the presence of milk. Pups receiving stimulation ingested more milk than littermate controls during a 30-min test at 3, 6 and 10 days of age. Day 15 pups did not. Stimulated pups through day 10 were more active than controls and exhibited the organized behaviors of mouthing, licking, gaping, stretch and even lordosis. Stimulated pups that ingested more milk continued to show increased activity through the 30-min test period, while the activity of control pups demonstrated a satiety effect. Milk augmented the activation of stimulation alone, increasing the incidence of all behaviors in 3-day-old pups and channelled the behavior of older pups into ingestion. Behaviors incompatible with ingestion such as lordosis were selectively inhibited by the presence of milk in stimulated day 10 pups. These results suggest a high degree of behavioral organization in neonatal rats than can be elicited by MFB stimulation and that becomes more goal-directed with age.