CRF-induced excessive grooming behavior in rats and mice
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A J Dunn1, C W Berridge, Y I Lai
1Department of Neuroscience, University of Florida College of Medicine, Gainesville 32610.
Abstract:
We studied the grooming response to lateral ventricle injection of CRF in both rats and mice under similar conditions. One microgram of CRF ICV induced a pronounced increase (3- to 4-fold) in the frequency of self-grooming in rats, but only a much smaller (less than 20%) increase in mice. The minimum effective dose of CRF in rats was 300 ng. Although ACTH1-24 induced less grooming in mice than in rats, the difference in potency did not appear to be sufficient to explain the differences between the effectiveness of CRF in the two species. Whereas ACTH increased all types of grooming scored. CRF increased all forms of grooming except flank scratching with the hind limb. The major effect of CRF was to increase the number of episodes of grooming, whereas ACTH1-24 tended to prolong the length of individual episodes. The excessive grooming induced by ICV CRF was not affected by prior treatment with dexamethasone, suggesting that the increased grooming was not due to secondary release of ACTH from the pituitary. Nevertheless, ICV CRF might induce grooming by releasing MSH/ACTH from cerebral storage sites. CRF-induced grooming, like ACTH-induced grooming, was inhibited by naloxone pretreatment. Despite the small qualitative differences, CRF-induced grooming could be due to secondary release of ACTH.
Insights
Corticotropin-releasing factor (CRF) significantly increases self-grooming in rats but has a minimal effect in mice. This species-specific grooming response suggests complex neural pathways involved in stress and behavior.
Area of Science:
- Neuroendocrinology
- Behavioral Neuroscience
Background:
- Corticotropin-releasing factor (CRF) is a key regulator of the stress response.
- CRF's role in modulating behaviors like grooming is species-dependent.
Purpose of the Study:
- To investigate and compare the effects of intracerebroventricular (ICV) CRF administration on grooming behavior in rats and mice.
- To explore the potential mechanisms underlying CRF-induced grooming, including the involvement of ACTH and opioid pathways.
Main Methods:
- Rats and mice received ICV injections of CRF or ACTH1-24.
- Grooming frequency and patterns were quantified.
- The effects of dexamethasone and naloxone pretreatment were assessed.
Main Results:
- ICV CRF (1 µg) significantly increased grooming frequency in rats (3- to 4-fold) but only minimally in mice (<20%).
- CRF primarily increased grooming episodes, while ACTH1-24 prolonged episode duration.
- CRF-induced grooming was not blocked by dexamethasone but was inhibited by naloxone.
Conclusions:
- CRF elicits a robust grooming response in rats, contrasting with a weak response in mice, indicating species-specific neural processing.
- CRF-induced grooming may involve central ACTH release and opioid pathways, independent of pituitary ACTH.
- These findings highlight species differences in CRF's behavioral effects and suggest complex regulatory mechanisms.