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5-HT1A, 5-HT1B and 5-HT2 receptor agonists induce differential behavioral responses in preweanling rat pups
N A Frambes1, C L Kirstein, C A Moody
1Department of Psychology, Suny-Binghamton 13901.
Insights
Serotonin agonists 8-OH-DPAT, ipsapirone, mCPP, and DOI affect behaviors in preweanling rats differently than in neonates. These developmental changes in serotonin receptor function may influence early life behaviors.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- Serotonergic systems play a crucial role in neurodevelopment.
- Understanding the ontogeny of serotonin receptor function is vital for comprehending behavioral development.
Purpose of the Study:
- To investigate the effects of specific serotonin receptor agonists on behaviors in preweanling rats.
- To compare these effects with those observed in neonatal rats to identify developmental changes.
Main Methods:
- Preweanling Sprague-Dawley rats (postnatal day 17-18) were administered various doses of 5-HT1A agonists (8-OH-DPAT, ipsapirone), a 5-HT1B agonist (mCPP), and a 5-HT2 agonist (DOI).
- Behaviors including mouthing, grooming, and limb positioning were assessed in the presence and absence of milk.
- Responses were compared to previously reported data from neonatal rats.
Main Results:
- 8-OH-DPAT decreased mouthing behavior, while ipsapirone, mCPP, and DOI had no effect.
- All four agonists significantly reduced grooming behavior.
- 8-OH-DPAT and mCPP altered limb positioning, causing hindlimb control issues and a hindlimb straddle, respectively.
- Functional responses to these agonists differed between preweanling and neonatal rats.
Conclusions:
- Serotonin receptor-mediated behaviors exhibit significant ontogenetic changes from the neonatal to preweanling period.
- These developmental alterations in serotonergic function may underlie observed changes in behaviors like mouthing and suckling.
- The study highlights the dynamic nature of the developing brain's response to neurotransmitter systems.
Abstract:
Preweanling (postnatal day 17-18) Sprague-Dawley rat pups were tested in both the absence and presence of milk following administration of various doses of the 5-HT1A agonists 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) or ipsapirone, the 5-HT1B agonist 1-(3-chlorophenyl)piperazine (mCPP) or the 5-HT2 agonist 1-(2,5-dimethoxy-4-iodo-phenyl)-2-aminopropane (DOI). 8-OH-DPAT decreased mouthing while ipsapirone, mCPP and DOI had no effect upon this behavior. However, all four agonists significantly decreased grooming. Both 8-OH-DPAT and mCPP produced alterations in limb positioning, with 8-OH-DPAT administration resulting in a poor control of the hindlimbs and mCPP inducing a hindlimb straddle position. These functional responses to 5-HT1A, 5-HT1B and 5-HT2 agonists in preweanling pups vary from those observed previously in neonates. For instance, whereas inhibitory effects of 5-HT1A stimulation on mouthing are observed in both neonatal and preweanling pups, facilitory effects of 5-HT1B and 5-HT2 stimulation are only seen in neonates. These ontogenetic alterations may be related to the previously reported ontogenetic reversal in the effect of serotonergic activation upon mouthing and suckling that occurs during the neonatal to weanling age period.