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5-HT1A, 5-HT1B and 5-HT2 receptor agonists induce differential behavioral responses in neonatal rat pups
1Department of Psychology, SUNY-Binghamton, NY 13901.
Insights
Neonatal rat pups show distinct behavioral responses to serotonin receptor agonists. Serotonin 5-HT1A, 5-HT1B, and 5-HT2 receptor subtypes are present and influence behaviors like mouthing and probing.
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- Serotonin (5-HT) plays a crucial role in brain development.
- Understanding the function of specific serotonin receptor subtypes in neonates is essential for comprehending developmental processes.
Purpose of the Study:
- To investigate the presence and function of 5-HT1A, 5-HT1B, and 5-HT2 receptor subtypes in Sprague-Dawley rat pups.
- To determine the differential behavioral effects of selective agonists for these receptor subtypes in neonates.
Main Methods:
- Neonatal Sprague-Dawley rat pups (3-4 days old) were administered selective agonists for 5-HT1A (8-OHDPAT), 5-HT1B (mCPP), and 5-HT2 (DOI) receptors.
- Behavioral responses, including mouthing, probing, behavioral activation, and grooming, were assessed in the presence and absence of milk.
Main Results:
- The 5-HT1A agonist 8-OHDPAT decreased mouthing, increased probing, and enhanced behavioral activation.
- The 5-HT2 agonist DOI and 5-HT1B agonist mCPP increased mouthing and decreased probing.
- mCPP decreased behavioral activation and increased grooming, while DOI increased behavioral activation and induced unusual limb positioning.
Conclusions:
- 5-HT1A, 5-HT1B, and 5-HT2 receptor subtypes are functionally present in the neonate rat.
- Stimulation of these receptor subtypes elicits differential behavioral responses, suggesting distinct roles in neonatal development.
- Developmental changes in the balance of these receptor subtypes may explain previously observed shifts in serotonin's effects on behavior from neonatal to weanling stages.
Abstract:
Sprague-Dawley rat pups at 3-4 days prenatally were tested in both the absence and presence of milk following administration of various doses of either the 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OHDPAT), the 5-HT1B agonist 1-(3-chlorophenyl)piperazine (mCPP), or the 5-HT2 agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Administration of 8-OHDPAT decreased mouthing, increased probing and increased behavioral activation. Conversely, the 5-HT2 agonist DOI and the 5-HT1B agonist mCPP increased mouthing and decreased probing. mCPP and DOI differed in their effects on behavioral activation, with mCPP decreasing and DOI increasing this composite behavioral score. mCPP increased grooming, whereas DOI elicited a characteristic unusual positioning of the limbs. Thus it appears that 5-HT1A, 5-HT1B and 5-HT2 receptor subtypes are present in the neonate and elicit differential behavioral responses upon stimulation with selective agonists. Ontogenetic variations in the balance among these receptor subtypes during development may be related to the ontogenetic reversal that has been previously reported in the impact of serotonin manipulations on mouthing and suckling behavior during the neonatal to weanling age period.