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5-HT1A receptor activity disrupts spontaneous alternation behavior in rats
Phillip J Seibell1, Jack Demarest, Dennis E Rhoads
1Department of Biology, Monmouth University, West Long Branch, NJ 07764, USA.
Abstract:
Agonists selective for three different serotonin (5-HT) receptor subtypes were tested for the ability to disrupt spontaneous alternation behavior (SAB) in the CD strain of rats. Rats were scored for alternation or repetition in their choice of arms of a T-maze equally baited with chocolate milk. Compared with vehicle controls, the 5-HT(1A) agonist 8-hydroxy-dipropylaminotetraline (8-OH-DPAT; 2 mg/kg) significantly (P<.0001) increased repetitive choices (disrupted SAB). In contrast, intraperitoneal injections with the 5-HT(2) agonist R-(-)-dimethoxyiodophenylaminoethane (DOI; 1 mg/kg) or the 5-HT(3) agonist N-methyl quipazine (NMQ; 3 mg/kg) had no significant effect on SAB in CD rats. Onset of vicarious trial and error (VTE) behavior prolonged the time required for each rat to select an arm of the T-maze when injected with either 8-OH-DPAT (P<.0001) or buspirone (1-2 mg/kg), a 5-HT(1A) partial agonist. The disruption of SAB and the induction of VTE behavior were reversible with behavioral scores returning to preinjection levels within 48 h after injections. The disruption of SAB by 8-OH-DPAT was also seen with the Long-Evans rat strain. The results extend the use of the SAB model and point to a specific role of 5-HT(1A) receptors in the induction of repetitive behavioral patterns.
Insights
The serotonin 5-HT(1A) agonist 8-hydroxy-dipropylaminotetraline (8-OH-DPAT) disrupts spontaneous alternation behavior (SAB) in rats, causing repetitive choices. This effect is specific to 5-HT(1A) receptors and is reversible.
Area of Science:
- Neuroscience
- Behavioral Pharmacology
Background:
- Serotonin (5-HT) receptors are implicated in various cognitive functions.
- Spontaneous alternation behavior (SAB) in a T-maze is a measure of spatial working memory and exploratory behavior in rodents.
Purpose of the Study:
- To investigate the role of specific serotonin (5-HT) receptor subtypes in modulating spontaneous alternation behavior (SAB).
- To determine if agonists for 5-HT(1A), 5-HT(2), or 5-HT(3) receptors affect SAB in rats.
Main Methods:
- Rats (CD strain) were tested in a T-maze for spontaneous alternation behavior (SAB).
- Selective agonists for 5-HT(1A) (8-hydroxy-dipropylaminotetraline; 8-OH-DPAT), 5-HT(2) (R-(-)-dimethoxyiodophenylaminoethane; DOI), and 5-HT(3) (N-methyl quipazine; NMQ) were administered.
- Behavioral changes, including repetitive choices and vicarious trial and error (VTE) behavior, were quantified.
Main Results:
- The 5-HT(1A) agonist 8-OH-DPAT significantly increased repetitive choices, disrupting SAB (P<.0001).
- 5-HT(2) agonist DOI and 5-HT(3) agonist NMQ had no significant effect on SAB.
- 8-OH-DPAT and the 5-HT(1A) partial agonist buspirone induced vicarious trial and error (VTE) behavior.
- Behavioral disruptions were reversible within 48 hours and observed in both CD and Long-Evans rat strains.
Conclusions:
- Serotonin 5-HT(1A) receptors play a specific role in the induction of repetitive behavioral patterns.
- The SAB model is a sensitive tool for evaluating the effects of serotonergic agents on cognitive processes.
- Selective 5-HT(1A) receptor activation disrupts spatial alternation and induces VTE behavior.