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Brainstem serotonergic hyperinnervation modifies behavioral supersensitivity to 5-hydroxytryptophan in the rat.
M R Pranzatelli1, Y Y Huang, A M Dollison
1Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY 10032.
Brain Research. Developmental Brain Research
|November 1, 1989
Summary
Intracisternal or intraperitoneal 5,7-dihydroxytryptamine (5,7-DHT) lesions in rat pups induced behavioral supersensitivity to 5-hydroxytryptophan (5-HTP). Intraperitoneal injections led to enhanced shaking, while intracisternal injections caused more forepaw myoclonus and head weaving.
Area of Science:
- Neuroscience
- Pharmacology
- Behavioral Science
Background:
- 5,7-dihydroxytryptamine (5,7-DHT) is a neurotoxin used to lesion serotonin (5-HT) neurons.
- 5-hydroxytryptophan (5-HTP) is a precursor to serotonin and can evoke specific behavioral syndromes.
- Understanding the long-term effects of 5,7-DHT administration routes on serotonin system function and behavior is crucial.
Purpose of the Study:
- To investigate the differential effects of intracisternal (i.c.) versus intraperitoneal (i.p.) 5,7-DHT administration on rat pup behavior and serotonin system integrity.
- To assess long-term behavioral supersensitivity to 5-HTP following 5,7-DHT-induced lesions.
- To correlate neurochemical changes with observed behavioral differences.
Main Methods:
- Rat pups received i.c. or i.p. injections of 5,7-DHT or saline.
- Animals were challenged with 5-HTP at 2 and 14 weeks post-lesioning to assess behavioral responses.
- Serotonin (5-HT) and 5-hydroxyindole acetic acid (5-HIAA) levels were measured in various brain regions and the spinal cord.
Main Results:
- Both i.c. and i.p. 5,7-DHT lesions induced behavioral supersensitivity to 5-HTP.
- Intraperitoneal 5,7-DHT lesions resulted in significantly greater shaking behavior, whereas intracisternal lesions led to more forepaw myoclonus and head weaving.
- Serotonin depletions were observed in multiple brain regions, with notable differences in brainstem 5-HT concentrations between i.c. and i.p. routes at 14 weeks.
Conclusions:
- The route of 5,7-DHT administration significantly influences the pattern of behavioral supersensitivity to 5-HTP, suggesting distinct neuroadaptive mechanisms.
- Brainstem 5-HT hyperinnervation following i.p. 5,7-DHT may modulate the functional consequences of serotonin system injury.
- Dysregulation of presynaptic autoregulation or receptor sensitivity likely contributes to the observed behavioral supersensitivity.