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TRH-induced behavioral arousal in developing rats pretreated with 6-hydroxydopa
Insights
Thyrotropin releasing hormone (TRH) affects behavior in developing rats. Neonatal 6-OHDOPA treatment potentiates TRH
Area of Science:
- Neuroscience
- Developmental Biology
- Pharmacology
Background:
- Thyrotropin releasing hormone (TRH) plays a role in regulating behavior.
- The developing rat brain exhibits unique neurochemical sensitivities.
Purpose of the Study:
- To investigate the behavioral effects of TRH in developing rats.
- To examine the influence of neonatal 6-OHDOPA administration on TRH-induced behaviors.
Main Methods:
- Rats of various ages (7, 14, 20, 30 days, and adult) were injected with TRH.
- Neonatal rats received 6-OHDOPA pretreatment.
- Pharmacological antagonists (alpha-flupenthixol, phenoxybenzamine) were used to probe receptor involvement.
Main Results:
- TRH induced locomotor stimulation and behavioral arousal across development.
- Neonatal 6-OHDOPA significantly potentiated TRH effects in 7-day-old rats.
- This potentiation was blocked by dopamine and alpha-adrenergic antagonists.
Conclusions:
- Central dopamine neurons are implicated in TRH-mediated behavioral arousal in infant rats.
- Early-life neurochemical alterations can modify neurohormonal responses.
Abstract:
The behavioral effect of thyrotropin releasing hormone (TRH) was investigated in the developing rat pretreated with 6-OHDOPA at birth. An IP injection of TRH (20 mg/kg) increased walking with sniffing, rearing, body shaking, grooming, chewing and licking in the 7-, 14-, 20- and 30-day-old as well as in the adult rat. TRH-induced locomotor stimulation began a few minutes after the injection and lasted for approximately 60 min. But on Day 7, TRH produced locomotor stimulation betwen 1.5 hr and 3.5 hr after the injection. Neonatal treatment with 6-OHDOPA markedly potentiated TRH-induced locomotor stimulation and behavioral arousal in the 7-day-old rat but not in the 14-day-old and adult rat. The marked potentiation of TRH-induced locomotor stimulation by 6-OHDOPA in the 7-day-old rat was reduced by alpha-flupenthixol (pA2=5.9) and phenoxybenzamine (pA2=4.4). These results suggest that central dopamine neurons are involved in TRH-induced behavioral arousal in the infant rat.