Inhibitory effects of thyrotropin-releasing hormone on neuronal activity in the nucleus accumbens.
The effects of thyrotropin-releasing hormone (TRH) were examined on neuronal activity in the nucleus accumbens, receiving an input from the parafascicular nucleus of the thalamus or the hippocampus, in chloral hydrate-anesthetized rats, using a microiontophoretic technique. The spikes produced by stimulation of the parafascicular nucleus were predominantly and dose-dependently inhibited during iontophoretic application of TRH. When the effects of TRH and dopamine were tested on the same neurons of the nucleus accumbens, inhibition of the generation of spikes by both drugs was observed in most neurons. In contrast, spikes elicited by stimulation of the hippocampus in most neurons of the nucleus accumbens were not affected by TRH or dopamine. Both TRH- and dopamine-induced inhibition of the spikes induced by stimulation of the parafascicular nucleus was antagonized by simultaneous application of haloperidol. In animals treated with reserpine, inhibition of the generation of spikes upon stimulation of the parafascicular nucleus did not occur in any neurons in the nucleus accumbens during application of TRH, whereas the dopamine-induced inhibition was still observed. These results suggest that inhibitory effects of TRH on the neurons of the nucleus accumbens receiving an input from the parafascicular nucleus are mediated by dopamine released from the dopaminergic nerve terminals located in the nucleus accumbens.
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D004298:Dopamine / Q000494:pharmacology; D004558:Electric Stimulation; D004594:Electrophysiology; D006220:Haloperidol / Q000494:pharmacology; D006624:Hippocampus / Q000502:physiology; D008297:Male; D009433:Neural Inhibition / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009714:Nucleus Accumbens / Q000166:cytology / Q000187:drug effects*; D051381:Rats; D012110:Reserpine / Q000494:pharmacology; D012686:Septal Nuclei / Q000187:drug effects*; D013787:Thalamic Nuclei / Q000502:physiology; D013973:Thyrotropin-Releasing Hormone / Q000494:pharmacology*
D013973:Thyrotropin-Releasing Hormone; D012110:Reserpine; D006220:Haloperidol; D004298:Dopamine