Central respiratory stimulant effect by thyrotropin in releasing hormone in the rat

Anaesthetized male rats were injected intracerebroventricularly with the tripeptide, thyrotropin releasing hormone (TRH). Respiratory frequency (f), tidal volume (VT) and minute volume (VE) were measured in a closed whole body plethysmograph by a low pressure transducer connected to a Grass polygraph. TRH induced an approximately 50% increase in f, while VT was not altered. VE increased in the same proportion as f. Our results indicate that TRH neurons or TRH-sensitive receptors may be involved in the regulation of central respiratory activity.