Effect of some benzodiazepines on the secretion of thyrotropic hormone and prolactin under conditions of experimental stress.

The effects of diazepam and medazepam, administered repeatedly orally, on the secretion of thyrotropic hormone and prolactin in male sexually matured albino rats were investigated under conditions of acute cold and immobilization stress. The agents were administered for 30 days in doses of 1 and 5 mg/kg for diazepam, and 1 and 10 mg/kg for medazepam. Sixty minutes after the last injection, the animals were placed under conditions of low temperature--+4 degrees C (cold stress) and of immobilization (immobilization stress) for 60 min. The content of thyrotropic hormone (TTH) and of prolactin in the serum of the control and experimental animals was determined using radioimmunological methods. Diazepam and medazepam were found to inhibit prolactin secretion under stress, affecting TTH secretion only in high doses: 5 mg/kg diazepam and 10 mg/kg medazepam. The TTH content was reduced under conditions of cold stress. The role of GABA and of the benzodiazepine receptors in the central nervous system in the regulation of the secretion of prolactin and TTH under states of stress is discussed.