INVOLVEMENT OF CENTRAL NEUROTENSIN IN THERMOREGULATORY AND NEUROIMMUNE FUNCTION IN PREGNANT RATS EXPOSED TO HEAT

To examine a functional relationship among pregnancy and central neuro tensin and thermoregulatory and neuroimmune systems during heat stress , we monitored colonic temperature in six virgin female rats and six p regnant rats (9 to 11 days gestation) exposed to a microwave source. W e also assayed splenic natural killer cell activity (NKCA), blood cort icosterone (CS), and ACTH as indicators of the hypothalamic-pituitary- adrenal axis, beta-endorphin (beta-EP), and neurotensin (NT) in discre te brain regions. Additionally, we clarified the effects of intracereb roventricular (icv) administration of NT antiserum on these same respo nses in pregnant rats exposed to heat stress. Repeated-measures analys is of variance showed significant main effects of heat and pregnancy a nd a significant interactive effect on colonic temperature. Significan t elevation in blood CS, ACTH, beta-EP, and NT in the hypothalamus and significant reductions in splenic NKCA and NT in the nucleus accumben s were produced by heat. In the experiment examining the effect of icv administration of NT antiserum, significant main effects of heat and administration and a significant interactive effect on colonic tempera ture were observed. Icv administration of NT antiserum increased splen ic NKCA and decreased blood beta-EP. These results show that pregnancy enhances thermal homeostasis, suggesting central thermoregulatory mec hanisms through NT in nucleus accumbens and hypothalamus in which plac ental or pituitary beta-EP may be involved. NT and beta-EP seem to pla y central roles simultaneously in heat-induced immunosuppression durin g pregnancy. Clarification for the effects of NT antiserum on beta-EP in virgin rats or manipulation of agents related to opioid system shou ld be the focus of future work. (C) 1997 Academic Press.