CHRONIC LATERAL VENTRICLE INFUSION OF A PINEAL GLAND-DERIVED DECAPEPTIDE ALTERS PULSATILE SECRETION OF LH IN RATS

The object of this investigation was to determine whether chronic late ral ventricle infusion of a pineal gland-derived antigonadotropic deca peptide (AGD) would affect pulsatile luteinizing hormone (LH) release in conscious, unrestrained male rats. Adult male Harlan SD rats were b ilaterally orchiectomized and maintained under conditions of controlle d photoperiods and temperature. After three (Experiment one) or four ( Experiment two) weeks each was fitted stereotaxically with a stainless steel cannula for infusion into the right lateral ventricle. Each can nula was attached to a subcutaneous osmotic minipump filled either wit h artificial cerebrospinal fluid (CSF) or AGD in CSF (0.5 mu g/mu l). CSF (1.0 mu l/hr) or the AGD (0.5 mu g/mu l/hr) was infused over a per iod of four days. Blood samples for determination of LK by radioimmuno assay were obtained at five minute intervals from a Tygon microbore ca nnula inserted via a femoral artery into the abdominal aorta. LH pulse s were defined and identified with a computerized deconvolution algori thm designed to determine spontaneous LH secretory events. Although me an LH levels were not significantly reduced, LH secretory pulse freque ncy and nadirs were significantly decreased by AGD infusion (p<0.01). Additionally, LH secretory pulse amplitude and the LH secretory respon se to LHRH administration were significantly increased (p<0.01) by AGD treatment. These results confirm initial reports of depressive effect s of the AGD on LH secretion and support its hypothesized central site of action.