Differential effects of colchicine on the induction of nitric oxide synthase in neurons containing progesterone receptors of the guinea pig hypothalamus

Using nicotinamide-adenine-dinucleotide-phosphate-diaphorase (NADPHd) histo chemistry, we analyzed the effects of an intracerebroventricular injection of colchicine on the activity of neuronal nitric oxide synthase in the hypo thalamic nuclei of intact and ovariectomized estradiol-primed guinea pigs, We also examined the effects of colchicine on the immunocytochemical coloca lization of nitric oxide synthase with the progesterone receptor in the ven trolateral nucleus, a key region in the control of sexual behavior. Treatme nt with colchicine resulted in a significant increase in the number of NADP Hd-positive neurons in the ventrolateral nucleus in intact as well as in ov ariectomized estradiol-primed animals, whereas in the other hypothalamic re gions analyzed (preoptic area, paraventricular nucleus and posterior arcuat e nucleus), the enzymatic activity remained unchanged. Quantitative analysi s showed a significantly greater number of NADPHd-positive cells in the med ial and the posterior aspects of the ventrolateral nucleus of colchicine-tr eated guinea pigs compared to the control group. In the caudal subdivision of this nucleus, colchicine induced nitric oxide synthase in the target cel ls for progesterone. These results suggest that neuronal nitric oxide synth ase activity in the hypothalamus is affected by colchicine in a region-spec ific manner and especially in the ventrolateral nucleus, which is involved in progesterone-facilitated lordosis, (C) 2000 Elsevier Science Inc.