Changes in the Expression of с-fos and NADPH-Diaphorase Activity in Rat Hippocampal Structures Related to Food Deprivation and Realization of Operant Food-Procuring Movements

The expression of early c-fos gene (marker of neuronal activation) and NADPH-diaphorase reactivity (NADPH-dr) was studied in various hypothalamic structures of rats in the norm, in the state of starvation, and after realization of long-lasting (repeated 4 to 12 times per minute for 30 min) motivated stereotyped food-procuring forelimb movements. In rats in the starving state, as compared with the control, the densities (number of units within a 200 × 200 μm² test area of a 40-μm-thick slice) of Fos-immunoreactive (Fos-ir) neurons in the parvicellular part of the paraventricular nucleus (Ра), supraoptic (SO), and medial preoptic (МРО) nuclei, anterior hypothalamic region (АН), and lateral hypothalamic nucleus (LH) were significantly greater (Р < 0.05) than in the control. In the dorsomedial (DMD) and ventromedial (VMHD) hypothalamic nuclei, this index did not differ from control values. After the performance of intense unilateral operant movements, higher densities of labeled neurons (as compared with that in control and starving animals) were observed in the PаAP, SO, МРО, and DMD, while smaller densities were observed in the LH and VMH. NADPH-dr neurons (i.e., NO synthase-containing cells) were observed in many hypothalamic nuclei; the maximum density of such NO-generating neurons was found in the Pa, SO, MPO, and DMD. The overwhelming majority of Fos-ir and NADPH-dr neurons in neurons was observed after realization of stereotyped food-procuring movements in the Ра and SO. This specificity of changes in the number of Fos-irand NADPH-dr neurons in the hypothalamic nuclei reflects, perhaps, the involvement of these structures in the control of autonomic functions in the course of realization of operant reflexes and adaptation of the function of the cardiovascular system to the corresponding intense physical and emotional loading.