| Abstract: | Evoked potential (EPs) and responses of the medial (MPO) and lateral (LPO) preoptic region (RPO) and adjacent structures of the hypothalamus to stimulation of the prefrontal (area 8) and cingulate (area 24) cortex, piriform lobe (periamygdaloid cortex), and hippocampus (area CA3) were investigated in acute experiments on cats under ketamine anesthesia. The most pronounced EPs were observed in the RPO after stimulating the piriform and cingulate cortex. A close relation was found between neuronal responses and EP components. The majority of neurons responding to stimulation of various cortical structures were localized in the LPO, where primarily excitatory responses dominate. The MPO contained somewhat fewer neurons responding to cortical stimulation, and the dominant response here was primarily inhibitory. The ratio of inhibitory and excitatory responses in the LPO was 0.6:1 and in the MPO 5.8:1. Primarily in-inhibitory responses dominated also in the LPO zone adjacent to the bed nucleus stria terminalis (BST) and primarily excitatory in the region surrounding the supraoptic nucleus (SO) (respective ratios 4.9:1 and 0.7:1). The RPO is a broad convergence zone, where 3/4 of the neurons responded to stimuli of two and more cortical regions.A. M. Gorky Medical Institute, Ukrainian Minstry of Health, Donetsk. Translated from Neirofiziologiya, Vol. 23, No. 6, pp. 709–719, November–December, 1991. |
