Integration of thermal and osmotic afferent signals in the preoptic/anterior hypothalamic neurons

Modulation of spiking of neurons of the cat anterior hypothalamus induced by experimental shifts in the osmolarity of the blood plasma

“…Intracarotid infusions of the solutions differing in their osmolarity from the blood plasma induce shifts in the water/salt balance in the bed of the a. carotis and in the cerebral vessels; these shifts are percepted by the corresponding receptor structures of the nervous system [1,4,6]. Osmoreceptors localized within the periphery and immediately on the membrane of central neurons respond to these fluctuations.…”

“…Activating responses of these neurons prevail, as compared with inhibitory reactions; this fact probably shows that shifts of the water/salt balance in both directions (toward both hyper-and hypoosmolarity) result in the formation of a rather strong nidus of activation in the anterior hypothalamus; this serves as a basis for the formation of the corresponding motivations and for initiation of adequate behavioral acts in future [2,4,9,10,13]. At the same time, constellations of the neurons, whose activity was significantly enhanced or suppressed under conditions of hyper-vs hypoosmolarity, were found to be very similar.…”

“…At present, there is an enormous store of data relating to the role of the hypothalamus in the central control of visceral functions and maintenance of homeostasis of the internal medium of the organism [1][2][3][4][5][6]. The active involvement of the hypothalamic neuronal systems in the control of the osmotic state is beyond doubt; at the same time, it should be taken into consideration that the maintenance of a few homeostasis constants provided by the hypothalamus is necessarily realized by interaction of the above complex of structures with other central mechanisms.…”

“…Changes in the corresponding physiological conditions, which result in shifts in the osmotic pressure and ion composition of the blood plasma (and other liquid media connected with the latter), are responsible for the reversible modifications of the functional relations among cells of different types and functional properties of the neurons per se. These modifications influence directly the parameters of the impulse activity (IA) of these neurons and are manifested in the corresponding modulations of this activity [3,4,[6][7][8]. These effects should, probably, be considered the most important component of the process of formation of central commands providing stability of the main parameters of homeostasis [7].…”

“…Over recent years, cortico-hypothalamic connections, as well as hypothalamic neurons involved in the regulation of water/salt homeostasis, were the objects of our studies [1][2][3][4]9]. In this communication, we describe data on the identification and classification of modifications of the IA generated by neurons of the anterior hypothalamus (in particular, by RPO cells) induced by experimental variation of the most important homeostatic constant, namely, the osmotic pressure of the blood plasma.…”