Electrical stimulation of the paraventricular nucleus attenuates pyrogen fever in the rabbit

Abstract

Arginine vasopressin (AVP) perfused within the ventral septal area (VSA) suppresses fever normally evoked by pyrogenic substances, including Salmonella abortus equi (SAE). Neurons containing AVP and located within the paraventricular nucleus (PVN) or the nearby bed nucleus of the stria terminalis (BnST) are believed to have projections to this septal region. A series of experiments was undertaken to determine whether electrical stimulation of these areas, which might be expected to cause the release of AVP within the VSA, would affect similarly the pathogenesis of fever. A stainless steel cannula was implanted surgically in each of 22 male New Zealand White rabbits and a monopolar electrode was lowered through this guide cannula to the PVN or BnST areas. Electrical stimulation (20 Hz, 10 s on, 10 s off, 2.6–3.2 V) was initiated 30 min prior to and was continued until 90 min after the intravenous (i.v.) adminisstration of 0.1–1.0 μg of SAE (1.0 ml carrier vehicle ). While afebrile body temperature remained unchanged, electrical stimulation of sites located in the rostral extension of the PVN effectively attenuated the pyrogen-induced fever. Stimulation of sites outside these areas did not affect either the absolute magnitude or the duration of the fever. Although the reduction in fever was most pronounced during the period of electrical stimulation, in some cases the fever remained suppressed beyond the application of the current. These experiments provide the first evidence that electrical stimulation of paraventricular areas with AVP-containing cell bodies is effective in suppressing a fever evoked by systemic administration of a pyrogen. Although untested, it is possible that a stimulus-induced release of AVP within the VSA is responsible for the attenuation of the fever.