Central noradrenergic system modulates plasma interleukin-6 production by peripheral interleukin-1.

The role of the central noradrenergic system in systemic interleukin-6 (IL-6) production induced by intravenously administered recombinant human interleukin-1 beta (IL-1 beta) was examined in rats. Pretreatment of rats intracerebroventricularly with 6-hydroxydopamine (6-OHDA, 100 or 200 micrograms/rat) significantly attenuated the increase in plasma IL-6 levels caused by IL-1 beta (2 micrograms/kg i.v.). A modest inhibition of the IL-1 beta-induced plasma IL-6 production was observed following pretreatment with prazosin (20 micrograms/rat i.c.v.) but not after administration of idazoxan or propranolol. There were no significant increases in the IL-6 content in the hypothalamus, medulla oblongata, and cortex of the brain after intravenous IL-1 beta. Adrenalectomy produced an augmented plasma IL-6 response to intravenous IL-1 beta, whereas chemical sympathectomy with intraperitoneal injection of 6-OHDA (50 or 100 mg/kg) decreased the IL-1 beta-induced plasma IL-6 levels. Nor-epinephrine (NE), in the dose range 10(-6)-10(-4) M, significantly increased the IL-6 levels in the rat spleen lymphocyte culture media. At doses of 10(-9)-10(-7) M, NE enhanced the effect of IL-1 beta on the IL-6 release by spleen lymphocytes in a dose-dependent manner. These findings suggest that the plasma IL-6 response to intravenous IL-1 beta is partially mediated through the activation of the central noradrenergic system and a consequent increase in the sympathetic outflow to the peripheral tissues and that the NE released from the sympathetic terminals may function as a mediator and/or modulator to facilitate the synthesis/release of IL-6 in the sympathetic nerve-innervated organs.

Feeding suppression elicited by electrical and chemical stimulations of monkey hypothalamus.

The effects of electrical (ES) and chemical stimulations of the hypothalamus were investigated in monkeys during bar-press feeding. ES elicited both prolonged and nonprolonged types of suppression of bar-press feeding in hungry animals. Prolonged type suppression persisted for greater than 1 min beyond one or more post-ES trials and was found after ES of the dorsomedial hypothalamus (DMH), the ventromedial hypothalamus (VMH), and the ventromedial part of the lateral hypothalamic area (LHA). Non-prolonged type suppression was observed only during ES at some sites of both in hypothalamic and extrahypothalamic areas. A microinjection of glutamate into the VMH and the DMH, but not into the LHA, was able to reproduce the ES-induced prolonged type suppression. In contrast, the ES of the LHA, but not the VMH and DMH, in a satiated state provoked feeding. The results, together with the previous findings, suggest that the neuronal inhibitory mechanism of feeding exists in the VMH and DMH, while both the neuronal facilitatory and axonal inhibitory mechanisms in the LHA are involved in the feeding regulation, and these mechanisms of the LHA are affected by the hunger/satiety state.

Electrical stimulation of male monkey's midbrain elicits components of sexual behavior.

We electrically stimulated the midbrain of male rhesus monkeys seated in a restraint chair facing the female partners and examined whether sexual behavior could be induced. When the midbrain was stimulated (0.2 ms, 50-500 microA and 50 Hz for 2.5 s), the male monkey touched and held the waist of his partner (latency; 0.9 +/- 0.4 s, mean +/- SD, n = 225), and then mounted her when she responded with presenting her hip toward him. However, this mounting, unlike when the hypothalamus was stimulated, did not lead to thrusting or ejaculation even if the stimulation continued. The sites in the midbrain where the stimulation elicited touching and mounting were the ventral tegmental area, the substantia nigra, the nucleus reticularis mesencephali and the nucleus reticularis pontis oralis et caudalis. Touching and mounting were not elicited when the partner was put away from the male or replaced by submissive male monkeys or humans. The findings suggest that the stimulation-evoked touching and mounting are components of copulatory behavior and that the midbrain structures may be involved in the sexual behavior of male monkeys.