Cholinergic input to the supraoptic nucleus increases Fos expression and body temperature in rats

Abstract

To examine the role played by cholinergic input and processes in the supraoptic nucleus (SON) in the control of body temperature and water intake in rats, we used microdialysis to stimulate and analyze SON without disturbing the behavior of unanesthetized rats. After microdialysis, we also investigated immunoreactivity for c-Fos protein in the brain as an index of neuronal activation. Stimulation with neostigmine, an acetylcholine esterase inhibitor, through the microdialysis probe increased the extracellular concentration of acetylcholine in the SON. This cholinergic stimulation dose-dependently increased body temperature but did not significantly change the water intake. The stimulation markedly increased c-Fos-like immunoreactivity (Fos-IR) in the SON and certain hypothalamic areas, including the paraventricular nucleus (PVN) and median preoptic nucleus (MnPO). Fos-IR was also evident in certain regions of the pons and brainstem, including the locus ceruleus (LC), area postrema (AP), and nucleus of the solitary tract (NTS). Addition of atropine, a muscarinic receptor antagonist, to the dialysis medium containing neostigmine attenuated the increase of Fos-IR and suppressed the neostigmine-induced responses in body temperature. These results suggest that cholinergic input and activation of the muscarinic cholinoceptive neurons in the SON contribute to the regulation of body temperature. Activation of noradrenergic pathways in the brainstem including LC and NTS may be involved in the thermoregulation mechanism.

Sex Differences in Fos Protein Expression in the Neonatal Rat Brain

“…These neurotransmitters also regulate Fos expression in the developing and adult brain. That is, dopamine induces Fos expression in fetuses (57, 58) and neonates (17), and norepinephrine (59) and acetylcholine (60, 61) both induce Fos expression in adults, indicating that sex differences in these neurotransmitter systems may contribute to sex differences in Fos expression. Another possibility is that the sex differences in Fos expression may partially result from a sex difference in response to a particular transmitter.…”

Effects of acute heat exposure on prosencephalic c-Fos expression in normohydrated, water-deprived and salt-loaded rats

“…Several findings indicate that the SON participates in thermoregulatory events. Indeed, it has recently been suggested that thermal information from the preoptic area sends excitatory signals to the SON (Yoshida et al, 2002), that cholinergic inputs to the supraoptic nucleus increase Fos expression and body temperature in rats (Takahashi et al, 2001a), and that neurons located in the SON increase nonshivering thermogenesis in brown adipose tissue by activating sympathetic pathways (Takahashi et al, 2001b). Therefore, it seems rational to suggest that this type of heat-producing circuitry is inactive in animals undergoing an increase in body temperature due to exposure to a warm environment.…”