[5-HT3 receptors in amygdala mediate neuroimmunomodulation in rats]

The present study was to explore the possible immunomodulatory role of 5-HT3 receptors in the amygdala in rats. Concanovalin A (Con A)- and lipopolysaccharide (LPS)-stimulated splenocyte proliferation response (SPR), production of IL-2, activity of natural killer (NK) cells and serum cortisol were measured by 3H-TdR incorporating method, MTT method and RIA, respectively. The Con A- and LPS-stimulated SPR was enhanced in a dose-dependent manner by 5-HT3 receptor antagonist granisetron (GNT) (0.1-0.4 mg/kg, i.p.). SPR was also enhanced by intracerebroventricular (icv) administration of 1-phenylbiguanide (PBG, 10 micrograms/d). Con A-stimulated SPR and production of IL-2 were increased either by bilateral or by unilateral central amygdala (CeA) microinfusion of PBG (0.5 microgram/side), but LPS-induced SPR and NK cell activity were not affected. On the contrary, the LPS-induced SPR was increased by either bilateral or unilateral basomedial amygdala (BmA) microinfusion of PBG (0.5 microgram/side). The plasma cortisol level was significantly raised by CeA or BmA PBG microinfusion, but the effect induced by PBG intra-CeA was greater than that induced by PBG intra-BmA (P < 0.01). The effects of icv PBG and intra-amygdala infusion were antagonized by granisetron. Asymmetrical modulation of immune reactivity by 5-HT3 receptors in CeA or BmA was not observed in these experiments. It is suggested that 5-HT3 receptors within the amygdala may modulate rat mitogen-stimulated SPR in different manners.