Sexually dimorphic MK801-induced c-fos in the rat hypothalamic paraventricular nucleus

MK801 induces Fos-like immunoreactivity (FLI) in the paraventricular nucleus (PVN) in a sex, age, hormone and dosage dependent manner. MK801 (1.0 mg/kg) elicited greater behavioural disruption, but less FLI in the PVN of cycling and lactating female rats, compared to like-treated males. Results from gonadectomized rats with or without acute steroid replacement resembled those seen in intact rats but sex differences were extinguished. At a lower dose (0.1 mg/kg), behavioural effects were diminished but females exhibited more behavioural disruption. At this dose however, more FLI was seen in the PVN of females compared to males, but only male-lactating female differences were significant. Taken together, the data suggest that the action of MK801 on the PVN is influenced by gonadal steroids.