This study compared the ability of CRF and UCN1 to induce a thermoregulatory response when centrally injected into rats. The effects of
antipyretic drugs and
CRF receptor antagonists (CRF₁ and CRF₂) on the temperature (T) changes induced by these
peptides were also investigated. Rectal (rT) and tail skin (T(sk)) temperatures were measured with a thermistor probe while body (bT) temperature was measured with a battery-operated biotelemetry transmitter in male Wistar rats (200 g) every 30 min over a period of 6h, after intracerebroventricular (i.c.v.) injection of 1 nmol of either CRF or UCN1. Rats were pre-treated with
indomethacin (2 mg kg⁻¹, i.p.) or
celecoxib (5 mg kg⁻¹, p.o.),
dexamethasone (0.5 mg kg⁻¹, s.c.),
astressin (a CRF₁/CRF₂ antagonist, 7 nmol, i.c.v.) or
antalarmin (a CRF₁ antagonist, 20 mg kg⁻¹, i.p.). The increase in body temperature induced by CRF was accompanied by a reduction in T(sk) while the response induced by UCN1 was accompanied by an elevation in T(sk).
Indomethacin or
celecoxib did not change the increases in rT caused by either CRF or UCN1. Although
dexamethasone attenuated the increase in rectal temperature in response to CRF,
dexamethasone did not modify the response induced by UCN1.
Astressin blocked the UCN1-induced
hyperthermia and reduced CRF-induced
fever.
Antalarmin did not modify the
hyperthermia in response to UCN1, but reduced the
fever evoked by CRF. This study demonstrated that CRF by acting on the CRF₁ receptor induces a
prostaglandin-independent
fever which seems to depend, at least in part, on the synthesis of other mediators while UCN1 acts on the CRF₂ receptor, promoting a hyperthermic response which seems to be independent on synthesis/release of any mediator.