Effects of dopaminergic and cholinergic drugs. naloxone and l-prolyl-leucyl-glycinamide on LSD-induced catalepsy

Pro-Leu-glycinamide and its peptidomimetic, PAOPA, attenuate haloperidol induced vacuous chewing movements in rat: A model of human tardive dyskinesia

In the present experimental paradigm, we examine the effect of L-prolyl-L-leucyl-glycinamide (PLG) co-administration with haloperidol on vacuous chewing movements (VCM) in rats-a model of tardive dyskinesia (TD) in humans. We examined the dose dependent induction of VCM through both injected and orally administered PLG (MIF-1). Our results show significant levels of VCM attenuation (P<0.05) in rats treated with 10mg/kg of PLG. Doses of 1 and 100mg/kg were ineffective. Reductions were present in both orally treated and injected rats. We also examined the therapeutic effect of a peptidomimetic of PLG-PAOPA. PAOPA was able to produce similar behavioral effects to PLG at a dose, which was 100-fold lower than the effective dose of PLG. These results suggest that PLG may play a role in D2 receptor expression and function, as well as providing a therapy for neuroleptic induced TD.

Differences in the central actions of arachidonic acid and prostaglandin F2 alpha between spontaneously hypertensive and normotensive rats

Prostaglandin F2 alpha (PGF2 alpha) is one of the most common metabolites of arachidonic acid (AA) in rat brain. When administered intracerebroventricularly (i.c.v.) to rats, both AA and PGF2 alpha exert dose-related hypertensive, tachycardic and hyperthermic effects. Metabolic alterations in the endogenous formation of some prostaglandins in the brain-stem of spontaneously hypertensive rats (SHR) have been reported. Therefore the central effects of AA and PGF2 alpha on blood pressure, heart rate and body temperature were studied by in SHR and normotensive Wistar rats (NR) under urethane-anaesthesia. The hypertensive effect of AA i.c.v. (0.01-100 micrograms/rat) was larger in magnitude of SHR than in NR, but there was no significant difference in the AA-induced changes of heart rate and body temperature between the groups. Pretreatment of NR with sodium meclofenamate (1 mg/rat i.c.v.) antagonised the central effects of AA indicating that these effects are not due to AA itself but it its conversion to prostaglandins. Unlike the effects of AA, the central hypertensive, tachycardic and hyperthermic responses to PGF2 alpha (0.5-50 micrograms/rat i.c.v.) were significantly attenuated in SHR. The present results obtained with AA are compatible with the previous assumption that the synthesis of prostaglandins in the brain of SHR might differ from that in NR. The results also demonstrate that the central effect of PGF2 alpha are reduced in SHR.