Effects of pretreatment with luteinizing hormone releasing hormone (LHRH) on behaviors induced by apomorphine in rats.
The influence of LHRH on the behavioral effects induced by apomorphine (APO) was studied in male rats. Several doses of apomorphine (31.25, 62.5, 125, 250 and 500 micrograms/kg) were administered subcutaneously (SC) after LHRH 100 micrograms/kg or solvent. Low doses of apomorphine induced hypomotility and impaired acquisition of a conditioned avoidance response (CAR). High doses produced hypermotility, stereotyped sniffing and a short lasting increase, followed by a decrease in the acquisition of CARs. Pretreatment with LHRH potentiated the hypomotility induced by low doses of apomorphine (62.5 and 125 micrograms/kg) and the hypermotility, stereotyped sniffing and the enhancement in acquisition of CARs produced by higher doses of apomorphine (250 and 500 micrograms/kg). These findings suggest that LHRH could indirectly regulate dopamine activity through an increase in sensitivity of dopamine receptors (pre- and postsynaptic), which mediate the behavioral effects of APO. It is postulated that this hypersensitivity of DA receptors could be the consequence of an inhibition of presynaptic dopaminergic transmission, induced by LHRH.
Mora
S
S
Departamento Preclinicas, Facultad de Medicina, Universidad de Chile, Santiago.
Diaz-Veliz
G
G
D000818:Animals; D001058:Apomorphine / Q000494:pharmacology*; D001522:Behavior, Animal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D007987:Gonadotropin-Releasing Hormone / Q000494:pharmacology*; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D011954:Receptors, Dopamine / Q000502:physiology; D013997:Time Factors
D011954:Receptors, Dopamine; D007987:Gonadotropin-Releasing Hormone; D001058:Apomorphine