Reinforcing properties of the neuropeptide substance P in Carassius auratus: evidence of dopaminergic system involvement.
The aim of the present study was to investigate whether neuropeptide substance P (SP) has reinforcing effects in Carassius auratus and whether this effect could be related to dopaminergic neurotransmission. For this purpose fishes were put in a three-compartment box in which one compartment gave access to two others that did not directly link. The time spent in each compartment was registered for 10 min to determine a possible preferred compartment. Twenty-four hours later, the fish were given one of the following intraperitoneal treatments: a) Group VEH, injected with the vehicle of substance P; b) Group SP25, injected with SP, 25 micrograms/kg body wt.; c) Group SP50, injected with SP, 50 micrograms/kg; or d) Group HALO, injected with haloperidol (2 mg/kg) 30 min before an injection of SP (50 micrograms/kg). Immediately after the treatment the fish were kept for 30 min in the compartment preferred least the day before. On the next day the fish were retested for 10 min to verify the time spent in each compartment. The results indicate that SP at the dose of 50 micrograms/kg enhanced the time spent on the paired compartment, and that the pretreatment with haloperidol abolished this enhancement. It is suggested that SP has reinforcing effects in C. auratus that may be mediated by the dopaminergic system.
Mattioli
R
R
Laboratory of Neuroscience, DEFITO, Universidade Federal de São Carlos, Brazil.
Aguilar
C
C
Vasconcelos
L
L
D000818:Animals; D003216:Conditioning, Operant / Q000187:drug effects; D004298:Dopamine / Q000502:physiology*; D006054:Goldfish / Q000502:physiology*; D006220:Haloperidol / Q000494:pharmacology; D012054:Reinforcement, Psychology; D013373:Substance P / Q000037:antagonists & inhibitors / Q000494:pharmacology*
D013373:Substance P; D006220:Haloperidol; D004298:Dopamine