Increased Locomotor Activity In Rats Research Articles

Does environmental enrichment increase locomotor activity in rats? Evidence from an implanted sensor device

Does environmental enrichment increase locomotor activity in rats? Evidence from an implanted sensor device

The role of catecholamines in desmopressin induced locomotor stimulation.

Central and peripheral administration of DDAVP increase locomotor activity in rats in doses that alter brain dopamine neurochemistry. In order to delineate the role of catecholamines in this behavioural effect of DDAVP, the effects of different catecholamine manipulating agents on DDAVP-induced locomotor stimulation were studied in rats. The catecholamine depleting agent reserpine (5 mg/kg), administered alone or together with the catecholamine synthesis inhibitor alpha-methyltyrosine (250 mg/kg), completely prevented the locomotor stimulatory effect of DDAVP. The dopamine D1 receptor antagonist Sch-23390 (0.01 and 0.03 mg/kg) significantly antagonized the DDAVP-induced locomotor stimulation when administered in the higher dose, that also produced a significant reduction of locomotor activity per se, whereas the dopamine D2 receptor antagonist raclopride (0.08 and 0.16 mg/kg) had no significant effect. The two dopamine blockers administered together produced a significant, dose-dependent reduction of DDAVP-induced locomotor stimulation, while controls were not significantly affected. Also the alpha-adrenoceptor antagonist phenoxybenzamine decreased the DDAVP-induced locomotor stimulation in a dose (20 mg/kg) that did not influence locomotor activity in controls, and, finally, administration of Sch-23390, raclopride and phenoxybenzamine antagonised the DDAVP-induced effect in a dose combination that failed to influence locomotor activity per se. In vivo microdialysis experiments in awake, freely moving rats indicated that DDAVP increases dopamine overflow in the nucleus accumbens, a brain area of importance for initiation of locomotor activity, by approximately 25%, as compared to baseline levels. Taken together, these results indicate that the central stimulatory action of DDAVP involves granula-mediated dopamine release and subsequent activation of dopamine D1 and D2 receptors, and that alpha-adrenoceptors possibly also are involved.

Substance P injections into the ventral tegmentum affect unit activity in mesolimbic terminal regions

Microinjections of substance P (SP) into the ventral tegmental area (VTA) increase locomotor activity in rats, and this effect is thought to be produced by activation of the mesolimbic dopamine system. In the present study, firing rates of neurons in areas receiving projections from the mesolimbic dopamine system were recorded during injections of SP (3 μg in 0.5 μl saline) into the VTA of rats anesthetized with chloral hydrate. Significant changes in firing rates were observed in 84% of the units recorded in nucleus accumbens and olfactory tubercle. There were mostly decreases in nucleus accumbens (NAC, 21 of 25 units affected by SP) and mostly increases in olfactory tubercle (OT, 13 of 18 units affected by SP). In contrast, neither saline injections into VTA nor SP injections 2 mm dorsal to VTA had any effect on NAC or OT neurons. Haloperidol (0.5 mg/kg IV) blocked the effects of SP, suggesting that effects were mediated, at least in part, by the mesolimbic dopamine system. Results indicated that activation of dopaminergic neurons by SP injections into VTA can produce changes in the activity of neurons in NAC and OT, areas which receive mesolimbic dopaminergic projections.