ABSTRACT
OBJECTIVE: Post weanling isolation-reared (IR) rats are featured with depressive phenotype, yet its mechanism is not clearly defined particularly in terms of the involvement of central 5-HT1A receptors. The present study aims to examine the effects of 5HT1A activation on forced swim test (FST) in IR rats following 5-HT depletion. METHODS: Social control (SOC) and IR rats received an intracerebraoventricular (ICV) injection of 5-HT depletion agent, 5,7-DHT. 14 days after the surgery, rats were assessed their performance in FST with or without the challenge with a 5-HT1A agonist, 8-OH-DPAT. Rats were then sacrificed for analyzing their 5-HT tissue levels and the expressions of their 5-HA1A receptors in prefrontal cortex (PFC), hippocampus (HPX), and amygdala (AMY). RESULTS: 5,7-DHT decreased the tissue concentration of 5-HT in both IR and SOC rats. IR rats were more immobile and less sensitive to the lesion-induced immobility, however this effect was reversed by acute challenge of 8-OH-DPAT. 5,7-DHT lesion increased the expression of PFC 5-HT1A receptors. CONCLUSION: The integrity of central 5-HT system is developmentally crucial for the 5-HT1A-relevant depression profile in rats of social isolation.
Subject(s)
Animals , Rats , 8-Hydroxy-2-(di-n-propylamino)tetralin , Amygdala , Depression , Hippocampus , Phenotype , Prefrontal Cortex , Receptor, Serotonin, 5-HT1A , Serotonin 5-HT1 Receptor Agonists , Serotonin , Social Control, Formal , Social IsolationABSTRACT
OBJECTIVE: Central 5-HT1A receptor is involved in the modulation of sensorimotor gating function. However, its precise role is not clearly defined in developmentally social deprived (isolation rearing, IR) rats featured with impaired sensorimotor gating ability. We therefore aimed to examine the effects of 5HT1A activation on acoustic startle response (ASR) and prepulse inhibition (PPI) in IR rats in a condition of compromised presynaptic 5-HT functions. METHODS: Social control (SOC) and IR rats received an intracerebraoventricular (ICV) injection of 5-HT depletor, 5,7-DHT. Seven days later rats entered a protocol of 8-OH-DPAT, a 5-HT1A agonist, in which locomotor activity, ASR and PPI and their tissue levels of 5-HT were measured. RESULTS: Our results found that both IR and 5,7-DHT decreased the tissue concentration of 5-HT. IR-induced hyperactivity and gating impairment were unaffected by 5-HT depletion. 8-OH-DPAT strengthened the ASR in IR but not SOC rats and the drug-reduced PPI could be adjusted by 5,7-DHT pretreatment. 8-OH-DPAT at 100 μg/kg enhanced PPI in 5-HT-depleted SOC rats. However for IR rats, 8-OH-DPAT strengthened PPI in sham rats but downgraded it in depletion condition. CONCLUSION: The integrity of central 5-HT system is important to 5-HT1A-modulated sensorimotor gating in isolation-reared rats.
Subject(s)
Animals , Rats , 8-Hydroxy-2-(di-n-propylamino)tetralin , Acoustics , Motor Activity , Prepulse Inhibition , Receptor, Serotonin, 5-HT1A , Reflex, Startle , Sensory Gating , Serotonin , Serotonin 5-HT1 Receptor Agonists , Social Control, FormalABSTRACT
Resumen En esta investigación se evaluaron los efectos de la administración sistémica del antagonista GABAA bicuculina sobre los efectos del agonista 5-HT1A 8-OH-DPAT en las propiedades discriminativas de la anfetamina (ANF) utilizando el condicionamiento de aversión a los sabores. Los resultados mostraron que ni el 8-OH-DPAT, ni la bicuculina, sustituyeron la señal discriminativa de la ANF. Sin embargo, la administración del 8-OH-DPAT disminuyó la señal discriminativa de la ANF, y la administración de la bicuculina, previa a la administración del 8-OH-DPAT más una dosis de ANF, previno el efecto del 8-OH-DPAT sobre la señal discriminativa de la ANF. Estos datos apoyan la hipótesis de que las conductas relacionadas con la adicción a las drogas, como la ANF, involucran diferentes sistemas de neurotransmisión como la DA, la 5-HT y el GABA.
Abstract In this research, the effects of systemic administration of the GABAA receptor antagonist bicuculline on the effects of 5-HT1A receptor agonist 8-OH-DPAT on the discriminative properties of the AMPH using the conditioned taste aversion procedure were evaluated. The results showed that neither 8-OH-DPAT nor bicuculline administration did not substitute for AMPH. However, the 8-OH-DPAT administration decreased the discriminative signal of AMPH and the bicuculline administration, prior to the 8-OH-DPAT administration plus a dose of AMPH prevented the effect of the 8-OH-DPAT on discriminative signal of AMPH. These data support the hypothesis that addiction-related behaviors of drugs such as AMPH involve several neurotransmitter systems such as DA, 5-HT and GABA.
ABSTRACT
El estrés afecta el sistema inmunológico, sin embargo, no hay reportes sobre receptores de serotonina en linfocitos. Se estudiaron los receptores 5-HT1A y la proliferación linfocitaria de ratas macho adultas luego de restricción física. Fueron colocadas en cajas de Plexiglass durante 5 horas diarias por 1, 3 ó 5 días. Se extrajo sangre cardíaca, se aislaron los linfocitos por gradiente de densidades y adhesión al plástico; se cultivaron con el agonista 8-hidroxi-di-n-propil-aminotetralina(8-OH-DPAT) ó el antagonista N-(2-(4-(2-metoxifenil)-1-piperazinetil)-N-(2-piridinil) ciclohexanocarboxamida (WAY-100635) de los receptores 5-HT1A y del mitógeno concanavalina A. La proliferación se midió con sales de tetrazolio. La 8-OH-DPAT no afectó la proliferación. El WAY-100635 disminuyó la proliferación. La restricción física aumentó la sensibilidad al efecto del WAY-100635, lo cual podría deberse a cambios en la expresión o a una modulación funcional de los receptores por efecto del estrés, como se ha reportado previamente en cerebro de rata.
Stress affects the immune system, however, little is known about the effects on specific modifications of lymphocytes serotonin receptors. The effects of restraint stress on the role of 5-HT1A receptors in lymphocyte proliferation were evaluated in male adult rats. They were placed in Plexiglass boxes, during 5 daily hours for 1, 3 or 5 consecutive days. Next day a blood sample was obtained by cardiac punction. Lymphocytes were isolated by density gradient and adhesionto plastic. They were cultured with agonist 8-hydroxy-di-n-propyl-aminotetralin (8-OH-DPAT) or antagonist N-(2-(4-(2-methoxyphenyl)-1-piperazinyl) ethyl)-N-(2-pyridiyl) cyclohexanecarboxamide (WAY-100635) of 5-HT1A receptors and the mitogen concanavalin A. Proliferation was measured by tetrazolium salts. 8-OH-DPAT did not modify cell proliferation; WAY-100635 diminished it. Restraint stress increased the susceptibility to effect of WAY-100635. These results suggest changes in the expression or functional modulation of 5-HT1A receptors in lymphocytes by stress, similar to previous reports on serotonergic system in rat brain.