Voltage clamp data were analyzed in order to characterize the properties of the fast potassium transient current I(A) for a presumed serotonergic neuron of the rat dorsal raphe nucleus (DRN). We obtain maximal conductance, time constants of activation and inactivation, and the steady state activation and inactivation functions m(∞) and h(∞), as Boltzmann curves, defined by half-activation poten...

Circulating glucocorticoid levels vary with stress and psychiatric illness and play a potentially important role in regulating transmitter systems that regulate mood. To determine whether chronic variation in corticosterone levels within the normal diurnal range altered the control of 5-hydroxytryptamine (5-HT) neuronal activity, male rats were adrenalectomized and implanted with either a 2% or...

The dorsal raphe (DR) nucleus is a system of nuclei in the midline of the lower brainstem, which is considered one of the most important nuclei in the modulation of pain in the central nervous system. Central noradrenergic systems play an important role in the control of cardiovascular regulation and pain transmission. Clonidine, an alpha 2-adrenergic agonist is used extensively in anesthesia r...

Cocaine and amphetamine-regulated transcript peptides (CART) are implicated in the antidepressant effect. This may involve in 5-hydroxytryptamine (5-HT) in the CNS. The aim of the present studies was to investigate the effect of CART peptides on extracellular 5-HT in the dorsal raphe nucleus (DRN) and nucleus accumbens (NAcc) using a microdialysis approach in freely behaving rats. Reverse infus...

In the present study nicotine (0.1 mg/kg, s.c.) increased discharge rate of putative dorsal raphe (DRN) serotonergic neurons of behaving rats during REM sleep (362.61%), without any significant change during waking and non-REM sleep. Since serotonergic DRN neurons gate PGO onset, these results suggest that nicotine-induced suppression of PGO spikes during REM sleep previously reported is achiev...

Involvement of the caudal raphe nuclei (raphe pallidus, RPa; raphe magnus, RMg, and raphe obscurus, ROb) in feeding behavior of adult rats was studied by measuring c-Fos protein expression, in animals submitted to the "meal-feeding" model of food restriction in which the rats were fed ad libitum only from 7:00 to 9:00 h, for 15 days. The experimental groups submitted to chronic fasting, named '...

The serotonergic system plays a key role in the control of impulsive behaviors. Forebrain serotonin depletion leads to premature actions and steepens discounting of delayed rewards. However, there has been no direct evidence for serotonin neuron activity in relation to actions for delayed rewards. Here we show that serotonin neurons increase their tonic firing while rats wait for food and water...

The present studies evaluated the effects of acute and long-term administration of the 5-HT1A agonist BAY x 3702 on the responsiveness of dorsal raphe 5-HT neurons and of dorsal hippocampus CA3 pyramidal neurons. BAY x 3702 potently reduced the firing activity of 5-HT neurons and of CA3 pyramidal neurons when applied by microiontophoresis and this inhibitory effect of BAY x 3702 was fully antag...