Phasic firing

Figure 5. The effect of the selective serotonin reuptake inhibitor, escitalopram, on firing activity of norepinephrine neurons. Norepinephrine neurons exhibit tonic-phasic firing activity of 1.5-3.0 Hz, with small (2-3/min) number of short burst ( ). Escitalopram inhibits the firing activity of norepinephrine...

Dutton, A., and Dyball, R.E. Phasic firing enhances vasopressin release from the rat neurohypophysis. J Physiol 1979, 290 433-440. 

Gahwiler, B.H., and Dreifuss, J.J. Transition from random to phasic firing induced in neurons cultured from the hypothalamic supraoptic area. Brain Res 1980,193 415 125. 

Li Z, Hatton GI 1996 Oscillatory bursting of phasically firing rat supraoptic neurones in low-Ca medium Na influx, cytosolic Ca and gap junctions. J Physiol 496 379-394... 

Methylphenidate like cocaine largely acts by blocking reuptake of monoamines into the presynaptic terminal. Methylphenidate administration produces an increase in the steady-state (tonic) levels of monoamines within the synaptic cleft. Thus, DAT inhibitors, such as methylphenidate, increase extracellular levels of monoamines. In contrast, they decrease the concentrations of the monoamine metabolites that depend upon monoamine oxidase (MAO), that is, HVA, but not catecholamine-o-methyltransferase (COMT), because reuptake by the transporter is required for the formation of these metabolites. By stimulating presynaptic autoreceptors, methylphenidate induced increase in dopamine transmission can also reduce monoamine synthesis, inhibit monoamine neuron firing and reduce subsequent phasic dopamine release. 

Floresco S. B., West A. R., Ash B Moore H., Grace A. A. (2003). Afferent modulation of dopamine neuron firing differentially regulates tonic and phasic dopamine transmission. Nat. Neurosci. 6(9), 968-73. 

Activation-synthesis model. (A) Systems model. (B) Wiring diagram. As a result of disinhibition caused by cessation of aminergic neuronal firing, brainstem reticular systems autoactivate. Their outputs have effects including depolarization of afferent terminals causing phasic presynaptic inhibition and blockade of external stimuli, especially during the bursts of REM, and postsynaptic hyperpolarization... 

Adaptation/disadaptation rates determine how phasic a response is (Moore, 1994). Some Drosophila ORNs show amuch slower rise and fall in firing frequency (de Bruyne et al., 2001) and could be considered more tonic. These different responses to onset and duration of stimuli are mimicked by diversity in their response at the end of stimulation (de Bruyne et al., 2001). Some ORNs show an... 

Therefore the firing rate of ORNs is not an exact reflection of the dynamics of odor pulses. More importantly, the temporal correlation of firing with odor concentration differs between ORN classes and between odors that stimulate the same class. This suggests a temporal dimension to the odor code at the level of the ORN population. Getz and Akers (1997) calculated that the information content of the phasic period of ORNs is much higher than the tonic period suggesting odor quality can be assessed relatively fast and is not dependent on the duration of odor pulses. In addition to the instantaneous pattern of activity across ORNs, the comparison of on-off dynamics between ORN classes may also contain information. 

HT4 receptors have been recently demonstrated to exert both a tonic and a phasic, positive, frequency-related control on the firing of NRD 5-HT neurons (202). 

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