Neuroscience
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Comparative Study
Molecular and functional analysis of hyperpolarisation-activated nucleotide-gated (HCN) channels in the enteric nervous system.
Hyperpolarisation-activated non-specific cation currents (Ih currents) are important for the regulation of cell excitability. These currents are carried by channels of the hyperpolarisation-activated nucleotide-gated (HCN) family, of which there are four known subtypes. In the enteric nervous system (ENS), the Ih current is prominent in AH neurons. ⋯ There was no correlation between the magnitude of the Ih and intensity of channel immunoreactivity. Our results indicate that HCN1, 2 and 4 genes and protein are expressed in the ENS. AH/Dogiel type II neurons, which have a prominent Ih, express HCN2 and 4 in guinea-pig and HCN1 and 2 in mouse and rat.
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Comparative Study
Synaptic properties and postsynaptic opioid effects in rat central amygdala neurons.
An important output of amygdaloid nuclei, the central nucleus of the amygdala (CeA) not only mediates negative emotional behaviors, but also participates in the stimulus-reward learning and expression of motivational aspects of many drugs of abuse, and links environmentally stressful conditions such as fear to endogenous pain-inhibiting mechanisms. The endogenous opioid system in the CeA is crucial for both reward behaviors and environmental stress-induced analgesia. In this study using whole-cell voltage-clamp recordings, we investigated synaptic inputs and the postsynaptic effects of opioid agonists in CeA neurons. ⋯ In contrast, the kappa-opioid receptor agonist hyperpolarized only type B neurons. These results illustrate three types of CeA neurons with distinctive membrane properties and differential responses to opioid agonists. They may represent functionally distinct CeA cell groups for the integration and execution of CeA outputs in the aforementioned CeA functions.
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Comparative Study
Early stages of memory formation in filial imprinting: Fos-like immunoreactivity and behavior in the domestic chick.
Early stages of memory formation in filial imprinting were studied in domestic chicks. Chicks trained for 15 min showed strong imprinting, demonstrated by a strong preference for their training stimulus, and the time course of this preference over 2 days after training was similar to that of chicks trained for 60 min. The chicks therefore learned characteristics of the training stimulus very early during training. ⋯ The time course of expression was stimulus-dependent. Fos expression in the IMHV, but not the hippocampus, was significantly correlated with strength of imprinting. It is concluded that the learning-specific change in Fos expression in the IMHV is associated with very early components of memory formation.
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Comparative Study
Carbachol in the pontine reticular formation of C57BL/6J mouse decreases acetylcholine release in prefrontal cortex.
The prefrontal cortex and brainstem modulate autonomic and arousal state control but the neurotransmitter mechanisms underlying communication between prefrontal cortex and brainstem remain poorly understood. This study examined the hypothesis that microdialysis delivery of carbachol to the pontine reticular formation (PRF) of anesthetized C57BL/6J (B6) mouse modulates acetylcholine (ACh) release in the frontal association cortex. Microdialysis delivery of carbachol (8.8 mM) to the PRF caused a significant (P<0.01) decrease (-28%) in ACh release in the frontal association cortex, a significant (P<0.01) decrease (-23%) in respiratory rate, and a significant (P<0.01) increase (223%) in time to righting after anesthesia. ⋯ In vitro treatment with carbachol (1 mM) caused a significant (P<0.01) increase in [(35)S]GTPgammaS binding in the frontal association cortex (62%) and basal forebrain nuclei including medial septum (227%), vertical (210%) and horizontal (165%) limbs of the diagonal band of Broca, and substantia innominata (127%). G protein activation by carbachol was concentration-dependent and blocked by atropine, indicating that the carbachol-stimulated [(35)S]GTPgammaS binding was mediated by muscarinic cholinergic receptors. Together, the in vitro and in vivo data show for the first time in B6 mouse that cholinergic neurotransmission in the PRF can significantly alter ACh release in frontal association cortex, arousal from anesthesia, and respiratory rate.
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Comparative Study
Potential pathways for intercellular communication within the calbindin subnucleus of the hamster suprachiasmatic nucleus.
In mammals, the suprachiasmatic nucleus (SCN) is the master circadian pacemaker. Within the caudal hamster SCN, a cluster of neurons containing the calcium binding protein, calbindin-D28K (CB), has been implicated in circadian locomotion. However, calbindin-immunoreactive (CB+) neurons in the calbindin subnucleus (CBsn) do not display a circadian rhythm in spontaneous firing [Eur J Neurosci 16 (2002) 2469]. ⋯ Lastly, we show that CB+ neurons are coupled to CB+ and CB- neurons by gap junctions. The current study provides a structural framework for synaptic communication, electrical coupling, and signaling via a growth factor within the CBsn of the hamster SCN. Our results reveal connections that have the potential for integrating cellular communication within a subregion of the SCN that is critically involved in circadian locomotion.