Internal State: Dynamic, Interconnected Communication Loops Distributed Across Body, Brain, and Time.

Internal state profoundly alters perception and behavior. For example, a starved fly may approach and consume foods that it would otherwise find undesirable. A socially engaged newt may remain engaged in the presence of a predator, whereas a solitary newt would otherwise attempt to escape.

Calcium-induced calcium release activates spontaneous miniature outward currents in newt medullary reticular formation neurons.

Neurons in the medullary reticular formation are involved in the control of postural and locomotor behaviors in all vertebrates. Reticulospinal neurons in this brain region provide one of the major descending projections to the spinal cord. Although neurons in the newt medullary reticular formation have been extensively studied using in vivo extracellular recordings, little is known of their intrinsic biophysical properties or of the underlying circuitry of this region.

Corticosterone suppresses vasotocin-enhanced clasping behavior in male rough-skinned newts by novel mechanisms interfering with V1a receptor availability and receptor-mediated endocytosis.

In rough-skinned newts, Taricha granulosa, exposure to an acute stressor results in the rapid release of corticosterone (CORT), which suppresses the ability of vasotocin (VT) to enhance clasping behavior. CORT also suppresses VT-induced spontaneous activity and sensory responsiveness of clasp-controlling neurons in the rostromedial reticular formation (Rf). The cellular mechanisms underlying this interaction remain unclear.

Suppression of sex behavior by kappa opiates and stress steroids occurs via independent neuroendocrine pathways.

Endocannabinoids and their receptors are found throughout the brain of all vertebrates. By virtue of their wide distribution, endocannabinoids have the potential to affect many behaviors. Prior research has shown that cannabinoids inhibit courtship-clasping and mediate behavioral responses to stress in male rough-skinned newts, Taricha granulosa, and cannabinoid signaling is initiated by rapid actions of the steroid corticosterone (CORT) at its specific membrane receptor (mCR).

Lithium modulates cortical excitability in vitro.

The sometimes devastating mood swings of bipolar disorder are prevented by treatment with selected antiepileptic drugs, or with lithium. Abnormal membrane ion channel expression and excitability in brain neurons likely underlie bipolar disorder, but explaining therapeutic effects in these terms has faced an unresolved paradox: the antiepileptic drugs effective in bipolar disorder reduce Na(+) entry through voltage-gated channels, but lithium freely enters neurons through them. Here we show that lithium increases the excitability of output neurons in brain slices of the mouse olfactory bulb, an archetypical cortical structure.

All-or-none population bursts temporally constrain surround inhibition between mouse olfactory glomeruli.

With each sniff, the olfactory bulbs of the brain generate a neural activity pattern representing the odour environment, transmitting this to higher brain centres in the form of mitral cell output. Inhibitory circuits in the olfactory bulb glomerular and external plexiform layers may amplify contrast in these patterns, through surround inhibition of mitral cells. These circuits may operate in series, but their respective roles are unclear.

Endocannabinoids mediate the effects of acute stress and corticosterone on sex behavior.

For animals in the wild, survival depends on being able to detect and respond rapidly to danger by switching from risky (e.g. conspicuous courtship) to survival-oriented behaviors.

Neuroanatomical distribution of cannabinoid receptor gene expression in the brain of the rough-skinned newt, Taricha granulosa.

Type I cannabinoid receptor (CB1) is a G-protein coupled receptor with a widespread distribution in the central nervous system in mammals. In a urodele amphibian, the rough-skinned newt (Taricha granulosa), recent evidence indicates that endogenous cannabinoids (endocannabinoids) mediate behavioral responses to acute stress and electrophysiological responses to corticosterone. To identify possible sites of action for endocannabinoids, in situ hybridization using a gene and species specific cRNA probe was used to label CB1 mRNA in brains of male T.

Neuroendocrinology of context-dependent stress responses: vasotocin alters the effect of corticosterone on amphibian behaviors.

The ability of an animal to respond with appropriate defensive behaviors when confronted with an immediate threat can affect its survival and reproductive success. In the roughskin newt (Taricha granulosa), exogenous corticosterone (CORT) rapidly blocks and vasotocin (VT) enhances reproductive behaviors (mainly clasping behavior). Electrophysiological studies have shown that pretreatment of male Taricha with VT counteracts the inhibitory effects of CORT on neuronal activity in the medulla.