Characteristics of GABAergic and cholinergic neurons in perinuclear zone of mouse supraoptic nucleus

Abstract

The perinuclear zone (PNZ) of the supraoptic nucleus (SON) contains some GABAergic and cholinergic neurons thought to innervate the SON proper. In mice expressing enhanced green fluorescent protein (eGFP) in association with glutamate decarboxylase (GAD)65 we found an abundance of GAD65-eGFP neurons in the PNZ, whereas in mice expressing GAD67-eGFP, there were few labeled PNZ neurons. In mice expressing choline acetyltransferase (ChAT)-eGFP, large, brightly fluorescent and small, dimly fluorescent ChAT-eGFP neurons were present in the PNZ. The small ChAT-eGFP and GAD65-eGFP neurons exhibited a low-threshold depolarizing potential consistent with a low-threshold spike, with little transient outward rectification. Large ChAT-eGFP neurons exhibited strong transient outward rectification and a large hyperpolarizing spike afterpotential, very similar to that of magnocellular vasopressin and oxytocin neurons. Thus the large soma and transient outward rectification of large ChAT-eGFP neurons suggest that these neurons would be difficult to distinguish from magnocellular SON neurons in dissociated preparations by these criteria. Large, but not small, ChAT-eGFP neurons were immunostained with ChAT antibody (AB144p). Reconstructed neurons revealed a few processes encroaching near and passing through the SON from all types but no clear evidence of a terminal axon arbor. Large ChAT-eGFP neurons were usually oriented vertically and had four or five dendrites with multiple branches and an axon with many collaterals and local arborizations. Small ChAT-eGFP neurons had a more restricted dendritic tree compared with parvocellular GAD65 neurons, the latter of which had long thin processes oriented mediolaterally. Thus many of the characteristics found previously in unidentified, small PNZ neurons are also found in identified GABAergic neurons and in a population of smaller ChAT-eGFP neurons.

Angiotensin Type-2 Receptors Influence the Activity of Vasopressin Neurons in the Paraventricular Nucleus of the Hypothalamus in Male Mice

“…Of relevance, several studies have used either the AT2R antagonist, PD123319, or AT2R knockout mice to demonstrate that, at the doses used in the present study, C21 exerts AT2R-specific effects (47)(48)(49)(50). Initial patch-clamp electrophysiological studies revealed that AT2R-expressing neurons in the peri-PVN shared similar general electrophysiological properties to previously described hypothalamic interneurons, including GABAergic ones, such as the expression of a rebound LTS and a mostly linear current/voltage relationship (51,52). Importantly, we found that activation of AT2R with the selective agonist C21 excites AT2R-eGFP neurons in the peri-PVN area, evoking and/or increasing their firing discharge.…”

Oxytocin Neurones: Intrinsic Mechanisms Governing the Regularity of Spiking Activity

“…This suggests that, in the experimental conditions, apamin also had presynaptic actions, either reducing excitatory input or increasing inhibitory input. The latter is more likely because the actions of apamin would be generally expected to increase neuronal excitability, increasing spike rate as is observed in vitro (34), and supraoptic neurones receive an extensive inhibitory input from GABA neurones in the perinuclear zone immediately adjacent to the supraoptic nucleus (35,36).…”

Electrophysiological properties of identified oxytocin and vasopressin neurones

“…The I A underlies the prominent transient outward rectification (TOR) that delays spike activation in magnocellular PVN and SON neurones when depolarised from hyperpolarised membrane potentials, contributes to spike repolarisation, and likely plays a significant role in somatic and terminal spike broadening (ie, which facilitates Ca 2+ influx) via its activity‐dependent inactivation. The strong presence of TOR in the magnocellular neurones distinguishes them from many surrounding parvocellular neurones in the PVN and SON . Most SON neurones are immunopositive for an A‐type channel subunit, KV4.2 .…”