Stimulation of H₃-Histamine Receptors Increases the Release of Prolactin in Male Rats

Abstract

Histamine (HA) stimulates prolactin secretion via H₁ and H₂ receptors. In the present study, we examined the role of a third subtype of receptor recently described in brain, the H₃-HA receptor, on prolactin secretion in male rats. R(-)α-methyl-HA (α-MHA), a selective H₃ receptor agonist, was injected into the lateral ventricle of the brain in freely moving rats. α-MHA produced a dose-dependent (1-5 µg) and long-lasting increase in plasma prolactin levels. This increase was observed from 15 to 60 min after injection of α-MHA. Its stimulatory action was prevented by thioperamide (20 µg i.v.t), a selective H₃ antagonist. This compound, injected intraventricularly, lacked effect by itself on basal plasma prolactin levels. Neither pyrilamine (Hi antagonist; 60 µg i.v.t.) nor ranitidine (H₃ antagonist; 60 µg i.v.t.) affected α-MHA-induced prolactin release. The stimulatory effect was still present when brain HA was depleted by α-fluoromethylhistidine (30 mg/kg i.p.). Our findings suggest that α-MHA evokes prolactin release by activation of postsynaptic H₃ receptors.

Not Itself Histamine, but H3R Antagonists/Inverse Agonist Thioperamide Enhances Long-term Potentiation in the Dentate Gyrus of Urethane- Anesthetized Rats

“…Indeed, there is fragmentary evidence pointing to possible existence of postsynaptic H3Rs. Such conclusion is arrived at when agonist stimulation of the H3R produces the same outcome as a parallel experiment, in which the targeted effectors (histamine or otherwise) are exogenously administered or suppressed [43]. Suggesting this conclusion, when we infused histamine we observed an increase in EPSP-LTP, in a similar way as thioperamide, although the difference between the control and histamine groups remained trend level.…”

Effect of modified brain histamine contents on prolactin and thyrotropin secretion in male rats

“…For each experiment, 20 HamWist rats weighing 200-2 50 g were decapitated and the APs dissected and sliced on ice. The AP fragments were stirred in a trypsinizing flask for 30min at +37°C in DMEM/F12 medium (50 ml) containing 5 mg/ml of collagenase (Sigma Type If) and 0.1 mg/ml of DNAse (Sigma Type I).…”

“…a-Fluoromethylhistidine inhibits stress-induced pro¬ lactin surges (17,18) and morphine-induced prolactin secretion (19), but has no effect on basal prolactin secretion (18,20) in conscious male rats. Large doses of L-histidine given ip (21, 22) inhibit cold-stimulated TSH secretion.…”

Modulation of behavior by the histaminergic system: Lessons from HDC-, H3R- and H4R-deficient mice

“…Another layer of complexity may be added by postsynaptically localized H 3 R (Fig. 1) that did not receive much attention in H 3 R research during the past years, but the existence of which was repeatedly reported in literature (Navarro et al, 1993;Malinowska et al, 1998;Gastinger et al, 2006;Arrang et al, 2007;Ferrada et al, 2008). An excellent review on the function of postsynaptic H 3 R in the basal ganglia was recently published by Ellenbroek and Ghiabi (2014).…”